Thibaut Guyot Master Biologie-Gestion

Valérie Gagnaire
email: valerie.gagnaire@inra.frfanny.guyomarc-h@inra.fr

Fanny Guyomarc'

Properties of legumes, egg or milk products and new opportunities from mixes. Bibliographic synthesis in biology and biotechnology

Thanks also to the managers of the Master biology-management in the people of Mrs Marie-Andrée ESNAULT and Mrs Valérie GUILLAUME, for their advices in the writing of the bibliographic synthesis and in the follow-up of the project throughout the years 2018-2019.

« Le tuteur chercheur a pour rôle de conseiller l'étudiant, l'orienter dans ses recherches bibliographiques, l'aider à comprendre les articles, en faire une synthèse de manière logique et rigoureuse. Il ne peut vérifier toutes les citations et interprétations de l'étudiant. Il ne peut donc s'engager vis à vis d'éventuelles erreurs ».

Summary of tables and figures

 1: The behavior of pea proteins at the oil-water interface in a sequence of [START_REF] Altahir | Effect of partial substitution of soy milk on the chemical composition and organoleptic attributes of yoghurt[END_REF] migration, [START_REF] Amagliani | Globular plant protein aggregates for stabilization of food foams and emulsions[END_REF] adhesion, (3) partial denaturation and reorientation, and (4) formation of a viscoelastic film at the interface [START_REF] Burger | Recent progress in the utilization of pea protein as an emulsifier for food applications[END_REF]

I. Introduction

Since the advent of the consumerism in the last century, most of the western countries have achieved to create an efficient agriculture system in order to feed their ever-growing population. However, several regions of the world didn't reach this state, especially in the lower-middle income countries in Asia, Africa or South America. In an ever-growing human population, food security is a challenge that these countries need to address. In addition, it is well known that mass production of animal protein in western countries does have an impact on the environment. While trying to reduce their environmental footprint, the world richest countries also began to search for more eco-friendly foods.

Mixed foods are one of the multiple solutions that could respond to the requirement of reducing animal farming for environmental and health issues, with little impacts on western food habits. Furthermore, it can increase access to nutritionally balanced food in emerging countries. However, mixed foods are sparingly used to date. In France, the National Research Institute of Agronomy (INRA), works on government directives who calls in a new way to sustain the increase in the world population and the food demand. Among others, the egg and milk science and technology lab (STLO), Rennes, France is currently trying to design mixed foods that can combine both animal and vegetable products, in order to keep the benefits of an animal nutrient income while lowering the environmental, health and production costs by using nutritive and affordable plants. In that way, legumes like soy, pea, chickpea or lupine are subject to a growing interest. Thanks to their high protein content, evidence is growing that combining animal and plants products makes it possible to create a nutrient rich and affordable food with reduced environmental and health drawbacks.

Therefore, many researches have thought deemed necessary to understand the molecular interactions between the animal and vegetable systems. It is the first step that will allow recreating these complex molecular interactions. Gelation, for instance, implicates the formation of networks between reactive proteins to turn a solution into a solid, involving fermentation or not. By modulating the pH of the medium, it is actually possible to obtain different kind of gels [START_REF] Grygorczyk | Combined acid-and rennetinduced gelation of a mixed soya milk-cow's milk system[END_REF]. It also depends on the ratios between animal and plants products [START_REF] Park | Characteristics of yogurt-like products prepared from the combination of skim milk and soymilk containing saccharified-rice solution[END_REF], which have an impact on the rheological behavior of the mixes and on their sensory profile. This review presents a current state-of-knowledge on the researches made on food based on mixes of animal (egg or milk only) and plant (legumes only). First, we will establish a fine composition of all individual ingredients that are possibly used to make animal-plant based food, their physical and nutritional behavior. Then, several animal-plant mixes made under different operational conditions will be reviewed, in regards of the properties previously described, including the maximum possible combinations of ingredients. Since proteins are mainly involved in those physical behaviors, this review will focus mainly on these components, although other biomolecules like fats also have an impact on physical interactions. Some information about nutritional properties of the components will also be shown, in order to highlight the potential benefits of the mixes.

II. Nutritional composition and properties, and related rheological behavior of each ingredient of interest

A.

Composition and nutritional assets of animal and vegetal products selected

The ingredients targeted for the elaboration of the different mixes come from two different origins: plants and animals. We selected for this review two animal products: cow's milk and hen eggs. Both are widely part of the nowadays western human diet. The global production of cow's milk is about 827 million tons in 2018 (FAO 2018) while the global production of eggs approaches 80 million tons. We chose to select legumes as plant resources for this study. Legumes are plants from the family Fabaceae [START_REF] Turland | International Code of Nomenclature for algae, fungi, and plants[END_REF]). They include peas, soy, beans, lentils, lupine and other plants that constitute high source of vegetal proteins and are low in fat. In addition, they represent a source of other components, like complex carbohydrates (including fibres), phytosterols and natural antioxidants [START_REF] Messina | Legumes and soybeans: overview of their nutritional profiles and health effects[END_REF]). However, they also contain anti-nutritional factors such as phytic acid, trypsin inhibitors and phenolic compounds that can lower the protein digestibility and the bioavailability of minerals [START_REF] Kalogeropoulos | Nutritional evaluation and bioactive microconstituents (phytosterols, tocopherols, polyphenols, triterpenic acids) in cooked dry legumes usually consumed in the Mediterranean countries[END_REF]. Legumes represents in 2017, a production above 80 million tons worldwide (http://www.lafranceagricole.fr/actualites/cultures/monde-la-production-delegumineuses-en-hausse-1,2,160468745.html). They are commonly farmed in middle-and lowincome region of the world, for their sustainability and high nutritional profile. The legumes that we will investigate for this review are lupines, peas, chickpeas and soy.

In order to better understand the nutritional values of the ingredients selected, an average composition table will be showed for each. All values come from the CIQUAL tables established by the French national food security agency (ANSES) (« Ciqual Table de composition nutritionnelle des aliments », https://ciqual.anses.fr/). A.

Overview of the main components

Each ingredient selected for this review has either nutritional or rheological assets or both depending on some key components. Previous data have identified some components responsible for those assets at a molecular level and had linked them to one or the other properties. The main ones will be first showed in table 2.

MILK

Casein and casein micelles

Aggregating Gelling

High digestibility (Roesch et al. 2004

A L L

Vitamin A N.A Essential for life (Favier et Dorsainvil 1985) Vitamin B2 N.A Essential for life (Favier et Dorsainvil 1985) Vitamin B12 N.A Essential for life (Favier et Dorsainvil 1985)

Rheological properties

The "functional" properties of an ingredient are defined as properties that affect the behavior of their components during chemical or physical processes (Boye, Zare, et Pletch 2010). Beneath those properties, the rheological ones specifically affect the structure, texture, or the shape of the ingredients under various physicochemical conditions of temperature and pH [START_REF] Ghumman | Functionality and digestibility of albumins and globulins from lentil and horse gram and their effect on starch rheology[END_REF]. In the scope of this review, four functional properties are mainly concerned, given the fact that they have direct application to food industry nowadays: emulsification, foaming, aggregation and gelation. Those functional properties are affected mainly by proteins, because they can interact to form elaborated structures like gels, but also by non-protein molecules such as salt (NaCl) and other minerals, fats, carbohydrates and phenolic compounds. Factors such as the amino-acid composition, size, structure and conformation of the proteins have an influence on the functional properties. Physicochemical conditions like temperature, pH and ionic strength are environmental factors that modify the protein conformation and their stability (Boye, Zare, et Pletch 2010). Taken together, those factors drive the proteins conformation and interactions with other proteins or other molecules.

Emulsification

When two immiscible liquid phases are present, like water and oil, emulsification is a process that will eventually disperse one of the phases into another, forming droplets of one liquid suspended into the other, known as an emulsion. Most often, oil droplets are suspended in water or other aqueous medium [START_REF] Varjani | Critical review on biosurfactant analysis, purification and characterization using rhamnolipid as a model biosurfactant[END_REF]. Components which facilitate that process have the name of emulsifiers. They act by placing themselves at the interface between the two phases, thereby relieving tension forces. Many compounds are tensioactive. Phospholipids for example are present in large amounts in both plant and animal products and are constituent of cells membranes. The polarity of those component makes them very good emulsifiers, because they can protect well the fat droplets, forming a barrier to prevent coalescence. Thanks to that, they're commonly used in the food or pharmaceutical industry [START_REF] Kim | Formation of stable adhesive water-in-oil emulsions using a phospholipid and cosurfactants[END_REF]. Proteins are another main nutrient responsible for the emulsification behavior. Due to their amphiphilic profile, they form a protective layer around the fat droplets and prevent coalescence (Boye, Zare, et Pletch 2010; [START_REF] Karaca | Emulsifying properties of chickpea, faba bean, lentil and pea proteins produced by isoelectric precipitation and salt extraction[END_REF]. The emulsification characteristic of the proteins depends on their structure, size, solubility, conformational flexibility and are directly affected by the hydrophobicity/hydrophilicity ratios of their amino-acid constitution (Boye, Zare, et Pletch 2010; [START_REF] Benjamin | Emulsifying properties of legume proteins compared to β-Lactoglobulin and Tween 20 and the volatile release from oil-in-water emulsions[END_REF]).

