Christine Faille

Charles Cunault

Thomas Dubois

Thierry Benezech
email: thierry.benezech@lille.inra.fr

Thierry Bénézech

Hygienic design of food processing lines to mitigate the risk of bacterial food contamination with respect to environmental concerns

Keywords: Surface hygiene, cleanability, bacterial food contaminants, biofilms, drying Highlights •

diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Introduction

Foodborne diseases are considered an emergent public health concern throughout the world. Food contact surfaces in processing equipment are considered to be major factors in the risk of food contamination in the food and beverage industries. Joint responsibility of equipment manufacturers and food producers could be suggested. Hence surface hygiene concerns could be tackled both by looking at the machinery design (geometry and material) and at the cleaning and disinfection operation conditions and frequencies.

Over recent years, apart from numerous studies of surface disinfections, great interest has been shown in both the mechanisms of (i) surface contamination, including the potential roles of materials and environmental conditions and of (ii) surface cleaning, largely governed by the machinery design impacting the mechanical action of the detergent flow under cleaning-in-place (CIP) conditions.

Another constraint for the food industries today, is the reduction of environmental impacts, all the more so, as cleaning operations are largely concerned in this issue.

The understanding of all the mechanisms involved in soiling and cleaning operations would provide combined strategies for providing cost effective results, without causing any adverse effect on human health or the environment. The purpose of this paper is to gather together all of the relevant insights from most of the recent studies to better decipher and hopefully, solve such issues.

Substrata: Role of material properties on bacterial contamination and detachment

Even when hygiene procedures are applied, adherent micro-organisms can be observed on every surface of food-industry plants, including stainless steel surfaces, gaskets, floors, conveyors belts or equipment. The ability of micro-organisms to contaminate these surfaces varies greatly according to the substratum composition. Indeed, differences are frequently observed in the ease with which bacteria not only adhere to materials [START_REF] Lelièvre | Cleaning in place: modelling of cleaning Kinetics of pipes soiled by Bacillus spores assuming a process combining removal and deposition[END_REF], but also form biofilms (Somers & Wong, 2004). One reason given is that some of the substratum components, such as the nickel in some stainless steel alloys [START_REF] Lopes | The influence of nickel on the adhesion ability of Desulfovibrio desulfuricans[END_REF], or the elastomer NBR (Storgards, Simola, Sjoberg, & Wirtanen, 1999) would impact the physiology (growth or viability) of adherent bacteria. Furthermore, Comment citer ce document : Faille, C., Cunault, C., Dubois, T., Bénézech, T. (Auteur de correspondance) (2018). Hygienic design of food processing lines to mitigate the risk of bacterial food contamination with respect to environmental concerns. Innovative Food Science and Emerging Technologies, 46 (SI), 65-73.

, DOI : 10.1016/j.ifset.2017.10.002

A C C E P T E D M A N U S C R I P T 4 the nature of the materials would also clearly affect the ease of removal of adherent bacteria and biofilms and consequently the hygienic properties of the substrata. Reported works have highlighted that bacterial detachment was easier from stainless steel than from other substrata such as PEHD, Teflon®, PVC… [START_REF] Midelet | Transfer of microorganisms, including Listeria monocytogenes, from various materials to beef[END_REF]Somers & Wong, 2004), but differences have also been identified between polymers [START_REF] Sénéchal | Probing surface adhesion forces of Enterococcus faecalis to medical-grade polymers using atomic force microscopy[END_REF]. Along with their chemical composition, surface properties of materials used in the food industry also vary greatly. Some of them, e.g. physico-chemistry and topography, have been assumed to affect interactions between micro-organisms and materials, in terms of surface contamination and/or further ease of cleaning. It is worth noting that these surface properties may change over time, due to surface conditioning and/or of surface ageing.

Physicochemistry

Contrarily to what happens between cells and plant or animal tissues, the interactions between materials and micro-organisms are driven by physicochemical interactions, e.g.

acid-base, electrostatic or hydrophobic interactions. Two major theories involving these physicochemical interactions have been proposed for predicting the level of bacterial attachment to inert surfaces. The Derjaguin-Landau-Verwey-Overbeek (DLVO) theory describes the total Gibbs energy of interaction between a microorganism and a surface as a function of the separation distance [START_REF] Hermansson | The DLVO theory in microbial adhesion[END_REF]. The thermodynamic theory is based on the comparison of the interfacial surface free energies for bacteria in suspension and bacteria in an adhered state (van Oss, 2006).

First of all, it is noteworthy that in most environmental conditions (neutral pH), bacteria are negatively charged, as are most of the substrata (stainless steel, glass, polymers). Consequently, repulsive interaction generally occurs, lowering bacterial adhesion, as demonstrated in a few works, by using positively-and negatively-charged materials [START_REF] Mi | pH responsive properties of nonfouling mixed-charge polymer brushes based on quaternary amine and carboxylic acid monomers[END_REF]Terada et al., 2005), or by suspending media of low and high ionic strength [START_REF] Li | Bacterial adhesion to glass and metal-oxide surfaces[END_REF]. Conversely, the subsequent colonisation could be inhibited on positively-charged surfaces because of strong interactions between bacteria and substratum which would impair cell division [START_REF] Gottenbos | Antimicrobial effects of positively charged surfaces on adhering Gram-positive and Gram-negative bacteria[END_REF].

Along with these interactions, hydrophobic interactions are also supposed to play a major role, due to the unusually strong attraction of hydrophobic surfaces in water [START_REF] Meyer | Recent progress in understanding hydrophobic interactions[END_REF]. According to van Oss (Van Oss, 1997), hydrophobic interactions would even be the strongest long-range non-covalent interactions in biological systems. However, even if much has

Comment citer ce document : Faille, C., Cunault, C., Dubois, T., Bénézech, T. (Auteur de correspondance) (2018). Hygienic design of food processing lines to mitigate the risk of bacterial food contamination with respect to environmental concerns. Innovative Food Science and Emerging Technologies, 46 (SI), 65-73.

, DOI : 10.1016/j.ifset.2017.10.002

A C C E P T E D M A N U S C R I P T 5 been written on the role of substratum hydrophobicity in the attachment of bacteria and in the formation of biofilms, there are a number of inherent contradictions. The bacterial adhesion, interaction strength (Xiaoxia, Peng, & Olavi, 2006) and ease of removal of adherent bacteria (Boulangé-Petermann, Gabet, & Baroux, 2006;[START_REF] Sénéchal | Probing surface adhesion forces of Enterococcus faecalis to medical-grade polymers using atomic force microscopy[END_REF] has often been reported to be impaired on hydrophobic substrata, but other reports suggest that hydrophobic substrata would promote bacterial adhesion, given the greater extent of bacterial adhesion (Cerca, Pier, Vilanova, Oliveira, & Azeredo, 2005), or the higher resistance to cleaning procedures of Bacillus spores, whatever the spore wettability [START_REF] Lelièvre | Cleaning in place: modelling of cleaning Kinetics of pipes soiled by Bacillus spores assuming a process combining removal and deposition[END_REF]. These discrepancies could be, at least in part, relevant to bacterial properties, e.g. the presence of fimbriae (Otto et al., 1999), or of a mucous layer [START_REF] Faille | Presence and function of a thick mucous layer rich in polysaccharides around Bacillus subtilis spores[END_REF]. Conversely, only a few works have suggested that biofilm development and structure are affected by the substratum hydrophobicity [START_REF] Patel | S. epidermidis biofilm formation: effects of biomaterial surface chemistry and serum proteins[END_REF][START_REF] Ploux | Quantitative and morphological analysis of biofilm formation on self-assembled monolayers[END_REF]. Concerning surface free energies, little hard evidence has been published stating that substratum surface energy is correlated to bacterial adhesion [START_REF] Hüsmark | Adhesion of Bacillus cereus spores to different solid surfaces : cleaned or conditioned with various food agents[END_REF][START_REF] Ong | Adhesion forces between E. coli bacteria and biomaterial surfaces[END_REF]Vadillo-Rodríguez, Busscher, Van Der Mei, De Vries, & Norde, 2005). This lack of correlation would be the result of a non-linear relationship, with a lowest adhesion for intermediate values of the surface free energy (20-30 mJ m -2 ), as shown in reported works [START_REF] Pereni | Surface free energy effect on bacterial retention[END_REF]Tang et al., 2009;Zhao, Wang, Liu, & Wang, 2007).

The difficulty in attributing a specific role to each of the physicochemical interactions might be related to the coupling of several interactions in bacterial adhesion and biofilm formation (Sheng, Ting, & Pehkonen, 2007). One could also hypothesize that the discrepancies observed between models and real phenomena would reflect non-homogeneous surface free energies, that would provide localized sites favourable for bacterial attachment or retention, for example on stainless steel grain boundaries [START_REF] Geesey | The influence of surface features on bacterial colonization and subsequent substratum chemical changes of 316L stainless steel[END_REF]. Indeed, micro-or nano-scale heterogeneities in substratum physicochemistry have been proven to affect bacterial adhesion (Bos, van der Mei, Gold, & Busscher, 2000;[START_REF] Kalasin | The role of nano-scale heterogeneous electrostatic interactions in initial bacterial adhesion from flow: A case study with Staphylococcus aureus[END_REF]. At PIHM, the central role of surface micro-heterogeneities on Bacillus spore adhesion was displayed [START_REF] Galopin | Selective adhesion of Bacillus cereus spores on heterogeneously wetted silicon nanowires[END_REF]. Indeed, an accumulation of spores was clearly observed at the borders of the superhydrophilic/superhydrophobic patterns (Figure 1). However, these aspects have been currently poorly investigated, despite their possible consequences in terms of bacterial contamination of heterogeneous substrata, or of border areas between different materials in contact.

