Raffaela Piccinelli
email: piccinelli@inran.it

Marchela Pandelova

Cinzia Le Donne

Marika Ferrari

Karl-Werner Schramm

Catherine Leclercq

R Piccinelliª

C Le Donneª

M Ferrariª

K.-W Schramm

Leclercqª

Design and

Keywords: Hormones, Food contact materials, Metals, Pesticide residues Food Types: Baby food, Infant formulae Market basket, baby foods, infant formulae, contaminants, EU 23

Commercial food products specifically designed for infants (0-12 months) are available 2 on the market in all EU countries. Their composition is regulated by two specific directives 3 related to "infant formulae and follow-on formulae" (European Commission 2006a) and to 4 "cereal-based foods and baby foods for infants and young children" (European Commission 5 2006b). In the present paper the terms "Infant formulae and follow-on formulae" and "Other 6 baby foods" (including all others solid and liquid commercial products designed for infants) are 7 used to refer to these two groups of products. According to the legislation, "Infant formulae" 8 (sometimes called "starting formulae") are used during the first months of life and satisfying by 9 themselves the nutritional requirements of such infants until the introduction of appropriate 10 complementary feeding", whereas "follow-on formulae" are used by infants when appropriate 11 complementary feeding is introduced" (European Commission 2006a).

12

The lifestyles changes encourage an increasing number of women to work while their 13 children are young and parents have generally little time to prepare home-cooked foods for 14 infants. This factor, together with manufacturer's innovation, probably contributed to the baby 15 foods market growth which was observed in recent years (Research and Market 2006 [internet]).

16

No more than 35% of infants worldwide are exclusively breastfed during the first four months 17 of life (WHO 2003).

18 Therefore, in order to assess dietary exposure to potentially toxic substances in infants, it 19 appears crucial to monitor their exposure through "Infant formulae and follow-on formulae" and 20 "Other baby foods".

21

Infants are especially vulnerable to the acute, sub-acute and chronic effects of ingestion 22 of chemical hazards. The nervous, reproductive, digestive, respiratory and immune systems of 23 infants are developing.

24

Moreover, dietary exposure of infants to chemical hazards tends to be higher than that of 25 other population groups. In fact, the average energy requirement of an infant aged 0 to 9 months 26 ranges from 0.40 to 0.48 MJ /kg body weight i.e. three times that of a sedentary adult aged 30-27 59 years which is 0.14 MJ/kg bw in males (10.7 MJ for 75 kg) and 0.13 MJ/kg bw in females 28 (8.3 MJ for 62 kg) (Commission of the European Communities 1993). Therefore, when the 29 concentration of a chemical is similar in the diet of infants and adults, the dietary exposure of 30 infants is three times that of adults.

31

In the EU legislation on "Infant formulae and follow-on formulae" and "Other baby 32 foods" there are specific provisions about hygiene, use of food additives, presence of some 33 contaminants and on the use of materials intended to come into contact with foods. These Within the frame of the EU funded project CASCADE ("Chemicals as contaminants in 5 the food chain"; project website: www.cascadenet.org) a specific integrated study called 6 "Babyfood" was performed. The main objective of this study was to provide information on 7 dietary exposure through baby foods to a limited number of endocrine disruptors in the EU. The 8 target substances were bisphenol A (BPA), vinclozolin, polychlorinated dibenzo-p-dioxins and 9 dibenzofurans (PCDD/F), polychlorinated biphenyls (PCB), genistein, procimidone, iprodione 10 and cadmium.

11

The technique recommended by WHO (GEMS/Food 2005 [internet]) to assess dietary 12 exposure to contaminants is the analytical determination of market baskets; this technique is 13 very often used. The extreme case of an infant diet with the exclusive consumption of 14 commercial products is not desirable since breast milk is the preferred food for infants.