Among the ingredients selected in table 2, globulins from legumes and from whey has been described to have high emulsifying activity (Benjamin et In fact, the soluble globular proteins such as legume and whey globulins partly unfold at the interface between droplets and aqueous medium in order to expose their interior hydrophobic amino-acids to the oil phase. Thus, they become amphiphilic and improve their interactions with other nearby proteins at the interface [START_REF] Benjamin | Emulsifying properties of legume proteins compared to β-Lactoglobulin and Tween 20 and the volatile release from oil-in-water emulsions[END_REF]). In general, 7S globulins are better emulsifiers than 11S globulins, because of their smaller size and the presence of glycosylated groups that enhance their flexibility [START_REF] Benjamin | Emulsifying properties of legume proteins compared to β-Lactoglobulin and Tween 20 and the volatile release from oil-in-water emulsions[END_REF]). β-lactoglobulin (β-Lg) and lupine globulins have both an emulsifying power, but a higher concentration of lupine globulin is needed to obtain the same droplets size as with β-Lg [START_REF] Benjamin | Emulsifying properties of legume proteins compared to β-Lactoglobulin and Tween 20 and the volatile release from oil-in-water emulsions[END_REF]). Nevertheless, it shows that legume proteins especially lupine ones (α or β-conglutins) could partially or totally replace animal protein for stabilizing low-fat emulsions [START_REF] Benjamin | Emulsifying properties of legume proteins compared to β-Lactoglobulin and Tween 20 and the volatile release from oil-in-water emulsions[END_REF]; Kohajdová, Karovičová, et Schmidt 2011). Here is an example of the pea (Pisum sativum) protein emulsification process which is representative of the other legume proteins listed above. 4) formation of a viscoelastic film at the interface [START_REF] Burger | Recent progress in the utilization of pea protein as an emulsifier for food applications[END_REF]. In red there are hydrophobic patches on the protein surface that promote the adsorption.

Aggregation

The aggregation phenomenon is commonly obtained by heating globular proteins above their denaturation temperature. Thus, those proteins eventually create variable sized particles. This applies to a variety of globular proteins, either coming from animal or plants sources. Different parameters could modulate the size and the structure of the aggregates, such as protein concentration, heating protocol, pH, nature and concentration of salts (Amagliani et Schmitt 2017). Typically, aggregation is promoted when protein concentration, salt concentration and/or heat are increased. Divalent ions, like calcium, accelerate aggregation more than monovalent sodium. Aggregation is generally faster at the vicinity of the isoelectric pH of proteins. When those soluble proteins are heated, they unfold, expose their hydrophobic regions and irreversibly aggregate by forming hydrophobic interactions, hydrogen bond between acidic and basic polypeptides and thiol/disulfide exchanges [START_REF] Malaki | Effect of soy protein subunit composition and processing conditions on stability and particle size distribution of soymilk[END_REF][START_REF] Benjamin | Emulsifying properties of legume proteins compared to β-Lactoglobulin and Tween 20 and the volatile release from oil-in-water emulsions[END_REF]. Various kinds of structures can be obtained by a heating treatment: spherical particles, flexible strands and semi-flexible fibrils. These constitute the first step to create a gelation process that will be explain later. That is important to say that the formation of aggregates depends on the level of electrostatic repulsions (Amagliani et Schmitt 2017) and on the amino-acid composition of the globular proteins, especially the presence of cysteins with free thiol groups (Hoffmann et al. 1997).

According to literature, this behavior applies to soy globular proteins which represent 90% of the total protein content of soy. Soy globular proteins are constituted of β-conglycinin and glycinin which are 7S and 11S proteins respectively. When these globulins are heated, soluble aggregates begin to form thanks to comparable hydrophobic interactions observed for the whey proteins (Amagliani et Schmitt 2017).

Pea proteins contains 55-65% of globulin consisting of 7S vicilin and convicilin and 11S legumin (Amagliani et Schmitt 2017). As expected, those protein also create aggregates upon heat treatment, by forming hydrophobic interactions and disulfide bonds (Chihi, Sok, et Saurel 2018; Ben-Harb et al. 2018). Interestingly, the presence of sulfhydryl amino acid has an impact on the size of the particles, given that they are crucial to create disulfide interactions. In that way, authors assessed that polypeptides who lacks cysteine residues in their structure couldn't show as good aggregating properties as the others.

Globulins are also present in egg white and have the same behavior as globulins found in other sources. They are known as lysozyme but during the thermal treatment process, not only globulins react to create aggregates. Egg white proteins like ovotransferrin and ovalbumin also react to this treatment by aggregating themselves into β-sheets structures and/or by undergoing thiol/disulfide exchanges. This particular conformation exposes hydrophobic residues that allows stacking and interaction between the β-sheets [START_REF] Mine | Recent advances in the understanding of egg white protein functionality[END_REF].

In milk, caseins that are not globular proteins, are not affected by thermal treatment while the globular whey proteins are (Ben-Harb et al. 2018). Another way to obtain aggregation is to use acidification agents such as the glucono-delta-lactone (GDL) or citric acid, or to use sugar fermentation by lactic acid bacteria to form lactic acid, to reach the isoelectric pH of unfolded acidic proteins, such as the caseins or the denatured globular proteins such as whey proteins. GDL hydrolyses into gluconic acid, releasing protons in the process (Ben-Harb et al. 2018). Several studies have been made with caseins from milk [START_REF] Roesch | Aggregation of soy/milk mixes during acidification[END_REF]) and demonstrated that casein aggregates begin to form at pH 5.3. Using rennet is another way to form aggregates commonly used in the cheese industry. This protease hydrolyses the Phe105-Met106 bond of the -casein, one of the four caseins that is mainly present at the surface of the casein micelles, cleaving off a casein fragment responsible for electrostatic repulsion and creating an hydrophobic zone that allows aggregation (Ben-Harb et al. 2018; Grygorczyk et Corredig 2013).

Although most of the aggregation studies have been made on heat-denatured whey proteins for their high solubility and aggregating power, fewer literature exists on the acidinduced aggregation of denatured legume proteins. However, it has been shown that during acidification, the concentration of protons increases, and near pH 5.8 [START_REF] Malaki | Effect of soy protein subunit composition and processing conditions on stability and particle size distribution of soymilk[END_REF]), gradually neutralize surface charges of the soy glycinin and β-conglycinin. Then, the basic sub-unit of glycinin folds into a particle, while the acidic sub-unit and the α and α' subunits of βconglycinin comes over it (Grygorczyk et Corredig 2013) To sum up, the globulins which eventually destabilize, and begin to form hydrophobic interactions (Malaki Nik et al. 2009) by unfolding themselves and finally aggregate into particles (Grygorczyk et Corredig 2013).

Gelation

Gelation is an important reaction widely used in food industry and could be defined by a reaction leading to an infinite aggregation stabilized by several kind of interactions including electrostatic and hydrophobic interactions, hydrogen and/or disulfide bonds [START_REF] Ma | Thermal processing effects on the functional properties and microstructure of lentil, chickpea, and pea flours[END_REF]). An indicator known as the least gelling concentration (LGC) is commonly used to define the lowest concentration of gelling agent required to form a stable gel (Boye, Zare, et Pletch 2010). The gelation point is also known to be related with two indicators: the storage modulus that represents the capability of a matter to be more solid-like and noted G', and the shear storage that represents its capability to be more liquid-like, noted G''. Usually the gelation point is defined as the moment when G''>G' [START_REF] Malaki | Effect of soy protein subunit composition and processing conditions on stability and particle size distribution of soymilk[END_REF]). The water holding capacity (WHC) represents the capability of a food to trap water and is often used as an indicator of gel quality. Protein gels work the same way and consist in a formation of a three dimensional network that traps large amount of water with a small amount of proteins [START_REF] Mine | Recent advances in the understanding of egg white protein functionality[END_REF]. Gelation is affected by the same factors as aggregation: pH, temperature, and ionic strength (Zhang, Jiang, et Wang 2007; Grygorczyk et Corredig 2013) and also depend on the protein concentration, type of proteins but also the presence of non-protein components like carbohydrates or lipids ( The structure of the final gel depends on the structure and size of the aggregates that built it, which themselves depend on physicochemical conditions like pH and salt concentration. At least , three types of aggregates are formed by heat-induced aggregation : spherical particles, flexible strands and semi-flexible fibrils (Amagliani et Schmitt 2017), leading to different gelation behaviors and different gel structures. In fact, a second aggregation could occur between those three types of aggregates. Spherical particles and flexible strands associates to create larger aggregates and eventually form a turbid or a translucent gel, respectively (Amagliani et Schmitt 2017; de la Fuente et al 2002; Foegeding et al 1998; Renkema et al 2000). A microgel is a particle, composed of a stable network consisting in cross-linked molecules maintained by covalent bond(s) and intermolecular interactions (Amagliani et Schmitt 2017). In soy "milk", heat-induced aggregation may lead to this particular structure as reported by Chen et al (2014). Its structure is composed by a hydrophobic core containing β subunits and some 11S basic polypeptides enveloped/surrounded by α and α' subunits of 7S and acid polypeptides of 11S. The core is stabilized by strong disulfide bonds and hydrophobic interactions.