To add further complexity and to render the comprehension of interfacial phenomena even more challenging, the substratum is continually subjected to surface conditioning resulting from the rapid adsorption of materials from the liquids in contact (proteins, fat, minerals, detergents, surfactants, disinfectants, etc.). The formation of the so-called conditioning film may strongly affect not only the surface physico-chemistry (such as the basic polar component) of materials, but also their hygienic properties. In order to investigate the influence of this conditioning film on substratum properties, Jullien et al. [START_REF] Jullien | Physico-chemical and hygienic property modifications of stainless steel surfaces induced by conditioning with food and detergent[END_REF] subjected stainless steel surfaces to up to 25 successive soiling (with milk or meat) and cleaning (with detergent) runs in a pilot rig. They observed a significant decrease in the hygienic status of the stainless steel surfaces for both conditioning procedures (milk or meat), but the decrease was more marked when milk was used. Other reported works have also demonstrated that conditioning conditions strongly affected further bacterial surface contamination, yet that the modifications resulting from this conditioning film were bacteria-dependent [START_REF] Palmer | Bacterial cell attachment, the beginning of a biofilm[END_REF].

To conclude, the composition/structure of the conditioning film is closely dependant on environmental conditions, e.g. nature of foods and detergents in contact, fluid temperature… In other words, the physicochemistry and consequently the surface hygiene of materials found in food environments may change radically, depending on the food chain and the processes in place.

Topography

In addition to the physicochemical properties, substratum topography has been recognized to largely influence bacterial contamination. Indeed, in industrial plants it is common to find materials with an irregular surface, some of which are poorly accessible and difficult to clean, such as gaskets or complex pieces of equipment [START_REF] Lemos | The effect of shear stress on the formation and removal of Bacillus cereus biofilms[END_REF] and these areas are often associated with a persistence of bacterial contamination.

Intuitively, one can assume that surface areas available for bacterial attachment or growth are greater on rougher surfaces and that topographic features provide protection to adhered bacteria from shear forces, as for instance during cleaning procedures. However, despite the volume of results available in the literature, the mechanisms by which surface topography modulates bacterial contamination remain largely unclear. The inconsistencies in the published results might be primarily due to the fact that, in most reported works, the surface topography was solely described by the parameter Ra (average roughness, arithmetical mean deviation of the absolute ordinate values within a sampling length). For example, some results suggested that bacterial adhesion/colonisation of stainless steel surfaces (Ra ranging from 0.06 to 0.89 µm) decreases with Ra, until a threshold average roughness of 0.16 μm, below which no further reduction could be expected [START_REF] Medilanski | Influence of the surface topography of stainless steel on bacterial adhesion[END_REF], while others [START_REF] Hilbert | Influence of surface roughness of stainless steel on microbial adhesion and corrosion resistance[END_REF] failed to observe any effect on the adhesion and removal by a cleaning procedure (Ra ranging from 0.01 to 0.9 µm). This is doubtlessly partially linked to the fact that Ra is unable to account for the shape of the surface irregularities, or even the presence of some rare irregularities despite their role in surface hygiene. For example, in a work published by Faille et al. [START_REF] Faille | Influence of physicochemical properties on the hygienic status of stainless steel with various finishes[END_REF], two stainless steel surfaces characterized by different topographies (periodic roughness profile with regular waves, vs irregular profile without any organisation but with many pits and valleys) exhibited similar Ra values (+/-1.15 µm), but quite different hygienic statuses. Furthermore, adherent bacteria have been often associated with surface features similar in size to, or slightly larger than the cells or spores involved, as observed in the bottom of crevices (Díaz, Schilardi, Salvarezza, & De Mele, 2007), or in the depth of the grain boundaries and crevices (personal communication, Figure 2). We may assume that surfaces with features of microbial sizes may retain bacteria in greater numbers than smoother or rougher surfaces by increasing the exchange surface with adherent bacteria and providing a better protection from shear forces.

The relevance of other roughness parameters than Ra, such as those derived from the Abbot-Firestone curve was investigated. These parameters such as the reduced valley depth (Rvk), the reduced peak height (Rpk described in the standard ISO 13565-2 (1997), or the levelling depth (Rp) described in the standard DIN 4762 (1989) better take into account the presence and shape of peaks and valleys on the substratum surface and have been proven to be better linked to the hygienic status of the materials [START_REF] Faille | Influence of physicochemical properties on the hygienic status of stainless steel with various finishes[END_REF][START_REF] Jullien | Identification of surface characteristics relevant to the hygienic status of stainless steel for the food industry[END_REF].

It is important to consider that the above studies often involved different material types with a wide range of shapes and sizes of surface features, which are spread more or less randomly over the whole surface. In order to gain the best possible understanding of the role of specific features in bacterial adhesion, surfaces with regular, well-defined topographical patterns were produced and investigated for their hygienic status. Works

Comment citer ce document : Faille, C., Cunault, C., Dubois, T., Bénézech, T. (Auteur de correspondance) (2018). Hygienic design of food processing lines to mitigate the risk of bacterial food contamination with respect to environmental concerns. Innovative Food Science andEmerging Technologies, 46 (SI), 65-73. , DOI : 10.1016/j.ifset.2017.10.002

A C C E P T E D M A N U S C R I P T 8
reported by Whitehead and Verran were among the first involving these kind of patterned surfaces. Using microbial retention assays with a panel of differently sized micro-organisms, they determined that the sizes of both surface defects and bacterial cells significantly affected the resistance to removal of adherent bacteria (Whitehead, Colligon, & Verran, 2005). More recently, Perera-Costa et al. [START_REF] Perera-Costa | Studying the influence of surface topography on bacterial adhesion using spatially organized microtopographic surface patterns[END_REF] showed that spatially organised micro-topographic surface patterns reduced bacterial adhesion (30-45%) relative to the smooth control samples, whatever the bacterial shape or surface energy.

Unfortunately, despite the lack of data available in the literature, it is highly likely that the presence of micro-and nano-sized topographical features may increase the retention of organic matter which in turn would affect interaction between bacteria and substrata.

Therefore, further study needs to be carried out to validate the effectiveness of patterned materials after an accumulation either of complex food residues or polymeric substances produced by biofilms.

Geometry: flow dynamic roles from surface contamination to surface cleaning

Surface contamination

Hydrodynamic conditions are known to impact biofilm dynamics at any stage, from the adhesion step to the appearance of fully developed biofilms. Much literature is available on this topic, mainly in environmental sciences. Very recently, Lemos et al. (2016) and Araujo et al. (2015) have shown the effect of the hydrodynamic conditions under which biofilms were formed on selected macromolecular characteristics, demonstrating that higher flow velocities can give rise to more complex and denser biofilms. More than 20 years before, [START_REF] Blel | Effect of flow arrangement on the removal of Bacillus spores from stainless steel equipment surfaces during a Cleaning In Place procedure[END_REF], would probably deeply affect the initial contamination and the further biofilm growth dynamics as demonstrated in the recent study by [START_REF] Araujo | Influence of flow velocity on the characteristics of Pseudomonas fluorescens biofilms[END_REF].

Surface cleaning

In closed processing lines, the microbial safety of the products must be ensured by efficient hygienic procedures using Cleaning In Place (CIP) processes. However, the literature shows that some bacterial contamination does remain on equipment surfaces after standard CIP procedures (Elevers et al., 1999). It is now commonplace to consider the definite role of the wall shear stress on the cleaning efficiency. Models were proposed to describe the microbial removal integrating this parameter in the past [START_REF] Lelièvre | Cleaning in place: modelling of cleaning Kinetics of pipes soiled by Bacillus spores assuming a process combining removal and deposition[END_REF]. However, accounting for two-"species" removal, with each of the "species" removal being described by first order kinetics. The phenomenon was described as a removal of two differing adherent bacteria sub-populations with constant rates in relation to their poorly or highly adherent properties. Chemical action or mechanical actions alone appeared to be far less effective that a combination of the two. The poorly adherent population removal constant rate was found to be doubled when comparing CIP and rinsing conditions, the flow rate being the same. More interesting was the very low value of the removal constant rate of the "strongly attached sub-population", being up to 100 times lower than the removal constant rate of the "poorly attached population". Consequently, a 30 min cleaning appeared to be insufficient to remove all of the surface contamination. An example of the removal kinetics thus observed is presented in Figure 3.

Role of areas in contact with air: interface air-liquid-material, drying of contaminated surfaces

A number of other conditions found in food environments could influence the bacterial surface contamination or further cleanability. Such is notably the case regarding the presence of interfaces between substratum, liquid and air. Indeed, several reports on the bacterial contamination of partially immersed surfaces have indicated that the interface between air and liquid would be favourable to bacterial adhesion, as well as to the formation and/or the persistence of biofilms [START_REF] Giaouris | The adherence of Salmonella enteritidis PT4 to stainless steel: The importance of the air-liquid interface and nutrient availability[END_REF][START_REF] Liu | Biofilm Formation characteristics of 24 Pseudomonas lundensis isolated from meat[END_REF]Wijman, de Leeuw, Moezelaar, Zwietering, & Abee, 2007). One can easily imagine that the Comment citer ce document : Faille, C., Cunault, C., Dubois, T., Bénézech, T. (Auteur de correspondance) (2018). Hygienic design of food processing lines to mitigate the risk of bacterial food contamination with respect to environmental concerns. Innovative Food Science and Emerging Technologies, 46 (SI), 65-73.

, DOI : 10.1016/j.ifset.2017.10.002

A C C E P T E D M A N U S C R I P T

13 oxygen availability at the air/liquid interface would contribute to this preferential location of biofilms. As an example, Salmonella enteritidis produced between 2 and 3 log more biofilm on half-immersed stainless steel coupons, as compared to wholly-immersed coupons [START_REF] Giaouris | The adherence of Salmonella enteritidis PT4 to stainless steel: The importance of the air-liquid interface and nutrient availability[END_REF]. Similar observations were made on B. cereus strains (Wijman et al., 2007), which clearly form biofilms at the interface between the liquid and air in wells of microtiter plate assays, but also on partially-immersed stainless steel coupons. The differences between wholly-and half-immersed coupons was of the same order as above, which means that the local bacterial concentration at the air-liquid interface biofilm will be even higher, notably up to 10 8 cells cm -2 . Along with the oxygen availability, it was suggested that motility is a key element of biofilm formation at the air-liquid interface [START_REF] Majed | Bacillus cereus biofilms-same, only different[END_REF]. In conditions close to those encountered in fresh-cut food processing equipment, the air/liquid/wall interface was also shown to be particularly favourable to surface contamination (Cunault et al., 2015). More interestingly, the structure of the biofilm formed by P. fluorescens greatly differed in both environments as observed by SEM (Figure 4): Huge, thick patches were easily observed at the interface between air and liquid, while the potential for biofilm growth was limited on submerged areas. As a consequence, industrial storage and piping systems, which are partly filled during process or where residual liquid has remained after a production cycle (mainly if inadequately cleaned), are conducive to biofilm formation (Wijman, de Leeuw, Moezelaar, Zwietering, & Abee, 2007) and would contribute to recurrent contamination of food during further production cycles.

Furthermore, many bacterial soils undergo a drying step in food environments, which can occur during the production phase or between the production phase and the hygiene procedure. That is the case, for instance, on open surfaces such as conveyor belts, cutting boards, or once again at the air-liquid interface on surfaces of partly-filled equipment, including tanks, pumps, or piping systems. Unfortunately, many bacteria are able to withstand these periods of desiccation, whether in the form of biofilms (Halavi & Hansen, 2013) or of adherent cells [START_REF] Kusumaningrum | Survival of foodborne pathogens on stainless steel surfaces and cross-contamination to foods[END_REF] Zoueshtiagh, 2016), the cleanability of adherent Bacillus spores was proven to be significantly lowered when subjected to a drying step, both time and temperature playing a significant role in the resistance to detachment (Figure 5). Several hypotheses have been put forward to explain this phenomenon. Among these, the shape of the liquid bridge between the sphere and the substratum, could play a major role in the interaction force between bacteria and substrata. The authors also demonstrated that the shape of the liquid bridge, which determines the pressure inside the liquid, and therefore the type of interaction between the particle and the substratum (attraction vs repulsion), was greatly influenced by the hydrophilic/hydrophobic characters of the two surfaces. The physico-chemistry of the substratum would therefore play a role in the various phenomena occurring at the interfaces between bacteria and materials. The areas where drying process occur must therefore be of concern in the hygiene management in the food industries.

Sustainability of cleaning operations in the food and beverage industries

It is generally admitted that the cleaning process efficiency generally depends on four This has prompted investigations into pulsed flow, where a significant change in velocity is imposed on a steady flow either intermittently or continuously.

Based on the major role of the flow perturbation in the cleaning efficiency, the effects of pulsating turbulent flow conditions in the cleaning efficiency were investigated by [START_REF] Gillham | Enhanced cleaning of whey protein soils using pulsed flows[END_REF] showing the increase in both mass transfer and wall shear stresses in pipe flows.

More recently, [START_REF] Bode | Adhesion of Bacillus spores and Escherichia coli cells to inert surfaces : role of surface hydrophobicity[END_REF] showed the effect of the waviness ratio between the amplitude of velocity pulse and the baseline flow velocity on the cleaning time of milk-type deposits. Blel et al. (2009a) an efficient biofilm removal method. Today, such a technique cannot replace current cleaning operations, but could be of help in reducing the criticality of some areas in processing lines, allowing milder cleaning conditions for the whole processing line cleanedin-place. It has been documented that even though lower-frequency in sonication is remarkably more efficient than higher frequency for reducing biofilm cells' viability, bacteria in food industries cannot be eliminated solely using the present ultrasonic technologies, thus ultrasound techniques are combined with other treatment techniques (ethylene-diaminetetra-acetic acid, enzymes or ozonation) have been recommended [START_REF] Baumann | Removal of Listeria monocytogenes biofilms from stainless steel by use of ultrasound and ozone[END_REF]).

The sustainability of these combined techniques has yet to be proven, but should be considered in a global strategy.

Cleaning operations in food industries require great quantities of drinking water, inducing environmental impacts today considered to be inacceptable. The dairy industry is for instance, consumes large quantities of water for food processing. Depending on the final product (milk, cheese, yogurt or milk powder), water consumption can go from 0.6L to as high as 6L per litre of raw milk treated (EDA, 2002). These figures make the dairy sector the highest water-consuming process per unit of raw material in the food sector. Apart from the production of the raw product (cattle breeding for milk production), most of the water consumption is imputable to food processing, which significant quantities required for cleaning operations.

One strategy to reduce the amount of water used, could be to clean with diphasic flows e.g. air and water. Too few works deal with this topic and to our knowledge, with the removal of microorganisms. However, [START_REF] Kondjoyan | Capillary force required to detach micron-sized particles from solid surfaces-Validation with bubbles circulating in water and 2 mm-diameter latex sphere[END_REF] demonstrated the interest of bubbles circulating in water generating a capillary force strong enough to detach micronsized particles from solid surfaces. Such micron particles could be considered as "model bacteria". Another option would be the use of foam. Hence, although foam cleaning, followed by rinsing operations, is widely used for open surfaces in the food sector, it has rarely been used for closed system cleaning. Indeed, foam flows are known to generate parietal shear stresses at least 100 Pa higher than in the case of liquid flow under identical flow rates. A recent study by Chovet (2015) demonstrated the potency of horizontal foam flow in pipes in the generation of high wall shear rate conditions using small amounts of surfactants and of water (void fraction over 80%). Preliminary data have recently been

Comment citer ce document : Faille, C., Cunault, C., Dubois, T., Bénézech, T. (Auteur de correspondance) (2018). Hygienic design of food processing lines to mitigate the risk of bacterial food contamination with respect to environmental concerns. Innovative Food Science and Emerging Technologies, 46 (SI), 65-73.

, DOI : 10.1016/j.ifset.2017.10.002

A C C E P T E D M A N U S C R I P T 17
proposed showing the interest of foam flow for the removal of Bacillus subtilis spores (Figure 6).

In addition, the soil generated by cleaning in place solutions induces large economic and environmental costs. Hence, recycling such solutions appears as an attractive alternative to reduce these costs. [START_REF] Blel | Effect of a new regeneration process by adsorption-coagulation and flocculation on the physicochemical properties and the detergent efficiency of regenerated cleaning solutions[END_REF] have proposed a cleaning solution regeneration technique using Na-bentonite and combining adsorption/coagulation and flocculation. The cleanability of stainless steel surfaces showed that regenerated solutions allow better surface wettability, thereby explaining the observed improvement in the cleaning of stainless steel surfaces including microbial soiling by B. subtilis spores.

Conclusion

In surface contamination, material surface properties roles, mechanisms induced by environmental conditions during soiling or cleaning lead to new proposals for the future as described above. It can be also mentioned that novel surface coatings and alternative chemicals for cleaning are being actively researched at an academic scale. A recent study by [START_REF] Moreira | Evaluation of SICAN performance for biofouling mitigation in the food industry[END_REF] proposed the use of surface alteration of stainless steel. They observed that after performing a cleaning protocol with chlorine, a reduction of bacterial counts was much higher on a stainless steel modified by the incorporation of silicon (a-C:H:Si or SICAN) compared to stainless steel. However, the interest of these new surfaces demonstrated at the laboratory level could be jeopardized by the surface conditioning after several soiling and cleaning cycles, which may potentially radically change their surface properties. Any improvement should be balanced with research approaches integrating industrial condition particularities. A way of attenuating this obstacle would be to favour milder cleaning conditions. This could be envisaged using more hygienically-designed production systems in combination with less aggressive cleaning substances. For instance, [START_REF] Lequette | Using enzymes to remove biofilms of bacterial isolates sampled in the food-industry[END_REF] demonstrated the interest of enzymes in the efficient removal of biofilms working with a panel of bacteria isolated from different food industry sectors. However, the longevity of surface coatings and the traceability of enzymes from closed systems remain to be fully demonstrated.

While maintaining high hygiene standards any option proposed to lower energy, chemicals or water used are currently much sought-after. As described in this paper, new 50 μm 2 superhydrophilic squares on a superhydrophobic surface) after incubation in a Bacillus spore suspension [START_REF] Galopin | Selective adhesion of Bacillus cereus spores on heterogeneously wetted silicon nanowires[END_REF].