Using GDL with addition of calcium sulfate is a common way to make soy gels resulting in tofu [START_REF] Malaki | Effect of soy protein subunit composition and processing conditions on stability and particle size distribution of soymilk[END_REF]. By using GDL to acidify the media, a gel may result as an aggregation of the previously heat-denatured soymilk proteins. But contrary to the heat-induced method, gels made by acidification are more stabilized by non-covalent interactions like saltbonding, hydrogen bonding and Van der Walls forces, rather than by thiol/disulfide bonds (Grygorczyk et Corredig 2013). Environmental pH plays a major role into gel formation and allow setting the proteins at their neutral charges. Once the pH of the media approaches the isoelectric point of the proteins, β subunits of β-conglycinin are the first to destabilize followed by α and α' subunits of β-conglycinin who participate to form a stable gel network. Neutralizing the repulsive charges allows the proteins to come in close contact. The formation of hydrogen bonds at this moment will determine the gel stiffness [START_REF] Malaki | Effect of soy protein subunit composition and processing conditions on stability and particle size distribution of soymilk[END_REF]). [START_REF] Malaki | Effect of soy protein subunit composition and processing conditions on stability and particle size distribution of soymilk[END_REF] reported that modifying the GDL concentration does not affect the gelation point; however, it does greatly impact G' by affecting the time needed to the proteins to arrange together to form a gel. Finally, higher ratios of globular protein compositions between glycinin (11S)/βconglycinin (7S) may increase the storage modulus G' of the gels formed, where G' represent the stiffness of the gel [START_REF] Yagasaki | Potential improvement of soymilk gelation properties by using soybeans with modified protein subunit compositions[END_REF]. In fact, gels formed around pH 5,6-5,8 with higher proportion of glycinin were firmer than gels made of pure β-conglycinin, because glycinin formed larger aggregates [START_REF] Malaki | Effect of soy protein subunit composition and processing conditions on stability and particle size distribution of soymilk[END_REF]). However, the isoelectric point of β-conglycinin (4.5-5.0) is lower than that of glycinin (6.3-7.0), due to more negatively charged subunits. Therefore, the media need more H + protons to aggregate β-conglycinin and the gelation point at acidic pH depends mainly on the proportion of that protein. -Conglycinin and glycinin are the main globular proteins implicated in the formation of soy gels, but it is actually glycinin that affects the firmness of the gels. Under these conditions, it shows that soy cultivars with little β-conglycinin amount both improve the firmness of gels and require less acidifier [START_REF] Kohyama | Rheological studies on the gelation process of soybean 7 s and 11 s proteins in the presence of glucono-.delta.-lactone[END_REF].

It is also possible to acidify soy "milk" with lactic acid bacteria. Proceeding this way, it has been shown that the pH measured at the gelation point is higher than that using the GDL way (Grygorczyk et Corredig 2013). This could be explained by the slower fermentation time of soy "milk" by bacteria that allows more protein rearrangement during acidification. However, it does not affect the final gel structure.

During acidification of milk proteins, neutralization of the casein micelles (pHi = 4.6) leads to the formation of a gel network. When unheated milk is used, gelation occurs at pH 5. That is important to note that undenatured whey proteins, mainly constituted of β-lactoglobulin do not impact the gelation process [START_REF] Roesch | Aggregation of soy/milk mixes during acidification[END_REF]). In contrast, in heated milk, the whey proteins are denatured and form aggregates that increase the gelation point to a higher pH. Thus, it has been shown that whey proteins play an important role in gelation mechanisms of heated milk by reinforcing the gel network [START_REF] Roesch | Aggregation of soy/milk mixes during acidification[END_REF]).

In egg white, gelation properties are also due to globular proteins and obey the same rules as previously described for the other globular proteins [START_REF] Mine | Recent advances in the understanding of egg white protein functionality[END_REF] with respect to pH, ionic strength, protein concentration and/or heating method. The aggregation process can produce the same types of aggregates than those reported by Amagliani and Schmitt (2017) : spherical particles, flexible strands and semi-flexible fibrils. Several methods have been reported to be effective for aggregation and gelation. Heat treatment leads to the denaturation and aggregation of ovotransferrin, lysozyme and ovalbumin [START_REF] Mine | Recent advances in the understanding of egg white protein functionality[END_REF]. The addition of salts like iron or aluminum increases the denaturation temperature of the egg white, maybe due to the ovotransferrin capabilities to increase its stability by binding metallic ions [START_REF] Mine | Recent advances in the understanding of egg white protein functionality[END_REF]. The gelation process for egg white is defined by the three steps described below. First, the heat treatment induces the partial unfolding of egg white proteins and thus, the formation of spherical aggregates via hydrophobic interactions. Second, the already formed aggregates reinforced themselves through disulfide bonds that even though not necessary for gelation can increase the stability of the structure. Finally, upon cooling, a large formation of hydrogen bonds leads to an increase of the structure elasticity. It has been also reported that ovalbumin gels, formed by a thermal treatment are the result of cross-linked β-sheet structures, stabilized by hydrophobic interactions [START_REF] Mine | Recent advances in the understanding of egg white protein functionality[END_REF].

Since alkali treatment is a relatively old conservation technique for eggs, it is also useful to study aggregation and gelation behavior of egg white at high pH values. As observed at other pH values, heat causes a denaturation of the egg white proteins followed by an unfolding and an exposition of their hydrophobic structure. Thus, inter-proteins interactions could be made as well as disulfide bonds and eventually lead to gel formation. Under these conditions, no hydrogen bonds can however be created [START_REF] Gharbi | Effect of processing on aggregation mechanism of egg white proteins[END_REF].

The yolk is constituted by non-soluble protein aggregates known as granules, hosted in the plasma which is the yellow fluid. Thus, granules could easily be separated from plasma by centrifugation. Those granules count for approximatively 50% of yolk proteins, the other 50% being contained in the plasma [START_REF] Valverde | Egg yolk and egg yolk fractions as key ingredient for the development of a new type of gels[END_REF]. Plasma is rich in low density lipo-proteins (LDLs) and livetins, while granules are rich in high density lipoproteins (HDLs) and phosvitin. Upon heating, egg yolk proteins denature the same way as the egg white proteins, but form a much harder and dense gel, due to its higher solid content. Thus, the egg yolk protein gels are commonly accepted to be among the hardest ones (Zhang, Jiang, et Wang 2007).

Foaming

Foams are defined by air bubbles suspended in a continuous phase that is usually an aqueous medium (Amagliani et Schmitt 2017; X. [START_REF] Li | Foaming characterization of fresh egg white proteins as a function of different proportions of egg yolk fractions[END_REF]). Making foams is usually achieved by mechanical whipping at high speed (Amagliani et Schmitt 2017). Quality of foams can be characterized by three indicators, the foam stability (FS), the foam expansion (FE) and the foam capacity (FC). FC and FE are expressed as the volume (%) of foam produced with a volume of initial liquid (FC) and the volume increase depending on the foaming protocol (FE). Meanwhile, FS is measured as the increase of the liquid phase in time units due to drainage, and is an indicator of the ability of the foaming agent to form a protective layer to retain water and prevent foam coalescence (Boye, Zare, et Pletch 2010; [START_REF] Ma | Thermal processing effects on the functional properties and microstructure of lentil, chickpea, and pea flours[END_REF]. Foaming properties of a mixture are affected by aeration conditions, temperature, pH and ionic strength and are also dependent on the protein content as well as other components like carbohydrates that may modify the viscosity of the aqueous phase. As emulsions, foams are thermodynamically unstable systems that could be stabilized by the amphiphilic properties of the proteins. By unfolding themselves, they rapidly adsorb at the air-water interface and rearrange it in order to create a protective film that relieves interfacial tension (Boye, Zare, et Pletch 2010; Mine 1995). Likely, they act as a protective layer around the air bubbles forming a widely range of interactions such as hydrogen bonds, electrostatic and hydrophobic interactions [START_REF] Ma | Thermal processing effects on the functional properties and microstructure of lentil, chickpea, and pea flours[END_REF]). Size, solubility, and ratios of protein isolates affect the foaming properties of a mixture as well. Several studies report the foaming abilities of unfolded whey protein aggregates. In fact, heat induced (85°C-15min) whey proteins aggregates at a pH of 5.9 could act as foams stabilizers by a similar mechanism than emulsions (Amagliani et Schmitt 2017). β-Lactoglobulin (β-lg) is by far the globular protein from whey the most capable to make foams. Thermal aggregates of β-lg were found to be effective to create foams, as they provide a cohesive interfacial film between air and the aqueous medium. It has also been reported that FS is function of the aggregate size.

Egg white contains proteins that show high foaming abilities. This ingredient is widely used for a long time in cooking or in the food industry to make cakes, cookies, mousses and other air suspensions [START_REF] Li | Foaming characterization of fresh egg white proteins as a function of different proportions of egg yolk fractions[END_REF]). Foaming properties of egg white have been shown to be correlated to globulins as well as ovalbumin [START_REF] Mine | Recent advances in the understanding of egg white protein functionality[END_REF]. Like other protein sources, electrostatic and hydrophobic interactions are essential for FC of egg white proteins. In addition, the ability of the egg white proteins to create disulfide bonds can impact the foaming properties since those bonds makes a less flexible structure [START_REF] Mine | Recent advances in the understanding of egg white protein functionality[END_REF]. That is important to note that only the egg white contains foaming agents. Even in small amount, egg yolk contamination can dramatically reduce the foaming properties of egg white. This could partially be explained by the high amount of fat in egg yolk, who act as a defoaming agent and greatly impact FC and FE.