Figure captions

Vieira

  et al. (1993) had already shown the impact of turbulences respectively on the biofilm macro-structures and microstructures. Under too high wall shear stress conditions(Tsai, 2005) observed a dramatic reduction in the surface microbial load at the stationary phase of the biofilm growth. All of these activities were done at the laboratory scale. Indeed, few works have looked into what happens in complex food equipment or processing lines. Quite recently[START_REF] Blel | Cleanability study of complex geometries: Interaction between Bacillus cereus spores and the different flow eddies scales[END_REF] worked on the soiling of an industrial two-way valve by a suspension of Bacillus cereus spores in water. The authors reaffirmed that in turbulent flow conditions, the transport process of particles is mainly governed by convection and diffusion. Comment citer ce document : Faille, C., Cunault, C., Dubois, T., Bénézech, T. (Auteur de correspondance) (2018). Hygienic design of food processing lines to mitigate the risk of bacterial food contamination with respect to environmental concerns. Innovative Food Science and Emerging Technologies, 46 (SI), 65-73. , DOI : 10.1016/j.ifset.2017.10.002A C C E P T E D M A N U S C R I P T 9 However, when viscous forces near the wall are high enough, the transport mechanism is mainly carried out by diffusion throughout the boundary layer. The adhesion process occurs due to attraction forces (van der Walls and electrostatic forces) between particles and the wall. Moreover, for bacterial spores of approximately 1 m width and 2 m long, adhesion forces are complex due to their surface energies and the potential presence of specific 3D surface structures. Indeed, in addition to the hydrophobicity and the relative charge of the surface which induce high attraction forces, B. cereus spores are surrounded by an exosporium thereby increasing contact surfaces, as its appendages are also in contact with the steel surface. In addition Blel et al. (2010) demonstrated the highly significant role of confined zones in terms of hydrodynamics, in constituting huge deposit areas at Reynolds numbers as low as 3300. They interpreted the surface load observed as a result of two phenomena, (i) spore convection and adhesion when the applied wall shear stress is moderate, but sufficient to ensure the transport of spores to the wall and (ii) spore deposition in confined zones characterized by weak mixing and thus low shear stress forces, when the residence time for spores is sufficient. Very recently, Cunault et al. (2015) working with a set-up composed of a series of mock-ups mimicking the design of washing tanks widely used in fresh-cut food industries, have studied the growth dynamics of biofilms developed on internal surfaces under turbulent flow conditions. These vats were filled with water containing Pseudomonas fluorescens cells and agitated by a Rushton impeller inducing a turbulent flow regime. The flow pattern inside the vats was highly modified by the design of the vats (corners, folds or flat surfaces). The authors demonstrated a strong link between the flow pattern induced by the design and the biofilm development dynamics. Using CFD, ranking of the different zones was based on the contamination load. The differences observed were compared to the flow arrangement inside the vats and to the CFD evaluation of the wall shear stress. Recirculation areas impact on the contamination load was emphasized by low wall shear stress conditions, such as in corners inducing high levels of attached bacteria over 10 7 CFU cm -² after 72h. Conversely for flat and vertical walls affected by the highest mean wall shear stress values, 10 times more, the observed surface contamination load was lower at less than 10² CFU cm -² after 72h. As in Blel et al. (2010), the wall shear stress parameter appeared to be insufficient to explain this difference. PIV (Particle image velocimetry) measurements have shown that fluctuations in the local flow velocity occurred directly due to the impeller blade rotation. Comment citer ce document : Faille, C., Cunault, C., Dubois, T., Bénézech, T. (Auteur de correspondance) (2018). Hygienic design of food processing lines to mitigate the risk of bacterial food contamination with respect to environmental concerns. Innovative Food Science and Emerging Technologies, 46 (SI), 65-73. , DOI : 10.1016/j.ifset.2017.10.002 A C C E P T E D M A N U S C R I P T 10 Such fluctuations over time, which has been shown to be a key factor to understand the surface contamination removal

  [START_REF] Jensen | Local wall shear stress variations predicted by computational fluid dynamics for hygienic design[END_REF] and[START_REF] Lelièvre | Hygienic design: influence of the local wall shear stress variations on the cleanability of a three-way valve[END_REF] demonstrated that wall shear stress alone is not sufficient to explain the level of removal of bacterial contamination from a surface. Indeed, in turbulent flow regimes, the fluctuation of this parameter would explain some of the discrepancies observed, such as high cleanability levels combined with low mean wall shear stress values.[START_REF] Blel | Effect of flow arrangement on the removal of Bacillus spores from stainless steel equipment surfaces during a Cleaning In Place procedure[END_REF] working on the cleaning efficiency of specific pipe features widely encountered in food processing lines arrangements, such as sudden or gradual contraction or expansion pipes and bends with various curved edges, have measured the local wall shear stress in parallel to the velocity profile to better understand how the flow arrangement could affect the bacterial removal through cleaning. They confirmed previous observations and highlighted the significant role of the flow dynamics induced by the geometry e.g. recirculation areas, high wall shear stress fluctuations, and how such flow perturbations could be transmitted along the line to deeply change the cleaning efficiency downstream. Despite the number of studies dealing with turbulence generation and transport near the wall, few authors have been interested in adhesion and detachment mechanisms of bacterial cells in the confined area near wall zones. Braaten et al. (1988) however, mentioned detachment under a turbulent flow regime of Lycopodium spores with an average diameter 10 times larger than the bacteria. Generally, the size and the density of particles are considered as major parameters, which control the kind of interaction with Comment citer ce document : Faille, C., Cunault, C., Dubois, T., Bénézech, T. (Auteur de correspondance) (2018). Hygienic design of food processing lines to mitigate the risk of bacterial food contamination with respect to environmental concerns. Innovative Food Science and Emerging Technologies, 46 (SI), 65-73. , DOI : 10.1016/j.ifset.2017.10.002 A C C E P T E D M A N U S C R I P T 11 coherent structures as equipment walls. According to Ziskind et al. (2000), particles high enough to reach the external region of the boundary layer, are subjected to the effect of the large scale motions in the external region contrarily to small particle dimensions probably located deeper in the viscous sub-layer, where the instantaneous velocity distribution is linear, as in the case of bacteria spores or initial biofilm stages composed of few cells directly attached to the surface or in small, flat clusters. In this zone, the effect of the large scale motion on particle re-suspension is excluded. Nevertheless, Corino and Brodkey (1969) showed that ejections and sweeps of coherent structures contribute to the increase in the wall shear stress. Ziskind et al. (2000) reported that horseshoe or hairpin vortices are the most important flow patterns inducing the detachment of small particles from the wall due to their contribution to the shear stress forces generated. Thus, whatever the size of the particles, eddies generated near the wall induce fluctuating shear forces. When these hydrodynamic forces are greater than the adhesion ones, re-suspension occurs. In Blel et al. (2007) B. cereus spore transport, adhesion and detachment mechanisms from a stainless steel wall during cleaning were discussed. Some fundamental concepts, such as the key characteristics of a turbulent flow near the wall and the nature of interaction between turbulence and an individual bacteria spore under simplified conditions, are used in order to explain residual levels of contamination of surface equipment after a CIP procedure. Briefly, the comparison between turbulent eddies' size and repartition and the dimension of B. cereus spores suggest the possible re-deposition phenomenon at zones characterized by high dissipation of the turbulent energy. This eventuality is also closely related to spore morphology and to the relative density between the fluid and the suspended spores. The work of Le Gentil et al. (2010) demonstrated this deposition phenomenon of contaminants even during CIP procedures. Experiments were focused on the surface contamination during the CIP procedure of pipes and of a two-way valve (cleaned and disinfected before the test) coming from soiled pipes (around 5 10 6 CFU cm -2 ) inserted in a clean loop. The authors observed that re-adhesion was controlled by the flow pattern, the valve being significantly contaminated after CIP. It is clear that equipment design plays a significant role in contamination trapping (Blel et al., 2010), but as shown here by Le Gentil et al. (2010), potential new cleaning in place strategies should take this phenomenon into account. More recently, Faille et al. (2013) have evaluated the respective roles of mechanical and chemical effects on the removal of Bacillus spores during cleaning-in-place. The authors Comment citer ce document : Faille, C., Cunault, C., Dubois, T., Bénézech, T. (Auteur de correspondance) (2018). Hygienic design of food processing lines to mitigate the risk of bacterial food contamination with respect to environmental concerns. Innovative Food Science and Emerging Technologies, 46 (SI), 65-73. , DOI : 10.1016/j.ifset.2017.10.002 A C C E P T E D M A N U S C R I P T 12 demonstrated that the mechanical action alone, such as the one delivered during standard industrial CIP conditions is not sufficient to remove any Bacillus strains. Hence, a CIP at 4 Pa (mean wall shear stress) in pipes appeared to be as efficient as a rinsing at 500 Pa. Spores from most of the species tested were shown by electron microscopy to be slightly affected by the chemical and temperature CIP conditions. The detachment efficacy during CIP is probably largely influenced by the spore's outer layer's susceptibility to chemicals, which may lead to the weakening with time of the interaction strength between spores and substrata. Hence along with the cleaning time, the removal kinetics of bacterial surface contamination has to be established in order to highlight such phenomena. Removal kinetics of B. cereus biofilms (Sylla et al., 2011) were modelled by a simple two-phase model

  energy factors: mechanical energy due to hydrodynamics for soil detachment, chemical energy breaking down soil and rendering them easier to remove, thermal energy which increases the effects of the two first factors and the cleaning time. It is commonplace to state that a restriction in one energy source may be compensated for, by increasing energy from the other factors. Nevertheless, a better understanding of cleaning mechanisms and of their dynamics is still needed not only to improve hygiene, but to take into account the impacts of such operations on the sustainability of food process industries. This would drive research toward a complete renewal of cleaning condition proposals.

  using the non-intrusive electrochemical method in straight pipes, Comment citer ce document : Faille, C., Cunault, C., Dubois, T., Bénézech, T. (Auteur de correspondance) (2018). Hygienic design of food processing lines to mitigate the risk of bacterial food contamination with respect to environmental concerns. Innovative Food Science and Emerging Technologies, 46 (SI), 65-73. , DOI : 10.1016/j.ifset.2017.10.002 A C C E P T E D M A N U S C R I P T 15 showed that the pulsating flows induced an increase in the local velocity gradient at the wall pipe. This result was explained by the periodic renewal of the boundary layers. Spectral analysis showed strongly increasing rates of the fluctuation energy for the different pulsating conditions in comparison with a steady flow. The test conditions involving a recirculation flow inducing a modification in the energy dissipation cascade, which can be explained by the redistribution of eddy size near the wall. In Blel et al. (2009b), experimental data on the removal of bacteria spores from pipe surfaces showed the contribution of the different pulsation parameters in the removal of adhered bacterial spores, in addition to the effect of the mean velocity of the flow. A high cleaning rate level is observed despite the reduction in the magnitude of the mean velocity. The role of the variation of the wall shear stress due to pulse conditions on bacteria removal efficiency should be investigated as a significant improvement observed in both spore removal rate and in the time necessary to reach a complete removal. More recently Blel et al (2013) working on a highly complex equipment, namely a scraped-surface heat exchanger soiled by biofilms of P. fluorescens, demonstrated again the interest of pulsed flow during CIP procedures in tough conditions. The study focused on the entry bowl of the exchanger, where three critical areas in terms of ease of cleaning were observed. This phenomenon was explained by the low mean wall shear stresses and low fluctuations measured under standard CIP flow conditions. The use of a pulsating flow completely modified the flow and thereby significantly reduced the residual contamination in those areas. Recently Foeste et al. (2013) has developed a CFD model based on the assumption of a mass transfer controlled cleaning process. A validation of the cleaning mechanism, using experimental data of local cleaning times in several complex geometries with varied static and transient flow velocities, was carried out. The authors stated that based on the new CFD model presented the local cleaning efficiency can be predicted, including any particular specificities of the pulsed flow conditions. Pulsed flow increases instantaneous rates of heat, mass and momentum transfer, equivalent to the use of much larger steady flow velocities and larger volumes of liquid. Less liquid can be used, cleaning carried out more quickly and more reliably, as a result of relatively cheap hydraulic energy input and pulsing equipment. Further research is still needed in this area for further industrial implementations. Srey et al. (2013) in a quite recent review of biofilms in food industries, mentioned ultrasonication, a well-known technique, as Comment citer ce document : Faille, C., Cunault, C., Dubois, T., Bénézech, T. (Auteur de correspondance) (2018). Hygienic design of food processing lines to mitigate the risk of bacterial food contamination with respect to environmental concerns. Innovative Food Science and Emerging Technologies, 46 (SI), 65-73. , DOI : 10.1016/j.ifset.2017.10.002 A C C E P T E D M A N U S C R I P T 16

Figure 1 :

 1 Figure 1: Observation by scanning electron microscopy of a patterned silicon nanowire surface (50 x

Figure 2 :Figure 3 .

 23 Figure 2: Observation by scanning electron microscopy of a biofilm formed by Kocuria varians and mainly located in surface defaults (PIHM)

Figure 4 :Figure 5 :

 45 Figure 4: Observation by scanning electron microscopy of a biofilm formed by P. fluorescens in a fresh-cut food processing equipment on fully-immersed areas [WET] and at the interface between air and liquid [DRY] (Cunault et al., 2015)

Figure 6 .

 6 Figure 6. Examples of removal kinetics of Bacillus subtilis spores at a mean wall shear stress of 5 Pa, SDS 0.3 % w/w under flowing foam cleaning conditions at 3 l h -1 (diamond captions)or liquid flow conditions at 300 l h -1 (rectangle captions)

  Fig 1.

  Comment citer ce document : Faille, C., Cunault, C., Dubois, T., Bénézech, T. (Auteur de correspondance) (2018). Hygienic design of food processing lines to mitigate the risk of bacterial food contamination with respect to environmental concerns. Innovative Food Science and Emerging Technologies, 46 (SI), 65-73.Comment citer ce document : Faille, C., Cunault, C., Dubois, T., Bénézech, T. (Auteur de correspondance) (2018). Hygienic design of food processing lines to mitigate the risk of bacterial food contamination with respect to environmental concerns. Innovative Food Science and Emerging Technologies, 46 (SI), 65-73.

	proposals for materials and equipment design combined with mild alternate cleaning
	conditions, minimizing water load and all environmental impacts of cleaning operations will
	become mandatory, if food industries are able to meet future challenges while preserving
	our environment.
	M A N U S C R I P T M A N U S C R I P T
	A C C E P T E D A C C E P T E D
	18 19
	, DOI : 10.1016/j.ifset.2017.10.002 , DOI : 10.1016/j.ifset.2017.10.002

  ). Hygienic design of food processing lines to mitigate the risk of bacterial food contamination with respect to environmental concerns. Innovative Food Science and Emerging Technologies, 46 (SI), 65-73. ., van der Mei, H. C., Gold, J., & Busscher, H. J.(2000). Retention of bacteria on a substratum surface with micro-patterned hydrophobicity. FEMS MicrobiologyLetters, 189(2), 311-315. Boulangé-Petermann, L., Gabet, C., & Baroux, B. (2006). On the respective effect of the surface energy and micro-geometry in the cleaning ability of bare and coated steels. Colloids and

	Sheng, X. X., Ting, Y. P., & Pehkonen, S. O. (2007). Force measurements of bacterial adhesion on metals using a cell probe atomic force microscope. Journal of Colloid and Interface Science, 310(2), 661-669. Somers, E. B., & Wong, A. C. L. (2004). Efficacy of two cleaning and sanitizing combinations on Listeria Bos, RSurfaces A: Physicochemical and Engineering Aspects, 272(1-2), 56-62. monocytogenes biofilms formed at low temperature on a variety of materials in the presence of
	Braaten, D.A., Shaw, R.H., & Paw, U.K.T. (1988). Coherent turbulent structures and particle ready-to-eat meat residue. Journal of Food Protection, 67(10), 2218-2229.
	detachment in boundary layer flows. Journal of Aerosol Science 19, 1183-1186. Srey, S., Jahid, I.K., & Ha, S-D. (2013). Biofilm formation in food industries: A food safety concern.
	M A N U S C R I P T Cerca, N., Pier, G. B., Vilanova, M., Oliveira, R., & Azeredo, J. (2005). Quantitative analysis of adhesion and biofilm formation on hydrophilic and hydrophobic surfaces of clinical isolates of Staphylococcus epidermidis. Research in Microbiology, 156(4), 506-514. Chovet, R. (2015). Experimental and numerical characterization of the rheological behaviour of a complex fluid: application to a wet foam flow through a horizontal straight duct with and without flow disruption devices (FDD). PhD thesis Valenciennes et du Hainaut-Cambrésis University. M A N U S C R I P T M A N U S C R I P T M A N U S C R I P T Food Control, 31, 572-585. Storgards, E., Simola, H., Sjoberg, A. M., & Wirtanen, G. (1999). Hygiene of gasket materials used in food processing equipment. Part 1: New materials. Food and Bioproducts Processing, Part C, 77, 137-145. Sylla, Y., Faille, C., & Bénézech, T. (2011) Removal kinetics of Bacillus cereus biofilms from food M A N U S C R I P T equipment cleaned in place, Proceedings of ICEF11, Athens.
	A C C E P T E D (2015). A novel set-up and a CFD approach to study the biofilm dynamics as a function of local flow conditions encountered in fresh-cut food processing equipments. Food and Bioproducts Processing, 93, 217-223. Díaz, C., Schilardi, P. L., Salvarezza, R. C., & De Mele, M. F. L. (2007). Nano/microscale order affects the early stages of biofilm formation on metal surfaces. Langmuir, 23(22), 11206-11210. EDA (European Dairy Association) Position paper (2002). Elvers, K. T., Peters, A. C., & Griffith, C. J. (1999). Development of biofilms and control of biofilm in the food industry, in Wimpenny, J., Gilbert, P., Walker, J., Brading, M. and Bayston, R. (eds). Biofilms: the Good, the Bad, the Ugly, 139-145. A C C E P T E D A C C E P T E D A C C E P T E D A C C E P T E D
	Faille, C., Bénézech, T., Blel, W., Ronse, A., Ronse, G., Clarisse, M., & Slomianny, C. (2013). Role of
	mechanical vs. chemical action in the removal of adherent Bacillus spores during CIP
	procedures. Food Microbiology, 33, 149-57.
	Faille, C., Bihi, I., Ronse, A., Ronse, G., Baudoin, M., & Zoueshtiagh, F. (2016). Increased resistance to
	21 25
	, DOI : 10.1016/j.ifset.2017.10.002 002 002 002 002

Cloete, T.E.,

Westaard, D., & Van Vuuren, S.J. (2003)

. Dynamic response of biofilm to pipe surface and fluid velocity. Water

Science and Technology, 47(5)

, 57-59. Corino, E.R., & Brodkey, R.S. (1969) A visual investigation of the wall region in turbulent flow. Journal of Fluid Mechanics, 37, 1-30. Cunault, C., Faille, C., Bouvier, L., Foeste, H., Augustin, W., Scholl, S., Debreyne, P., & Benezech, T. detachment of adherent microspheres and Bacillus spores subjected to a drying step. Colloids and Surfaces, Part B, 143, 293-300.

Faille, C., Jullien, C., Fontaine, F., Bellon-Fontaine, M. N., Slomianny, C., & Bénézech, T. (2002).