Lupine protein possesses foaming capabilities as reviewed by Kohajdová, Karovičová, and Schmidt (2011). In this paper, authors assessed that lupine flour has comparable foaming capabilities to the egg albumin located in egg white. Prior to heat-treatment by boiling, these flours form a consistent foam which is like uncooked egg white, in terms of texture and microstructure. Nevertheless, fats in lupine could be a problem for FC and FE. In fact, polar lipid such as glycolipid and phospholipids absorb at the air-liquid interface and consequently are foam stabilizers. But non-polar lipids like triglycerides often create weaker layers at the interface and can be desorbed more easily [START_REF] Kohajdová | Lupin composition and possible use in bakery: a review[END_REF]. Other studies have reported that fats in general are considered as a defoaming agent [START_REF] Li | Foaming characterization of fresh egg white proteins as a function of different proportions of egg yolk fractions[END_REF]). Fortunately, the defatting processes does not affect the lupine protein and consequently increases the FC.

C. Nutritional properties implicated and health attributes

The selected ingredients have specific nutritional properties, depending on their animal vs vegetal origin.

Human organism needs essential amino-acids for a good functioning. According to the OMS, these needs are shown in table 3 and are compared with the contribution of the different ingredients selected for this review. Thus, it will serve as a reference to evaluate the nutritional quality of protein profiles of these ingredients. Milk is known to be a source of balanced amino acids essential to newborns, but actually poorer than other animal products like egg white and yolk that is usually taken as a reference. Milk also contains ~4% fats where saturated fatty acids are much more important than unsaturated ones. Thanks to food engineering, it is possible to modulate fat content by creaming processes. Milk fat is also a good source of cholesterol as well as vitamins. Lactose is subject to discussions, since it is the major carbohydrate present in milk and has been recognized to be less digestible by the human adult organism. This intolerance to lactose can be reduced and even removed by consuming yogurt, in which the bacterial -galactosidase is able to replace the human deficient enzyme during digestion. Nevertheless, the galactose released during the lactose hydrolysis has health benefits, since it is involved in the synthesis of cerebrosides, an important lipid for the nerve tissue constitution. Although milk is a poor source of oligoelements, the calcium and phosphorus are important source to the bone growth and development. Caseins from milk have been shown to be highly digestible (98.3% w/w), and often serve as a reference to measure this parameter in other food systems. Protein digestibility of legumes selected are the follow : Soy bean : 71.8% ; Pea ; 60.4-66.5% ; Chickpea : 89% (Boye, Zare, et Pletch 2010) ; Lupine : 90.8% (Regina Pereira [START_REF] Monteiro | Evaluation of the chemical composition, protein quality and digestibility of lupin (Lupinus albus and Lupinus angustifolius)[END_REF]. Besides those nutritional properties, milk proteins, and especially whey proteins contain biologically encrypted sequence of bioactive peptides that are released during food processing by endogenous milk enzymes or bacterial proteolytic enzymes, and/or during digestion. The αlactalbumin is a rich source of tryptophan that is the precursor of the serotonin in brain content [START_REF] Sharma | Chapter 17 -Whey Proteins in Functional Foods[END_REF]. Whey proteins also have the ability to regulate the food intake, by regulating the satiety signal (Sharma 2019). [START_REF] Mohanty | Milk derived bioactive peptides and their impact on human healtha review[END_REF] reported that casein and β-lg proteins also contain bioactive peptides that have health benefits such as radical scavenging activity and inhibition of lipid peroxidation.

In general legume proteins show an interesting nutritional profile with high amount of essential amino acids such as lysine, leucine as well as aspartic acid glutamic acid and arginine. However, low amounts of methionine, cysteine and tryptophan have been detected, since these are contained in the albumin fraction which is minor regarding to the overall globulin content (Boye, Zare, et Pletch 2010). In particular, soy proteins have been shown to have high digestibility (71,8%) and a well-balanced amino acid profile (Boye, Zare, et Pletch 2010; Amagliani et Schmitt 2017). Pea proteins contains more essential amino than animal products except for methionine and tryptophan, which are much more present in eggs (see table 3). In addition, some soy and lupine proteins have been reported to be potential allergens. Studies have reported that children who are subject to peanut allergy are also allergic to lupine and soy, since the three are belonging to the legume family. However, other legumes like pea and chickpea could represent an alternative for those allergic people up to now (Boye, Zare, et Pletch 2010), since the protein they contain (Legumin and Vicilin) are hypoallergenic and have a high nutritional value (Amagliani et Schmitt 2017). Nevertheless, no one can exclude that a higher contact of such legume proteins to a larger number of people will also provoke allergy in the future. It is also important to note that legumes are non-gluten plants which constitute a good consumption alternative to cereals products, in addition of their other nutritional properties [START_REF] Kohajdová | Lupin composition and possible use in bakery: a review[END_REF]. Legumes and cereals can be used in combination to fulfil a complete essential amino-acid profile.

Legumes often contains good amounts of antioxidant molecules such as tocopherols which prevent lipid peroxidation. In that way, tocopherols are particularly high in chickpeas [START_REF] Kalogeropoulos | Nutritional evaluation and bioactive microconstituents (phytosterols, tocopherols, polyphenols, triterpenic acids) in cooked dry legumes usually consumed in the Mediterranean countries[END_REF]. Soy is also a good source of phenolic compounds which possesses strong antioxidant properties [START_REF] Ismail | Effect of mixing soy milk with buffalo or cow milk on the chemical composition, microbial properties and sensory evaluation of yoghurt[END_REF]). In addition, soybean also contains large amount of isoflavones, a molecule from the phytoestrogen family, that has been shown to reduce the risk of hormonal and age related diseases [START_REF] Jiang | Food quality improvement of soy milk made from short-time germinated soybeans[END_REF][START_REF] Ismail | Effect of mixing soy milk with buffalo or cow milk on the chemical composition, microbial properties and sensory evaluation of yoghurt[END_REF]). Lupine has quite an interesting antioxidant activity, because of the presence of phenolic compounds which are mainly tannins and flavonoids. As reported by [START_REF] Kohajdová | Lupin composition and possible use in bakery: a review[END_REF] lupine has slighter less anti-nutritional compounds like trypsin inhibitors, phytic acid and complex carbohydrates, lectins and saponins than other legumes. Also, phytosterol content of the legumes is quite interesting since they are present in relatively large amount in those plants, especially in chickpeas and lupines. They are known to compete with the dietary cholesterol thus limiting absorption by the intestine. Thus, they could offer a protective effect against LDL oxidation and preventing cardiac diseases. They also possesses anticancer, anti-inflammatory and antioxidant activities [START_REF] Kalogeropoulos | Nutritional evaluation and bioactive microconstituents (phytosterols, tocopherols, polyphenols, triterpenic acids) in cooked dry legumes usually consumed in the Mediterranean countries[END_REF]. Squalene is an intermediate in the biosynthesis of sterols. It has been reported that this component contributes to the inhibition of several forms of cancers such as lung, colon and skin cancer. Although squalene exists in very low amount in legumes, lupine is a relatively good source of it [START_REF] Kalogeropoulos | Nutritional evaluation and bioactive microconstituents (phytosterols, tocopherols, polyphenols, triterpenic acids) in cooked dry legumes usually consumed in the Mediterranean countries[END_REF]).

However, legume seeds may contain some anti-nutritional factors such as enzyme inhibitors like trypsin, chymotrypsin inhibitors, phytic and oxalic acid, complex carbohydrates and phenolic compounds. In fact, these components may cause a diminution of protein digestibility and mineral bioavailability. Complex carbohydrates contained in legumes, such as stachyose and raffinose, have a particularly low digestibility and are often the cause of intestinal uncomfort, while they are also bifidogenic factor implied in the microbiote homeostasis. If not previously treated by heating, dehulling or soaking, such anti-nutritional compounds can have an impact on the overall digestibility of legumes proteins and their mineral bioavailability (Boye, Zare, et Pletch 2010; [START_REF] Kalogeropoulos | Nutritional evaluation and bioactive microconstituents (phytosterols, tocopherols, polyphenols, triterpenic acids) in cooked dry legumes usually consumed in the Mediterranean countries[END_REF][START_REF] Messina | Legumes and soybeans: overview of their nutritional profiles and health effects[END_REF][START_REF] Weaver | Dietary calcium: adequacy of a vegetarian diet[END_REF]. Furthermore, phytic acid is known to lower the calcium bioavailability. On the other hand, heating dramatically reduces the rates of trypsin inhibitors, lectins, and undigestible oligosaccharides, and improves the overall legume proteins digestibility except for phytic acid, which is not particularly affected by this treatment [START_REF] Jiang | Food quality improvement of soy milk made from short-time germinated soybeans[END_REF]. It has also been reported that phytic acid contributes to reducing the cancer risk, thanks to its antioxidant properties [START_REF] Messina | Legumes and soybeans: overview of their nutritional profiles and health effects[END_REF]. In lupine, the major anti-nutritional components are alkaloids from the quinolizidine group such as lupinine, lupanine, sparteine and others (Kohajdová, Karovičová, et Schmidt 2011) that are partially or even completely removed through selection of "sweet" lupin varieties (Lupinus albus and Lupinus angustofolius).