Comment citer ce document : Faille, C., Cunault, C., Dubois, T., Bénézech, T. (Auteur de correspondance) (2018). Hygienic design of food processing lines to mitigate the risk of bacterial food contamination with respect to environmental concerns. Innovative Food Science and Emerging Technologies, 46 (SI), 65-73. , DOI : 10.1016/j.ifset.2017.10.Comment citer ce document : Faille, C., Cunault, C., Dubois, T., Bénézech, T. (Auteur de correspondance) (2018). Hygienic design of food processing lines to mitigate the risk of bacterial food contamination with respect to environmental concerns. Innovative Food Science and Emerging Technologies, 46 (SI), 65-73. , DOI : 10.1016/j.ifset.2017.10.Comment citer ce document : Faille, C., Cunault, C., Dubois, T., Bénézech, T. (Auteur de correspondance) (2018). Hygienic design of food processing lines to mitigate the risk of bacterial food contamination with respect to environmental concerns. Innovative Food Science and Emerging Technologies, 46 (SI), 65-73. , DOI : 10.1016/j.ifset.2017.10.Comment citer ce document : Faille, C., Cunault, C., Dubois, T., Bénézech, T. (Auteur de correspondance) (2018). Hygienic design of food processing lines to mitigate the risk of bacterial food contamination with respect to environmental concerns. Innovative Food Science and Emerging Technologies, 46 (SI), 65-73. , DOI : 10.1016/j.ifset.2017.10.Tang, H., Cao, T., Liang, X., Wang, A., Salley, S. O., McAllister, J., & Ng, K. Y. S. (2009). Influence of silicone surface roughness and hydrophobicity on adhesion and colonization of Staphylococcus


Gilles Garel
email: garel@mlv-univ.fr

Christophe Midler
email: .midler@poly.polytechnique.fr

Mars

Front-Loading Problem-Solving in Co-Development: Managing the Contractual, Organisational and Cognitive dimensions 1

Keywords: concurrent engineering, co-development, contracts, learning, die design construction, electronics, chemistry, pharmaceutics

Front-loading " problem-solving is one of the major strategies to reduce development costs and development lead time. In co-development situations, the implementation of such methodologies rises specific questions, due to the difficult partition in responsabilities and skills between the car manufacturer and the supplier, especially when customer and supplier contributions cannot be clearly interfaced in a " black-box sourcing " relation.

This results in a difficult and permanent debate about design modifications.

The article analyses such a co-development situation in the case of a car manufacturer and its die design and engineering suppliers. The case illustrate how to combine organizational integration (i.e. co-localization, shared development methodologies) with new economic contracting rules which create front-loading problem-solving incentives for the two partners. We compare the economic outcomes of a traditional process with a co-developped project, from the viewpoint of both the customer and the suppliers.

The study demonstrates how co-development played a major role in reducing the number and cost of modifications for the customer. The benefits which suppliers can earn depend on their ability to involve in the project in terms of design and engineering capacity at an early stage. These results generate theoretical outputs which bridge the gap between incentive and contract theories on one side, and cognitive and learning fields on the other.

Introduction

" Front-loading " problem-solving [START_REF] Thomke | The Effect of 'Front-Loading' Problem-Solving on Product Development Performance[END_REF] is one of the major strategies to reduce development costs and development lead time (Midler, 1995, p 369). In co-development situations, the implementation of such methodologies rises specific questions, due to the difficult partitions in responsabilities and skills between the car manufacturer and the supplier. The problem is particularly important when customer and supplier contributions cannot be clearly interfaced in a " black-box sourcing " relation. The result is a difficult and permanent debate about design modifications.

The article analyses such a co-development situation in the case of a car manufacturer and its die design and engineering suppliers. For the car manufacturer, the target is to reduce the number of dies modifications number and thereby the budget, which has a major impact on the global performance of the projects. But on the other side, in the traditional relationship, modifications appear for the supplier as a important complementary revenue. Therefore, the codevelopment efficiency depends on the capacity to combine organisational integration (i.e. co-localization, communication, ...) and adapted shared frontloading methodologies with new economic contracting rules which create frontloading problem-solving incentives for the two partners. This article analyses a case experimenting such a combination of new organizational and contracting co-development practices. It is based on interactive research conducted with an European auto-maker, and of a representative sample of the company's stamping-tool suppliers [START_REF] Garel | Analyse d'un codéveloppement[END_REF]. Following the outsourcing of stamping operations in the early 1990s, this auto-maker, which we will refer to as "X," wished to evaluate its new partnerships with suppliers. In the context of a study conducted over a period of two years, we were able to cross-analyse the viewpoints of both the customer and its suppliers. In order to assess the profits and losses generated by co-development, we did a comparative study of two successive automotive projects: a TR (Traditional) project, conducted without co-development from the late 1980s to the early 1990s, and the following 4 , a CD (Co-Development) project, pioneered jointly with the toolmakers in the early-mid 1990s. We analysed the performance of four European tool-makers (A, B, C, D) participating in both the TR and CD projects. The field study was conducted from December 1995 to July 1997. We drew on internal data collected from Auto-Maker X and its suppliers (files, reports, notes, etc.); on reassessments made at our request (submitted by the firms); on interviews (over thirty); and on regular cross-checking carried out by the steering committee of the interactive research.

In the first part of this article, we will analyse the differences in the two studied development processes, by refering to our characterization of the co-development concept. In the second, we present our comparison of co-development performance with traditional design process one. The research was targeted on the development and investment costs. An important characteristic of our methodology is that it reflected not only the car manufacturers viewpoint, but also the suppliers economic vision (the methodology was validated both by the automaker and the suppliers). We present the results of this analysis in section 2 .2.

As will become apparent, these results substantiate the hypothesis of a "win-win" situation between customer and supplier, although not all suppliers reaped the same benefits. In the third and final section, we discuss our results through an analysis of the advantages accruing from co-development in terms of two variables: supplier engineering skills; and long-term stability of the automaker/supplier relationship. This analysis supports the need for systematic 6 integration into the theoretical design-performance model of organizational, incentive and cognitive factors.

Comparison of TR and CD processes on organizational and contract variables.

Many authors have contributed to define the partnership and co-development notions. Consistently with those of those [START_REF] Lamming | Beyond Partnership: Strategies for Innovation and Lean Supply[END_REF] and [START_REF] Liker | Engineered in Japan, Japanese Technology Management Practices[END_REF], we will characterize co-development processes in terms of five conditioning factors [START_REF] Midler | Le co-développement: définition, enjeux et problèmes[END_REF]. The idea being that codevelopment efficiency is the result of a global coherency of this set of variables.

-The early selection of a supplier, based on strategic criteria, for a cooperative endeavor lasting throughout the duration of the development process.

The die tools development includes two phases (see figure 1): phase 1 is a design period and ends in a technical specification freeze of the tool. Phase two is a production period of the tools. For project TR, Phase 1 lasted for 4 months, compared to 18 months for Project CD. Phase 2, on the contrary, was shorter for Project CD. It has been further extended for more recent projects5 .

For CD Project, the customer-supplier relationship was formed at the beginning of phase one, the selection being made on the basis of positive previous experience with the suppliers, and on the customer's long-term strategic objectives. For TR project, this relationship was established only after the technical definition of the new product had been completed, at the end of phase 1, on the result of the cost bidding process. -Supplier involvement affecting a broader operational perimeter.

Co-development implies a shift from basic-component supply to transactions involving complete vehicle sub-systems. In the metal-stamping field, assignments to tool-makers are today made by the total lot, and are based on the physical perimeters defining an entire system (for example, all the stamped pieces for a door); whereas, formerly, assignments were made component-by-component and awarded to the lowest bidder. This way, interface problems between individual components (the geometric fit and visual appeal of the body as a whole) are all handled by the same supplier. Figure 2 gives the difference between TR and CD projects concerning components in a lot assigned to major supplier. A design process inevitably implies unforeseen problems and modifications not included in the original specifications. The skills which need to be mobilized for a design operation are hard to define and coordinate [START_REF] Schön | The Reflective Practitioner, How Professionals Think in Action[END_REF][START_REF] Nonaka | A Dynamic Theory of Organizational Knowledge-Creation[END_REF].

It is therefore more important to learn quickly together than to initially agree on a detailled (but rapidly obsolete) definition of the future product. In this perspective, the agreement between two firms must be consistent in terms of joint work procedures and the means for dealing with unexpected problems or revised objectives.

The comparison of TR and CD project is typical of such a transition. In TR project, the machine tools suppliers did not participate in the design phase.

Consensus was reached on a basis of theoretical initial technical specifications that had not been validated by those (the suppliers) who were supposed to implement them. In CD project on the contrary, the machine tool suppliers were involved in the colocated project through residential engineers from the beginning of the design. Common methodologies were negociated to identify problems quickly, to jointly formulate possible solutions, evaluate their economic impact, implement them, and finally optimize the elimination of decision-making inertia when effecting the required modifications. Those methodologies implied development of mock up, problem solving data base, sharing of the CAD specifications… During the course of the project, the proposals made by the various players in the design process were open for discussion and revision.

Typically, suppliers were supposed to alert and ask for design changes when they anticipated feasability problems. They were supposed to adopt such a proactive alerting role, as opposed to a passive reaction to customer inspections.

-The supplier's commitment to an overall result, measured in terms of quality, cost, and time.

In co-development, the supplier's commitment covers the total design / testing / production / delivery process. The customer must be certain that the supplier will use its significant margin of manoeuvre to carry out the co-development project in the direction initially planned.

Due to this principle, the initial contract in project CD fixes globally the remuneration with special clauses dealing with modifications, as described in the following §. The shift to co-development transforms negotiated pricing into effective remuneration for suppliers; whereas budget overruns were usual under the traditional system.

-The integration of economic and technical imperatives : the contracting rules about modifications

In traditional projects the economic relation is ruled between purchasing and commercial agents who are largely cut off from the engineering arena of manufacturer and supplier. The dissociation is also temporal : first there are the technical decisions within the auto-maker, then the bidding and the economic negotiation, then the technical achievement, and lastly, the negotiation about the modifications. Under co-development, economic negotiation becomes a process of building value through the design process (during which technical variants are costed, the effects of modifications evaluated, etc.). Suppliers' remuneration is the result of specific achievement benchmarks, rather than solely made on the basis of accounting considerations formulated by the customer's purchasing department.

The contracting rules about design modification experimented on the CD project is typical in that perspective. Modifications are a classical problem in the auto industry. They can vary in importance: from the shift of an opening on a component, to a change in the overall style of the product. Budget overruns caused by modifications could previously reach 20% to 30% in the studied firm on a given project. For the auto-maker, a major advantage of the shift to codevelopment is that modifications tend to be reduced in number. Modifications carried out during Phase 2 are the most costly. To embark on Phase 2 is to embark on the stage of project irreversibility, or project reversibility only at an extremely high cost. Tardy discovery of the need for modifications involves heavy additional costs, since at this stage, the modifications must be made on the finished tools rather than on the preliminary designs. In other words, modifications can be very valuable during Phase 1, but are extremely costly during Phase 2.

Under the sub-contracting system, each modification becomes the subject of an amendment to the initial contract. Suppliers are free to negotiate a low initial price, since they know they will have an opportunity to "hike it up" during the life of the project. In order to persuade suppliers to play the game of early modification identification, the co-development contract includes (importantly) a clause specifying that no additional costs will be paid for late identification of the need for modifications. A comparison between the traditional and the codevelopment systems is quite illuminating in this regard. Under the sub-contracting system, Auto-Maker X is wholly responsible for modifications. In Phase 1, since suppliers do not participate in the design phase of the project under this system, modifications cannot originate with suppliers.

During Phase 2, if the tool-makers suggest modifications, Auto-Maker X must pay the costs, since he bears sole responsibility for the design. style changes, modifications in the safety system, etc.). This compensation, which reflects an improvement in tool design, leads to a reduction in tool costs (e.g.:

reduction in the number of tools per vehicle-model from five to three). This clause motivates suppliers to provide any expertise not possessed by the auto-maker at the earliest possible opportunity. The converse of this argument runs as follows: if the auto-maker were to pay for all the modifications originating with it, toolmakers would not be motivated to compensate for them and would thus become less involved in the planning stages.6 This incentive system has already been observed at firm J by [START_REF] Aoki | Sur certains aspects des conventions dans l'entreprise[END_REF], who maintains that the more auto-makers protect sub-contractors from risk, i.e. the more responsibility auto-makers assume for cost overruns resulting from modifications, the less incentive suppliers will have to pursue innovation on their own.

(2) When suppliers pay the costs for Phase 1 modifications, they are encouraged to propose only those improvements that will result in lower tool costs. This is because, when suppliers lower the cost for tools during Phase 1, they improve their own profit margin, since they are contractually guaranteed payment at the price fixed during initial negotiation. Improvements originating with suppliers "go straight into the suppliers' own pockets".

(3) Auto-makers have an incentive to identify themselves needed modifications during Phase 1, since they will have to pay unanticipated modifications during Phase 2 themselves. This is the only exception to the fixed-price nature of the contract.

(4) When assuming total responsibility for tool design under co-development systems, suppliers pay the costs for all modifications originating with them. The high cost of Phase 2 modifications, acts as an incentive for identifying the need for modifications during Phase 1.

To sum up: since all Phase 2 modifications represent increased costs for the party identifying the need for them, this acts as an incentive for early identification.

During Phase 1, suppliers are motivated to reduce the costs of the tools for which they are responsible by improving their design.

EVALUATION OF CO-DEVELOPMENT COST PERFORMANCE

Methodology.

Our study is comparative, evaluating the respective results of two projects: one carried out according to the traditional sub-contracting approach (TR project), and the other according to the conditioning factors described above (CD project). Our approach is differential: we have measured the performance differentials between TR and CD projects. Hypothetically, the profit/loss differential observed between the two projects can be attributed to the shift (in one case) to the co-development method. Both projects studied were very similar in terms of vehicle-model, year of launching (less than two years of difference); also economic assessments were made in constant French francs (base: year of TR project). Furthermore, the basis of comparison for aggregating data was the same.

Our comparison is based on the analysis of three cost indicators: the estimated cost, the negotiated price and the value of modifications.

-In order to evaluate Phase 1 performance, we measured, for all tools on Projects TR and CD, the differential between tool cost at the beginning of Phase 1 (or estimated cost) and cost of the same tools at the conclusion of Phase 1. The first cost corresponds to the initial technical evaluation of the tools. We call this "estimated cost," and it serves as the basis for all of our measurements. Initial specifications for the tools are provided by the systems-engineers of Auto-Maker X: the customer knows how to specify the type of tools it wants to receive from the supplier. The same method of calculation-a widely recognized one, employed by suppliers-was used to determine the two costs on both projects.

Calculations that do not appear were made for research purposes by the methods department at Auto-Maker X.

-In order to evaluate the impact of co-development on the auto-maker-supplier negociation, we have measured the differentials between estimated tool costs and costs negotiated with suppliers for TR and CD Projects.

-Finally, we have measured the value of Phase 2 modifications as a percentage of estimated tool costs for TR and CD projects.

The above indicators could be documented with the auto-makers data. The access to suppliers data was more difficult. These suppliers were competing with each other and were conducting negotiations with Auto-Maker X at the time of the research. The problems were solved due to both the credibility previously established by the field researcher [START_REF] Garel | Réduction du temps de conception, concourance et savoirs professionnels: le cas de l'emboutissage dans les projets automobiles[END_REF], and to lengthy discussions undertaken with each supplier. A questionnaire and survey agreement enabled each supplier to understand our study objectives, and to prepare for each of our visits. Our investigation sought to evaluate the effects of co-development on the strategy, organization, and resources (human, design, plant, etc.) of these firms;

and on the customer/supplier relationship from the viewpoint of the suppliers (commercial negotiation, contract signing, work at the planning stage, etc.). Two studies devoted to modifications for TR and CD projects and to the economic performances of these firms were also conducted.

Results of the co-development performance measurement

-A reduction in tool costs. Co-development generated a 7% reduction in tool costs at the end of Phase 1, whereas the traditional sub-contracting system posted a cost overrun of 11%. A tool-by-tool study shows that the reduction for the CD project reflects improvement in tool design during Phase 1, i.e. during participation of suppliers at the planning stage. For example, Supplier A succeeded in improving the process for one lot of tools under the CD project by reducing the number of tools from 12 to 4, representing a cost reduction of 48%.

By contrast, the TR project registered an increase in the complexity of the tooling process during Phase 1 due to problems with delivering pertinent expertise in a logical sequence during the planning stage, to the lack of an improvementincentive clause, and to the absence of the suppliers' own experts. We concluded that, under co-development, the Auto-Maker achieves savings equal to the cost overruns on the TR project (11%), and that suppliers will increase their profit margins if they can reduce tool costs (7%).

-An increase in the negotiated price. For the two partners, what effect does codevelopment have on the negotiated tool price? It is clear that under co-development the auto-maker pays more for tools during the initial negotiation, since the suppliers must anticipate modifications and profit margins during a single negotiation, with no hope of renegotiation. In fact, under the CD project, negotiated tool prices averaged at 23% higher than initial costing or cost estimates. Under the TR project, the differential was 16% (discrepancy = 7%, which is a benefit for the suppliers and a loss for the auto-maker). For suppliers, this differential measures the cost of future risks. Auto-Maker X did not, however, "push" the negotiation too hard for this initial co-development experiment under the CD project.

-A sharply reduced investment in modifications. The number of Phase 2 modifications was significantly reduced. They accounted for 49% of estimated tool cost under the TR project, compared to only 15% under the CD project (delta = 34%). In other words, investment in modifications under co-development were divided by almost 3.5, the result of a major reduction in modification volume.

This observation is unique in the history of the automotive industry. The 34% reduction of modifications cost is clearly a profit for the auto-maker. We agree with the suppliers in considering that the reduction in modifications constituted a net loss in revenues, compensated by advantages obtained in production management (plant-flow equalization during Phase 2 was much easier, and production-times were shortened), and by the possibility of doing other business (income-generating business) during the time-period freed by modification reduction. Therefore, as a working figure, we have entered 0.

The figure 5 presents these results as a profit-loss balance sheet for auto-maker and suppliers. There is a clear differential in these results: between profits and losses, between profit levels, between customer and suppliers, and among the various suppliers.

How can these be explained?

EARNING PROFITS FROM THE CO-DEVELOPMENT SITUATION

Co-development is advantageous to those suppliers capable of developing their design expertise on a long term.

Supplier expertise

Tool-maker profitability is heavily dependent on engineering expertise. We have noted and verified a strong positive correlation between supplier performance and supplier design-capacity as measured in a given supplier's (1) human resources [START_REF] Kay | Foundations of Corporate Success: How Business Strategies Add Value[END_REF][START_REF] Grant | The Resource-based Theory of Competitive Advantage: Implications for strategy formulation[END_REF] The Supplier B and D age-pyramids are relatively older than those of Suppliers A and C, a difference explained by the fact that design-department employees tend to be younger than those in other departments. It also reflects the considerable investment made by Suppliers A and C in a youthful and highly-qualified work force.8 These young recruits also reflect heavy technological investment in digitalization and simulation-investments9 enabling these suppliers to reduce design time and improve the management of unforeseen Phase 1 modifications.

Tool-Maker D has not developed a design department or planning facilities and, in the absence of a project team, this firm-small in size and European in scopecannot offer co-development expertise to its customers. Its design department has not been significantly modernized. Studies are not digital, and investments in CAD are low. Despite a large design staff in terms of percentage of total work force, Supplier D sub-contracts much of its design-study work. However, this sub-contracting is poorly handled and creates a dependency situation for the toolmaker in relation to his own design-study suppliers. 10 The lack of project structure has created coordination problems between customer and supplier.