III. Properties of mixes between animal and vegetal products

In the context of a need for a more balanced animal to vegetal protein ratio in human diet, mixes between milk or egg products with legumes are an emerging field of research in food industry and food design. Most of the articles are actually very recently published in this area. The main interest is relied on technological properties of proteins and namely of legume proteins. Actually, rheological properties of certain legumes look like those commonly exploited in dairy products. In addition, the nutritional properties of legumes could provide some added values to the products made this way, with respect to their also known antinutritional properties. Several data have shown that is it possible to combine those products to make a stable mixture and exploit their rheological assets to create a wide range of applications. In the part of this review, we expose some mixes that have already been proposed, their benefits and limits regarding to the method employed and their potential application for food industry.

Ismail et al (2017) have attempted to produce mixes between 25% soy "milk" with 75% buffalo or cow milk in order to create a yoghurt-like product. Then, the mix was inoculated with a commonly-used yoghurt starter containing both Streptococcus thermophilus and Lactobacillus bulgaricus. Several parameters were measured such as the chemical composition (Total solids, fats, total nitrogen and ash content), the free fatty acid content (FFA), the saturated (SFA) and unsaturated (USFA) fatty acids, the monounsaturated (MUSFA) and polyunsaturated fatty acids (PUSFA) content, the short chain fatty acids (C8-C12), the medium chain fatty acids (C14-C16), the long chain fatty acid (<C16), and the free amino acids content (FAA). A microbial analysis and a sensory evaluation of yoghurt were also performed. Results showed that the incorporation of soy "milk" can produce a highly nutritional yoghurt, with high amount of USFA and essential amino acids, without reaching the contents of pure milk samples yet. In yoghurt-like product containing 0.5, 10 or 15% of soy "milk", [START_REF] Altahir | Effect of partial substitution of soy milk on the chemical composition and organoleptic attributes of yoghurt[END_REF] showed that the proteins and fat content were significantly lower in the 15% soy/milk yoghurt, probably because of the lower protein and fat content contained in soy, and legumes in general. They also showed that depending on the bacteria strain used for fermentation, different acidification rates can be obtained. Thus L. bulgaricus that was used in this study has a low ability to ferment the complex soy carbohydrates commonly founded in legumes. However, the sensory evaluation showed that the fermentation contributed to eliminate the "beany" flavor of soy and thus, the organoleptic properties of the final product were quite acceptable.

Lin, Hill, and Corredig (2012) investigated the formation of a mixed gel containing soy "milk" and reconstituted bovine skim milk with a final protein concentration of 3,4% and a ratio of 60:40 soymilk proteins to milk proteins. All gelation processes were conducted at 30°C, without previous thermal treatment. The gelation method was induced by GDL acidification and/or rennet addition. Results showed that it was possible to create gels with this kind of mixture. Particle size distribution of the mixtures was comparable to those with soy "milk" alone. Gels formed with GDL alone or in combination with rennet were comparable in terms of structure with those formed by soy "milk" alone. However, no gelation process was observed when only rennet was used. This highlights the importance of the acidification process and confirms that rennet, that reacts on very specific amino acid sites and is known to destabilize casein micelles, has no effect on soy proteins, regarding gelation. However, rennet was able to react on caseins in soy-casein mixes and aggregates were formed trapping soy and milk proteins together, forming unique microstructures. The gelation point for the mix occurred at pH 6.1, instead of 5.0 for milk. It was concluded that the gelation process was driven by the soy proteins, because the gelation occurs although the pH was insufficiently low to cause aggregation of milk proteins. More specifically, the behavior of pre-heated (90°C) soy "milk"-whey protein isolates (WPI) aggregates has been investigated during acidification by GDL [START_REF] Roesch | Aggregation of soy/milk mixes during acidification[END_REF]). Different ratios were tested from 100:0 (w/w) WPI/soy proteins to 0:100 (w/w) with 70/30, 50/50, 10/90 and 30/70 intermediates, all with a 6% final protein content, in presence of 0,1M of NaCl. The gels formed were analyzed both by dynamic oscillatory measurement and confocal microscopy. Results showed that all mixes formed gels upon heating. Moreover, WPI seems to play a major role in the network formation. No gelation was observed with pure soy proteins or at high soy protein content (90/10). The confocal microscopy also showed that heat treatment (90°C) increases the size of aggregates particles and proteins clusters before acidification. G' was the highest for gel formation with a milk/soy protein ratio 70/30 and does not increase with further addition of soy proteins anymore.

Ben-Harb et al (2018) compared the gelation process suspension of pea proteins, milk proteins or a ratio of 1:1 pea/milk proteins, with a constant protein concentration of 14.8%. More precisely, three gelation techniques were used for gelation: a GDL treatment without heating, an enzymatic treatment with chymosin or transglutaminase (TGase) without heating and a thermal gelation (80°C -1h and cooling to 20°C). The rheological properties were followed by a rheometer and the microstructure by confocal laser microscopy in order to analyze the gelation process and the gel's microstructure. Results showed that thermally induced pure pea gels and mixed gels had comparable rheological and microstructural properties. It has also been shown that addition of fats reinforces the mechanical properties of the pea/milk gels. In the thermally induced gelation, the presence of pea protein led to much more stiffer gels, perhaps because of increased protein crosslinking with covalent bonds. Like soy, pea proteins drove the gelation process, creating bonds with milk proteins to form a threedimensional network. In contrary to milk/soy gel, the pea/milk gel have a much greater elasticity as well as the pure pea and milk gels alone. Also, the study reported that higher concentration of pea proteins yielded to a much stiffer gel after the thermal treatment. In pea/milk gels, those findings mean that the stiffness depends on the whey protein concentration. Nevertheless, mixed gels were firmer than the pure milk gels and equal to pure pea gels. In the enzymatically-induced gelation, the G' of the mixed gels was lower than the pure milk or pea gels, probably because the TGase is more susceptible to form bonds between similar proteins than different proteins. In the acid-induced gelation, the pure pea and mixed suspensions gelled quicker than the pure milk suspension, due to a higher gelation point of the pea proteins. All these findings show that the heat-induced gelation works well for mixed suspensions, as G' was the greatest among all gels. That could be explained by a co-gelation phenomenon between pea and milk proteins, creating covalent bonds in the process. However, the nature of those bonds has not been explained. Also, the enzymatic treatment produces more elastic and strain resistant gels than the other gelation techniques. The addition of fat into the suspensions has also been studied, as it conducts to an increase of G' for all gels, probably because the droplets act as fillers in the network.

Another study investigated more specifically the acid gelation of mixed thermal aggregates of pea globulins and β-Lg [START_REF] Chihi | Acid gelation of mixed thermal aggregates of pea globulins and β-lactoglobulin[END_REF]. The acid gelation was conducted by GDL and the authors measured the rheological properties, the microstructure and the WHC of the formed gels. Results showed that the gels formed by thermally-induced aggregates of pea globulins and β-Lg have better elasticity properties and WHC than these containing pure non-thermal induced aggregates of pea globulin and β-Lg. More fibrillate structures were found in those gels, conducting to a much more porous and irregular structure with reduced elasticity and WHC. Those finding show that is better to heat both types of proteins prior to an acid induced gelation process. In addition, it has been reported that an increase in β-Lg amount leads to enhanced gelling properties. [START_REF] Zhao | Formation and Properties of Recombined Soymilk and Cow's Milk Gels: Effect of Glucono-δ-Lactone[END_REF], investigate the properties of recombined soymilk and bovine milk gels by acidification of the media with different levels of GDL (0,1% ; 0,15% ;0,20%, 0,25% ; 0,30% ; 0,30%). Gels contained 20% bovine milk and 80% soymilk and were heated to 100°C for 10 min before addition of GDL. The gel formation was conducted at 75°C. Measurements were made on protein composition, WHC, textural properties, SEM (scanning electron microscope) analysis, particle size test, sensory evaluation and attributes analysis. Results showed that hydrophobic interactions and disulfide bonds were the main driving forces to the gelation process in mixtures with bovine milk and soymilk. After 2h of cooling, textural analysis was made. Texture properties were driven by GDL, creating protons H + that cause a pH decrease in the media. Results suggested that addition of GDL greatly affects the structure of the gels made. Springiness, which is the ease of the gel to be broken into smaller pieces was at maximum for a value of 0.25% GDL. Hardness was a dependent of the concentration of GDL, with much harder gel as the concentration of GDL increases. WHC does not shown significant differences regarding the GDL concentration. However, it is to note that the formation of a network improves the WHC of the gels. Regarding the microstructure, the minimum concentration of GDL to efficiently form a gel with protein aggregation was 0.15%. Adding more GDL did not result in a more uniform and homogenous structures, as well as the particle size distribution, where the aggregates ranged from 10.3 to 14.3 µm. The sensory evaluation of gels formed depends significantly of the amount of GDL added. Gels with 0.25% GDL tends to have the highest scores at color and flavor. Finally, the attributes analysis revealed that mixed gels showed a protein value (3.7%) between pure bovine milk gel (3%) and pure soy gel (3,. %), as well as a crude fat content (1.8%), located between pure bovine milk gel (3.3%) and pure soy gel (1.6%).

Silva et al (2018), studied the gelation behavior of aqueous micellar casein (MC), supplemented with some soy (SP) and pea (PP) globular protein (GP), in comparison with a standard : addition of whey protein (WP). Gels contained 6% w/w of MC supplemented with the different globular protein content ranged between 0-6% w/w. pH of the suspension was 5.6-6. Heat induced gelation ramped with 5°C/min from 20°C to 90°C and was held at 90°C for 1h and then cooled as the same rate. Different parameters were measured: protein composition by SDS-PAGE, and rheological properties such as stiffness. Results suggested that the different suspension gelation point temperature was dependent on the quantity of GP added but also vary between GP sources. The gelation critical temperature was higher in the order of SP>PP>WP. This could be explained by the fact that GP have properties to bind the calcium present, reducing by the way the availability of it for the casein to make bridges. The stiffness of the gels were significantly stronger at 90°C for MC-WP gels only. With supplementation with SP, the gel stiffness increased not significantly at pH 5.6 and 5.8 and decreased at pH6. Li and Damodaran (2017) investigated the in vitro digestibility and IgE reactivity of enzymatically cross-linked heterologous protein polymers. The suspensions tested were as follows: WPI, soy protein isolate (SPI) and casein (CN). Each suspension was a 2% of SPI, WPI or CN. For the mixes: WPI-SPI, WPI-CN and SPI-CN, 2% of each protein sources were mixed together at 1:1 (w/w) ratio to give a solution with 1% of each. Gelation process used TGase without pre-heating treatment. In vitro digestion, protein composition, and immunoassay analysis were conducted. Results explained that the TGase catalyzes the formation of isopeptide bonds between primary amines groups and carboxamide group of glutamine residues, resulting in a formation of a crosslinked network. The network is composed by branched-brain strains that were unique depending the different sources of protein used. The gelation process partially covers IgE binding sites which lower the potential allergenicity of the proteins. Since the network formation mainly depends on the glutamine to lysine ratio and the distribution of these residues in the protein's structure, some proteins like β-Lg who has been reported to have a low ratio Glu-Lys could presents large gaps in the resulting network formation, allowing IgE to bind. Thus, authors noted a decrease in IgE reactivity in SPI-WPI and SPI-CN gels to 10% of their original reactivity. This was not the case in WPI-CN gels. This ability must relate to the high glutamine content of SPI which leads in an effective high polymerization with high branched chains who can disrupt epitopes of WPI and CN. The in vitro digestion shows that peptides released form SPI and CN in all polymer products did not affect the IgE reactivity, which dropped to 0 after the gastric phase digestion. Counter to that, peptides released from WPI (single or mixed) showed a residual 5-20% IgE reactivity during the entire digestion. Taken together, those results suggest that GDL gelation led to a better disruption of IgE epitopes in gels with CN, SPI, and SPI-CN than in WPI systems. [START_REF] Silva | Heatinduced gelation of mixtures of micellar caseins and plant proteins in aqueous solution[END_REF] investigate the heat-induced gelation of mixtures of micellar caseins and plant proteins in an aqueous solution. Gelation process were made using different mixtures with MC and plant protein (SP, PP) ranged from 100/0 to 0/100 MC/SP, PP for a total protein content of 4%, 6% and 8% at pH 5,8 and 6. The gelation was made by heating treatment starting at 20°C with a 5°C/min rate to 90°C. Then the mixtures were held at 90°C for 1h and then cooled from 90°C to 20°C at a rate of 5°C/min. Rheological properties of mixes and structural analysis by confocal microscopy were made to qualify the resulting gels. The solubility each kind of proteins was also calculated in aqueous solution with 2% protein content. Results shown that in water, plant proteins have a lower solubility than MC and as a function of the pH. In fact, solubility of SP and PP decreased below pH 6 and 6.5 because it approaches the isotonic point of protein which are 4.4 and 4.5 for soy protein isolate (SPI) and pea protein isolate (PPI) respectively. At pH> 6.5 SPI showed a better solubility than PPI. Authors explain that these results limit the use of plant proteins in food systems but only when the proteins were not thermally treated. Regarding the rheological properties in MC suspensions, G' increased quickly around 50-60°C for a concentration of 4% (w/w). Then, the critical gelation temperature decreased when the MC concentration increased (up to 40°C at 8% w/w) and at lower pH values. When MC was replaced by SP and PP the critical temperature of gelation increased at the same pH values independently of the final protein content. This effect could be explained by the fact that plant proteins better chelate calcium than MC, bridging peptides more effectively. The effect was stronger for SP compared to PP. Confocal microscopy revealed that MC and plant protein do not aggregates one another/each other, forming independent networks. Thus, stiffness of the mixed gels at a given total protein content was lower when MC or plant proteins were replaced by their respective counterparts (MC, PP or SP). Gel stiffness was minimal when mixture contained 40% SP or 70% PP of the total protein at pH 5.8. However the formation of interpenetrated networks from MC and plant proteins should increase the WHC (not measured in this study), as the authors report an inhibition of the syneresis in the mixed gels, which not the case with the individual protein gels.

IV. Conclusion and perspectives

Preparing mixtures with both animal and legumes component is achievable and could have a great impact on the development of food industry and a great interest in a near future. Legumes are sustainable and affordable resources, their proteins are also valuable and show an interesting nutritional profile. Rheological properties of legumes and milk are compatible and make interesting synergies, mainly in terms of aggregation and gelation protocols.

Pea/milk mixes and soy/milk mixes are currently the most represented mixes in this literature review, and no data was found about designing mixes with egg as the animal product. Making gels which involve soy and milk proteins is a good start and could be achieved by several techniques, including those already used in the dairy industry. In those mixtures the gelation process is mainly driven by soy proteins. Acid-induced gels show the best results in terms of stability and firmness and the gels made this way often have a strong storage modulus, near the pure milk gels which makes it more solid-like. According to the literature varying the concentration of both soy and milk proteins may also lead to the creation of a wide range of gels and unique microstructural profiles.

Making gels with pea proteins and milk proteins (caseins and whey proteins) are also possible, even if it does not lead to the creation of a product on the market now. It could however conduct to several food application in terms of texturation. For now, it is possible to assess that mixed pea/milk gels have comparable rheological and microstructural properties. Fat can play a role on the gelation process as they increase the stiffness of the products. Like the soy proteins, pea protein leads to the gelation process of mixes. Pea proteins also show a greater elasticity which could conduct to food applications different than that showed with the soy/milk mixes.

Although legumes show good rheological properties, they are also known for their nutritional properties and health benefits and it is important to remember it when designing new food applications. Because of their relatively good amount of antioxidant molecules and phytosterol they could contribute to reduce the risk of developing several diseases. However, legumes also contain some anti-nutritional factors that can lower the digestibility and are often cause of intestinal discomfort. Fortunately, the heating processes and fermentation often achieved to reduce the amount of the anti-nutritional components in the final product. Apart from sensory evaluation and crude composition analysis, studies reviewed on mixes do not report health benefits for now, as they are mainly focused on more technological aspects.

Despite of the rheological properties, fermentation by lactic bacteria leads on more concrete products. Soy/milk mixes yoghurt-like product has already been made under laboratory conditions, using common fermentation techniques and the same bacterial species that are already used in the dairy industry that is often taken as the reference. Although it was not possible to obtain a nutritional profile superior or identical to pure milk yoghurts, products made this way show however an interesting nutritional profile (ref ?). This may depend on the species and even the strain used for the fermentation which also could affect in turn the sensory profile of the product, removing the undesirable "beany" flavor to a much creamy sensation. However, little is known about fermentation of mixes between animal and vegetal products yet, (Ben Harb et al 2019). Therefore, there is room for investigation and this review gives clues about legumes and their properties and how it is possible to use them in order to design novel food. In that way both affordable and sustainable, mixes could offer an interesting response to the current demand of proteins, in order to nourish an always growing population.

Figure 1 :

 1 Figure 1: Behavior of the pea proteins at the oil-water interface in a sequence of (1) migration, (2) adhesion, (3) partial denaturation and reorientation, and (4) formation of a viscoelastic film at the interface (Burger et Zhang 2019).In red there are hydrophobic patches on the protein surface that promote the adsorption.

  [START_REF] Kaur | Characterization of protein isolates from different Indian chickpea (Cicer arietinum L.) cultivars[END_REF][START_REF] Ma | Thermal processing effects on the functional properties and microstructure of lentil, chickpea, and pea flours[END_REF][START_REF] Ben-Harb | The rheological and microstructural properties of pea, milk, mixed pea/milk gels and gelled emulsions designed by thermal, acid, and enzyme treatments[END_REF]). In pea gels, the addition of vegetal fats like rapeseed oil increases G'. When gels incorporate emulsion droplets, the presence of emulsifying proteins at the droplets' interface helps connecting them as active fillers inside the gel's structure (Ben-Harb et al. 2018).

Table 1 :

 1 proximate nutritional composition of cow milk, egg and several legumes. .... 7

Table 2 :

 2 Overview of the key components and their nutritional or rheological properties. .................................................................................................................................. 8

	Figure

Table 3 :

 3 ........................................................ 12 Comparison of essential AA amounts in animal and vegetal products with basic human needs ............................................................................................................................. 17

Table 1 :

 1 Overall nutritional composition of cow milk, egg and several legumes.

	Composition (g
	Ingredient

/100g) Energy (kcal/100g) Water Proteins Carbohydrates Fats Fibres

	Cow milk	45.8	89.7	3.28	4.8	1.53	0
	(semi-skimmed)
	Egg white (raw)	48.1	87.6	10.8	0.85	0.19	0
	Egg yolk (raw)	307	55	15.5	1.09	26.7	0
	Pea, Pisum sativum	344	8.33	22.8	52	1.44 15.58
	(split pea, dry)
	Chickpea, Cicer	351	8.99	20.5	47.5	5.85	13.3
	arietum
	(raw seed, dry)
	Soy, Glycine max	419	7.77	34.5	20.8	19.2	13
	(raw seed)
	Lupine, Lupinus albus	356	10.4	36.2	21.5	9.74	18.9
	(raw seed)

Reference : (« Ciqual

Table de composition nutritionnelle des aliments » s. d.)