Supplier D is the only one which did not reap any advantages from participation in Phase 1, and modification reduction was negligible. In contrast to the operations carried out with Suppliers A, B, and C, the auto-maker's engineers were forced to make trips during Phase 2 to the premises of tool-maker D more often under the CD project than under the TR project, in order to compensate for this lack of skills (Figure 8). Co-development revealed the structural weaknesses of this supplier. Tool-Maker A is positioned as a complete service-provider from the design of auto-body components to their final assembly. This supplier earned a substantial profit from co-development in the pre-production planning stage (profit of 35%).

The firm developed its digital design and R&D departments extensively, and five years ago implemented a "heavyweight" project structure [START_REF] Clark | Organizing and leading 'heavyweight' development teams[END_REF]. Within the firm, organization according to project is a factor which promotes consistency. The project structure "holds together" all the investments and reorganizations by linking them to one another within a coherent system. It is also an attempt to duplicate the auto-maker's own organization, thus facilitating the customer/supplier interface. Supplier C, like Supplier A, has been developing its engineering skills for many years.

The ability to earn profits from a co-development situation is thus strongly dependent on skills provided by the supplier. A skill-based approach puts the interpretation of performance in terms of incentives and design processes into perspective. Front-loading design processes and project collocalisation, even when associated with economic incentives are not in themselves sufficient to mobilize suppliers at the inception of a project. Although they positively affect both the early identification of required modifications and tool-cost reduction, profits are largely generated by tool-makers' skills, and not merely by these economic incentives. Shifting economic responsibility onto the shoulders of the tool-maker is not enough; the means through which the tool-maker can assume this responsibility must also be provided by developing new engineering capacities, through human and technical investment within the supplier on one hand, and through participation of successive projects with the auto-maker on the other hand.

The long-term stability of the co-development relationship

Skills acquisition and investment by suppliers implies the extension of the intercorporate relationship beyond a single project. Duration over time builds trust and develops learning. It also represents a guarantee of revenues, i.e. profit expectations are increased if the contract is renewed without subterfuge on either side. Suppliers will not undermine the interests of a customer that can guarantee steady revenues. Under the system of joint participation described by [START_REF] Imaï | Interpenetration of Organization and Market: Japan's firms and market in comparison with the US[END_REF], the two parties agree to renew their cooperative venture if each one has fulfilled its obligations. Game theory demonstrates that the duration of the relationship constitutes an incentive to cooperate. In a survey dealing with the American and Japanese car industries, [START_REF] Cusumano | Supplier relations and management: a survey of Japanese, Japanese-transplant, and US-auto plants[END_REF] note that the relationship between contractors and auto-makers lasts for over ten years.

Further, [START_REF] Donada | International Survey of Automotive Suppliers[END_REF] note that customer and supplier involvment in co-development relationships today lasts for an average of 23 years. Codevelopment is conceived as a game that is continuously replayed, but its total lifespan is determined by results. Although co-development reflects a strategic change for Auto-Maker X, and although it involves a longer-lasting relationship than the traditional one for design sub-contracting, the customer still does not guarantee the supplier that it will be systematically selected for each new development. Behind this uncertainty, suppliers perceive a contradiction between, on one side, a coherent and motivating proposition from the Auto-Maker X management on partnerships with suppliers; and, on the other, organized debate within the firm on the desirability of an alternate method ("what if, ultimately, selection of the lowest bidder turned out to be the least costly solution?"). This vacillation worries suppliers. Co-development-and the commitment to long-term organization and investment it involves-requires a degree of stability in the organizational choices made by each of the partners. "Our investment strategies are strongly dependent on the continuation of a sustained volume of stable operations in the future" (all suppliers). In today's context of drastic reduction in design costs by auto-makers, the pressure on suppliers at the time of negotiation is very strong. The cost factor, as a determinant in the selection of suppliers, is indeed an integral part of the inter-corporate cooperation system. The estimated/negotiated cost differential observed between TR and CD projects (+7%) is sharply reduced for projects after the initial CD project. This pressure on prices reduces revenues, affects supplier profit margins adversely, and over time raises the question of how long co-development can be sustained: "like other auto-makers, X requests a 20% reduction for each new project; the problem with a 20% reduction is how to maintain profit margins" (all suppliers).

Duration does not depend solely on the amount of time allowed by the customer for the co-development relationship. It is also a function of the co-development strategy of management and suppliers. What is the "strategic intention" [START_REF] Hamel | Strategic Intent[END_REF]) of these managers in terms of co-development? "Strategy" is understood in this context as the fit an organization achieves between its own resources/skills and the opportunities/risks created by its external environment [START_REF] Hofer | Strategy Formulation: Analytical Concepts[END_REF]. The formulation of medium-term strategy is the only way to give coherence to the investment and organizational choices implemented by suppliers in the context of co-development. The tool-makers' strategies are closely linked to the proportion of their revenues accounted for by Auto-Maker X.

As it happens, Auto-Maker X is a major customer for the suppliers we studied.

The only supplier-managers who failed to offer a strategic vision were those of Supplier D. They consider that the implementation of co-development is "unnatural" since firms are not intended to cooperate, but to organize their relationship via the market. This supplier's lack of project structure and investment in design skills reflects its lack of strategic perspective. By contrast, the investment of tens of millions of French francs in an ultra-modern plant, the development of engineering skills, the implementation of data systems, and the modernization of organizational systems at Supplier C reflect a strong strategic vision.

Conclusion

How to implement front-loading problem-solving strategies through codevelopment ? This article explored this question on the case of a relation between a auto-maker and its die-tools suppliers, a typical situation where product and process design are tightly associated in making the development performance.

Efficiency in frontloading strategies in co-development Our analysis showed that to be efficient in that perspective, the relations have to meet three kinds of conditions. On the organizational level, co-design and frontloading methodologies ; on the contractual level, incentives for upfront learning and problem solving ; on the cognitive level, engineering capacities and multiprojects cooperation learning. With this complex of conditions, co-development appears as a win-win situation, which is generally not the case if one of these conditions fails.

Figure 9: the determinant factors on codevelopment front-loading efficiency.

Our study, closely focussed on machine tools for the automotive industry, leaves some consequences of co-development unexamined. For example, we have not studied the effects of this new organizational method on development timeframes, a major factor in the competition between firms developing new products. The above table was drawn up for both the CD and TR projects. The data on tables 3 and 4 in the body of the article show the differentials between the results obtained for each one of the projects (double-framed box in the above table).

Figure

  Figure 1: Co-development and the extended supplier time involvement

Figure 2 :

 2 Figure 2 : comparison of component assignment to TR and CD suppliers.

Figure 3 :

 3 Figure 3: Payment of modification costs in sub-contracting system

Figure 4 :

 4 Figure 4: Payment of modification costs in co-development system

Figure

  Figure 5: Overall Co-Development Balance Sheet

Figure 8 :

 8 Figure 8: Number of monthly visits to suppliers by Auto-Maker X representative during Phase 2

  The development time-frame was shortened by over 10% between TR and CD projects, a tendency that accelerates with subsequent projects. Also unexamined are the effects of co-development on human-resource management (e.g.: stress and sometimes professional burn-out at the end of certain co-development projects; the effect on the relationship between project teams of coexisting but differing modes of customer relations practiced within the same firm)the calculation method, formulated ad hoc for our research purposes, used to arrive at the various differentials enabling us to measure co-development performance. With E1 = estimated cost, E2 = cost at end of Phase 1, E3 = negotiated price, E4 = cost of Phase detail by tool in lot E1......... and E1......... and E4......... .........E2.......... .........E3.......... ...................... diff. E1and E2 in % diff. E1 and E3 in % E4 in % of E1 total lot ∑E1......... and ∑E1......... and ∑E4......... .........∑E2....... .........∑E3....... ...................... diff. ∑E1 and ∑E2 in % diff. ∑E1 and ∑E3 in % ∑E4 in % of E1 total suppliers ∑(∑E1)..... and ∑(∑E1)..... and ∑(∑E4)..... .....∑(∑E2)....... .....∑(∑E3)....... ...................... diff. ∑(∑E2) and ∑(∑E1) = performance in Phase 1 diff. ∑(∑E1) and ∑(∑E3)

Adoption of joint development methodologies focused on front-loading and learning.

	Number of components	1	2	3	4	5	6	Mean
	assigned to major supplier /
	total number of components
	in the lot							(en %)
	Projet TR	3/5	8/50	4/7	6/23	10/12 5/14	46%
	Projet CD	5/5 23/32 7/7 12/12	6/8	8/12	85%
	-

Time to-market strategies focus on reduction of leadtime between specifications freeze and market introduction.

Suppliers can, however, contest the pertinence of a modification required by Auto-Maker X by referring it to a panel of peer assessors that meets at the conclusion of the project.

N.B. for reasons of confidentiality, we decided to express the data relative to Suppliers B, C, and D in a percentage of the base 100 corresponding to Supplier A, and to mask data on sub-contracting rates for design studies (average rate = approximately 50%).

It is nevertheless the most highly-qualified suppliers, and often those of longest-standing, who participated in the auto-maker's Phase 1 planning stage. It should also be noted that metal-stamping as a field has historically had a long tradition of apprenticeship.

For example, apart from training costs, a fully-equipped 3-D CAD workstation costs approximately FF 300,000.

The field covered by these design consultancies is industrial design in general and not machine-tools in particular. This non-specificity is reflected in the tardy identification of problems, since Supplier D does not possess the means for verifying all sub-contracted design work. Here we see that in order to sub-contract effectively, knowledge of how the job should be done must already be possessed internally. Tardy identification of errors creates tensions in the relationships between the design consultancy and the toolmaker's plant and are costly in terms of wasted time.