Table 2 :

 2 Overview of the key components and their nutritional or rheological properties.

	Ingredient	Component Name	Functional properties	Nutritional properties	References
			Proteins
	S	Glycinin (11S)	Aggregating Gelling Emulsifying	N.A	(A. Grygorczyk et Corredig 2013; Roesch et al. 2004; Malaki Nik et al. 2009; Lin, Hill, et Corredig 2012)
	O				(Benjamin et al. 2014)
	Y	β-Conglycinin (7S)	Aggregating Gelling Emulsifying	N.A	(Roesch et al. 2004; Malaki Nik et al. 2009; Benjamin et al. 2014; Lin, Hill, et
					Corredig 2012)
		Legumin (11S)	Emulsifying Aggregating Gelling	Hypoallergenic	(Benjamin et al. 2014; Boye, Zare, et Pletch 2010; Amagliani et Schmitt
	P		Salt soluble		2017; Ben-Harb et al. 2018)
	E A	Vicilin (7S)	Emulsifying Aggregating Gelling Salt	Hypoallergenic	(Benjamin et al. 2014; Boye, Zare, et Pletch 2010; Amagliani et Schmitt
			soluble		2017; Ben-Harb et al. 2018)
		Convicilin (7S)	Gelling	N.A	(Ben-Harb et al. 2018)
		α-Conglutin (11S)	Emulsifying	N.A	(Kohajdová, Karovičová, et Schmidt 2011)
	LUPINE
		β-Conglutin (7S)	Emulsifying	N.A	(Kohajdová, Karovičová, et Schmidt 2011)

  ;

	M	Squalene	Foaming Emulsifying Emulsifying	Anti-oxidant	Corredig 2013; Boye, Zare, et Pletch 2010) (Kalogeropoulos et al. 2010; Kim et al. 2017)
	I L K L E G U	Albumin β-Lactoglobulin Raffinose Stachyose	High Solubility Carbohydrates in water Foaming Emulsifying Gelling Foaming N.A N.A	Low digestibility Antihypertensive, antioxidant, Gases, growth-promoting effect on bifidobacteria antimicrobial, rich in essential amino-acids Gases, growth-promoting effect on	(Boye, Zare, et Pletch 2010; Ghumman, Kaur, et Singh 2016) (Benjamin et al. (A. Grygorczyk et Corredig 2013; Olson et al. 1981; Mitsuoka 1982) 2014; Amagliani et Schmitt 2017; Sharma 2019; Destribats et al. 2014) (A. Grygorczyk et Corredig 2013; Olson et al. 1981; Mitsuoka 1982)
	M		Gelling,	N.A bifidobacteria
	E S	Ovalbumin Lactose	Aggregating Foaming Gelling, N.A	lower the risk of Iron transport Intolerance, low-absorption,	(Mine 1995) (Ismail 2016; Favier et Dorsainvil 1985)
		Ovotransferrin	Aggregating	diabetes	(Mine 1995)
			Foaming
			Others
			Gelling,	N.A
	E SOY	Ovomucoid Isoflavones	Aggregating Foaming N.A	Lower the hormonal	(Mine 1995) (Jiang, Cai, et Xu 2013)
	G			disease risk
			Gelling,	N.A
	G	Ovomucin	Aggregating		(Mine 1995)
			Foaming
			Gelling,	antimicrobial
		Lysozyme	Aggregating		(Mine 1995)
			Foaming
		Globulin (white egg)	Gelling Foaming Aggregating	N.A	(Mine 1995)
			Fats
	L E	Phytosterols	N.A	density Protection against low	(Kalogeropoulos et al. 2010)
	G			lipoprotein
	U			oxidation, anti-oxidant, anti-
	M			inflammatory
	E
	S
					Alexandra
					Grygorczyk,
					Alexander, et

  al. 2014; Amagliani et Schmitt 2017; Destribats et al. 2014). Furthermore, they easily form a protective layer around the droplets, preventing coalescence (Ghumman, Kaur, et Singh 2016; Amagliani et Schmitt 2017).

Table 3 :

 3 Comparison of essential AA amounts in animal and vegetal products with basic human needs

Amount of essential AA (in % of a 70kg adult need)

	Soy,
	Glycine max	121% 121% 52% 129% 236% 104% 168% 211% 157%	6
	(raw seed)
	Lupine,
	Lupinus albus (raw	82% 100% 24% 92% 115% 77% 127% 103% 147%	7
	seed)
	Needs for
	a adult (in 70kg	1750	2730 1050 2100 1400 1960	1050 280	700	10
	mg/day)
	Phe: phenylalanine ; Leu : Leucine ; Met : Methionine ; Lys : Lysine ; Ile : Isoleucine ; Val : Valine ; Thr : Threonine ; Try :
	tryptophan ; His : Histidine. (1) (Favier et Dorsainvil 1985) ; (2-9) (« USDA » s. d.) ; (10) (Joint Expert Consultation on Protein and Amino
	Acid Requirements in Human Nutrition et al. 2007). Three color gradient scale: 0% = red ; 50% = yellow ; 100% = green
		Phe	Leu	Met Lys	ILe	Val	Thr	Try	His	Ref.
	Cow milk
	(semi-	10%	13%	8%	12% 15%	12%	14% 16% 13%	1
	skimmed)
	Egg white (raw)	7%	37% 38% 38% 47%	41%	43% 45% 41%	2
	Egg yolk (raw)	39%	51% 36% 58% 62%	48%	65% 63% 59%	3
	Pea,
	Pisum
	sativum	66%	62% 19% 84% 70%	53%	77% 57% 84%	4
	(split pea,
	raw)
	Chickpea,
	Cicer
	arietum	63%	54% 26% 66% 63%	44%	73% 71% 81%	5
	(raw seed,
	dry)

Acknowledgements

I would first of all like to thank Mrs Valérie GAGNAIRE and Mrs Fanny GUYOMARC'H for their confidence in the achievement of this work. I particularly welcome their support in the search for bibliographical references and their assistance throughout the duration of this project, with the hope that the information provided in this synthesis will be useful to them in their research work.


Gaelle Arvisenet

Valérie Gagnaire

A dairy non-dairy mixed product to help the transition towards a plantbased diet?

Introduction

The overall demand for animal protein sources such as meat, milk, and eggs is increasing fast, driven by the growing populations and rising incomes [START_REF] Steinfeld | Livestock's long shadow: environmental issues and options[END_REF]. Meat-based and dairy products are the main protein sources in the human diet [START_REF] Henchion | Future Protein Supply and Demand: Strategies and Factors Influencing a Sustainable Equilibrium[END_REF].

However, livestock farming and activities affect the environment in an important way and are responsible for the production of greenhouse gases and other pollutants contributing significantly to climate change. Besides, meat and animal product consumption has substantial effects on long-term health [START_REF] Godfray | Meat consumption, health, and the environment[END_REF]. Therefore, it is needed to feed the growing population with more sustainable food, and dietary changes towards more sustainable food habits may be attractive for both public health and environmental perspectives.

Meat products consumption per capita is not foreseen to increase a lot in the next coming years [START_REF] Alexandratos | World agriculture towards 2030/2050: the 2012 revision[END_REF]. However, animal protein intake is commonly recommended to be reduced in favor of vegetable proteins that are known to have better health effects and lower environmental impacts [START_REF] Rizkalla | Health benefits of low glycaemic index foods, such as pulses, in diabetic patients and healthy individuals[END_REF][START_REF] Stehfest | Climate benefits changing diet[END_REF]. [START_REF] Elzerman | Consumer acceptance and appropriateness of meat substitutes in a meal context[END_REF] and many other authors have focused on plant-based meat substitutes acceptance of consumers and it also exists many of these products on the market as well as plant milk and vegan cheese. The non-dairy products market is growing fast, however dairy products consumption remains high. Therefore, it is needed to understand consumer's attitudes towards non-dairy products in order to create new products that could help the transition towards more sustainable diets. what could be a potential product that would help consumers to decrease their dairy products consumption in a way that wouldn't force them to change but help them to do it by themselves.

1

Transition towards a more plant-based diet

Meat-based and dairy products are commonly consumed and are the main sources of protein in modern societies. However, there is a growing public concern about the adverse effects of their consumption on health and environment as well as animal welfare and slaughtering among others [START_REF] Niva | Barriers to Increasing Plant Protein Consumption in Western Populations[END_REF]. Therefore, some consumers try to tend to reduce their meat product consumption to increase their plant-based product intake.

Intention to change

To help people throughout the transition to a generally more sustainable diet, it is a priority to know to what extent people are ready and willing to replace animal proteins with plant ones.

There are some indications showing a growing interest and acceptance of plant-based protein and there is an increasing number of recipes for vegetarian and vegan dishes. Consumers tend to think that vegan food is better for health [START_REF] Brückner-Gühmann | Enrichment of yoghurt with oat protein fractions: Structure formation, textural properties and sensory evaluation[END_REF].

Familiarity plays an important role in consumer's acceptance of plant products and their frequent consumption that is likely to increase in people that already consume them [START_REF] Vainio | From beef to beans: Eating motives and the replacement of animal proteins with plant proteins among Finnish consumers[END_REF]. In a study 2011, Elzerman and colleagues have shown that consumers' acceptance of substitutes based on soy protein were influenced by their evaluation of how much the substitute looks compared to the regular one.

People that are undergoing a dietary change towards more plant proteins show more natural concerns, health social image and price than people that are already in a diet that includes plant products. Moreover, natural concerns, health, and weight control motives are important for adopting and maintaining more sustainable diets [START_REF] Vainio | From beef to beans: Eating motives and the replacement of animal proteins with plant proteins among Finnish consumers[END_REF].

In their review of 2017, Niva and colleagues deal with the adoption of a new diet that becomes more and more rich in plant proteins. It requires to replace old behaviors with new ones.

Therefore, when it comes to replacing animal products with plant-based ones, consumers become more and more aware of the benefits of replacing meat products and they be will questioning themselves about the role of animal products in their diet as well as they will begin to look for plant-based substitutes in supermarkets for instance. The repetition of those behaviors will make them more automatic and unconscious. Changing one another behavior is therefore the key point in the increasing consumption of new plant-based products that are dependent on consumers' motivations to do it.

Despite growing motivations to move towards more sustainable diets, plant protein consumption remains stable [START_REF] De Boer | Protein consumption and sustainability: diet diversity in EU-15[END_REF]. Therefore, some barriers to increased plant-based protein consumption still exist.

Barriers

Here, we are dealing with the issues making people complicated to increase their plant product intake and lower their animal product consumption. The most important factor that influences consumers' acceptability of new food is sensory characteristics. Those characteristics are taste, texture, appearance, and odor. They are distinct between plant-based and meat products, explaining the difference between their acceptability and may be a barrier to increase plant protein intake [START_REF] Niva | Barriers to Increasing Plant Protein Consumption in Western Populations[END_REF].

Evidence has been found that convenience and price motives are barriers to animal products substitution with plant-based ones, and more generally in climate-friendly food choices, especially in people that usually consume meat products [START_REF] Vainio | From beef to beans: Eating motives and the replacement of animal proteins with plant proteins among Finnish consumers[END_REF].

Concerning environmental and ethical issues, not all the consumers know very well the link between global warming and livestock herding and people that are skeptical about climate change are less willing to reduce their meat-eating. Moreover, consumers consider that buying local food and consume seasonal fruits and vegetables is more efficient in reducing the carbon footprint than reducing their animal product consumption [START_REF] De Boer | Help the climate, change your diet: a crosssectional study on how to involve consumers in a transition to a low-carbon society[END_REF].

The phenomenon called neophobia could also be an important point regarding the acceptance of a new product. Indeed, when it comes to trying new food, consumers may reject it just because they are not familiar with it and may even expect it to have a bad taste. Therefore, advertising in plant-based substitutes is a major key point [START_REF] Jeske | Past, present and future: The strength of plantbased dairy substitutes based on gluten-free raw materials[END_REF].

Dairy products alternatives

Dairy products are a considerable part of the human diet for thousands of years and provide important nutrients, such as calcium and proteins, that are difficult to obtain in a dairyfree diet. They are also part of the dietary recommendations in many countries [START_REF] Rozenberg | Effects of Dairy Products Consumption on Health: Benefits and Beliefs-A Commentary from the Belgian Bone Club and the European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases[END_REF]. Nonetheless, there is a growing demand for dairy products alternatives, from both consumers and companies, driven by the rising milk allergies, lactose intolerance as well as environmental and ethical issues [START_REF] Haas | Cow Milk versus Plant-Based Milk Substitutes: A Comparison of Product Image and Motivational Structure of Consumption[END_REF].

Plant-based milk is a water extract of legumes, cereals or seeds [START_REF] Kim | Reduction of Bacillus cereus spores in sikhye, a traditional Korean rice beverage, by modified tyndallization processes with and without carbon dioxide injection[END_REF].

Cow milk is more and more decried due to its environmental, health and ethicals considerations.

Still, the product image of cow milk is better than the plant-based milk one.

In a 2019 review, Haas et al. deal with consumers' attitudes towards cow versus plant milk.

The main highlights were that cow milk was perceived as a good source of nutrients with a good taste, convenient to use and with good sensory quality as well as its protein and calcium content.

It was better evaluated than soy milk regarding its taste. The negatives perceptions were concerning the high cholesterol content.

Despite that, plant milk was attributed as naturally sweetened, and being lactose-free was reported as important. It has been reported that consumers find the switching to plant product diet was done because of a lifestyle change such as lactose intolerance or going to a vegetarian diet.

In a study with soy-milk yogourt, the overall acceptance was lower than in regular dairy yogourt whereas it was higher when respondents believed that it was good for their health [START_REF] Wu | Attitudes and acceptability of soy-based yogurt[END_REF].

One way to introduce unfamiliar foods is to combine them with existing foods (Wansink, 2002).

As a result, combining new products like non-dairy products with already existing and well known and used products. Therefore, the idea of a product mixed of both regular dairy yogourt with added plant protein gel making a homogeneous final product in which consumers would find what they like and what they already know and are used to would help them to move toward a more plant-based diet.

Product mixing animal and plant proteins to help the transition?

Nowadays, supermarkets already sell a variety of products marketed as dairy substitutes such as plant milks and yogourts, made of soy, oat, almond, among others. The market for plantbased substitutes is of interest but it needs to progress.

Consumers expectations

The reduction -and also the replacement -of dairy products by plant-based substitutes is an interesting option that is only realistic when consumers accept these new products. Consumers expect plant-based substitutes to be similar as the animal product. Thus, they expect to find as similar as possible dairy substitutes that mimic dairy products.

For instance, consumers' acceptance of meat substitutes requires that they can recognize it as a product that should be eaten instead of meat and that 'form and usage should not be too different from meat' [START_REF] Elzerman | Consumer acceptance and appropriateness of meat substitutes in a meal context[END_REF]. Moreover, everyday products purchase is driven by price, quality, and convenience [START_REF] Bucic | Ethical Consumers Among the Millennials: A Cross-National Study[END_REF].

The overall liking of gels (that can serve as a plant-based yogurt alternative) is mainly related to the sensory attributes: sweetness, moisture, softness, and smoothness [START_REF] Brückner-Gühmann | Enrichment of yoghurt with oat protein fractions: Structure formation, textural properties and sensory evaluation[END_REF]. As a result, for dairy products substitutes such as plant yogurt, consumers want new products like gels that keep the same organoleptic qualities such as taste, texture, odor. Therefore, to fit as much as possible to consumers' expectations, marketers should sell products that are very familiar to them.

As previously seen, price is a key point in the substitution of animal products to plant-based ones. Hence consumers' expectations regarding the price of a new kind of product should not differ too much with the price of the already existing dairy products.

Target consumers

The market for plant-based dairy products is gaining popularity and developing fast.

However, even if the targeted consumers are every one of them, it seems that most of them feel like they are not concerned and those kinds of products are mostly for vegetarians or people allergic to dairy products.

Consumers that have positive attitudes towards sustainable consumption claim to pay attention to the packaging, the origin of the food, the presence of GMOs and are concerned by purchase organic food [START_REF] Vermeir | Sustainable Food Consumption: Exploring the Consumer "Attitude -Behavioral Intention" Gap[END_REF]. As a result, one of the major key points for a product to be attractive for potential consumers will be the packaging and the claims. The major work to be done by marketers to sell new unknown products will be advertising.

Moreover, a good approach of plant as an ingredient in a non-dairy yogurt would be to appreciate its taste. Indeed, would consumers expect a certain plant-based yogurt without the taste of the plant? As a result, industries must also find potential candidates with a good taste to be included in a yogurt not only as a way to make it plant-based or only as a matrix, but also to make it as an added value, as a marketing argument.

New plant protein source

Soy is still the most commonly consumed plant protein source. However, trends show that the market will change due to soy unsustainable concerns such as farming, protein content, allergens, and nutrition and that other plants are trending, making the variety of plant proteins growing.

Lupine is a new plant to be explored, showing good qualities due to its high protein, dietary fibre, and antioxidants contents [START_REF] Fasolin | Emergent food proteins -Towards sustainability, health and innovation[END_REF]. Lupine shows the same characteristics as soy but without some disadvantages. It is rich in protein, does not contain allergens and has a less strong taste that is often blamed in soy. Concerning environmental points, it is cultivated in Europe. Thus, the carbon footprint is lower compared to soy that is most of the time produced in on consumers before thinking about its use as a plant protein.

Conclusion

This review aimed to evaluate the potentiality of a new product on the dairy substitutes market. This is a fast-growing topic and the demand does not stop to increase. This review showed that understanding consumers' attitudes and expectations for a new product is the key point to lead to its success. Therefore, it is needed now to work on the consumer's wanting and beliefs about a potential mixed product that may help them to consume more plant proteins and to reduce their animal protein intake but also to work on information effect and claims on their attitudes towards it.

  The aim of this literature review is, first, to figure out what are the leading factors towards a more sustainable diet that would be more plant-based and also what are the main barriers to achieve it. Then, as a second part, figure out what are the consumers' attitudes towards non-dairy products already existing. Finally, this will lead to a third and last part that tries to figure out