15

However, it provides a worst case for the assessment of potential exposure of children to food 16 chemicals contained in these products. 17

The aim of the present paper is to illustrate the methods used within the CASCADE 18 project for the preparation of market baskets of commercial baby foods representing the average 19 diet of infants (aged 0-9 months) who are not breast fed at all and are fed with commercial baby 20 foods only.

22

Materials and Methods

23

Market basket design and sample collection

24

In order to sample the food products, EU market baskets were created to represent the diet for 25 each of the first 9 months of life of an infant who is not breast fed at all and is fed with 26 commercial baby foods only. Such baskets, that aim to assess the average dietary exposure of 27 infants in the EU, may not capture information on the variability of such exposure. Therefore, 28 additional National market baskets were designed in order to assess the geographical variability.

29

Four countries were selected: Sweden, Italy, Spain and Slovak Republic.

30

To design the baskets, "Infant formulae and follow-on formulae" and "Other baby foods" 31 products were considered separately and monthly-based diets were elaborated. In the first group 32 of products "Infant formulae" and "follow-on formulae" were considered. Both typologies were formulae" and "Other baby foods", were purchased from the Company "Food for Thought" 12 (FFT) ([Internet]). For each block of products taken separately, the overall market share of each 13 Holding Company in the 22 countries was taken to represent its market share for these products 14 in the whole EU. For the 4 specific countries, the national market share was used. These data 15 were used to identify the brands of the products to be sampled. The name of the Holding 16

Companies and of their main brands in 22 EU countries was obtained together with their overall 17 market share.

18

The company FFT was able to provide data for three blocks of products:

19

-Baby milks: including the 6 categories of baby milks to be sampled ("infant formulae" and 20 "follow-on" of milk formula, soy formula and hypoallergenic formula respectively).

21

-Baby Jars including: baby food canned, in bottles or in jars, excluding freeze dried products.

22

-Other Baby Foods including: juices and all dried products such as cereal powders with and 23 without milk, biscuits, dry pasta and any freeze-dried product such as freeze dried meat, 24 freeze dried fish, herbal tea.

25

The overall market shares for each of these three blocks of products were used as proxy 26 for the specific market shares of the specific products belonging to them.

27

Products belonging to the last two blocks, "Baby Jars" and "Other Baby Foods" are called 28 in this paper "Other baby foods". They include all liquid and solid commercial baby foods with 29 the exclusion of "Infant formulae and follow-on formulae".

30

To identify the products and to design the market baskets, different methods have been 31 followed depending on the category of products ("Infant formulae and follow-on formulae" or 32 "Other baby foods") and the typology of the sample (EU or National).

33

Holding Companies were ranked in decreasing order of market shares and the first 34 companies that cumulatively reached over 80% were selected. hereafter "leading companies". A check of the websites of these companies showed that they 1 produce and distribute the same (or similar) products in most EU countries. For logistic reasons, 2 the collection of products was therefore tentatively organised in a unique country. Germany was 3 selected. Consequently, the brands of the leading companies that were on the German market 4 were identified. In all cases where a leading company did not have a brand in Germany, an 5 alternative country was selected in which a brand of the same leading company was present.

6

Therefore only a part of products were bought in Germany. The criterion used for the selection 7 of the alternative country was "being the country with the highest estimated number of potential 8 consumers within EU". Demographic data were downloaded from EUROSTAT (2009) 9 ([Internet]) to assess the dimension of the population aged less than 1 year in each of the 22 EU 10 countries. The number of potential consumers was estimated by weighing these data with the 11 market shares of the leading company of interest in each of the 22 countries. 12 13 Regarding the National baskets, in order to capture the highest variability in chemical 14 content of the diet, only one brand was identified in each of the four selected countries. It was 15 the main brand from the leading company with the highest market share in that country. If 16 certain categories of product were not produced by this leading company in that particular 17 country, the most popular product (from another Company) sold in the same category was 18 identified. This identification was performed through expert judgement. In order to find the name of all "Infant formulae and follow-on formulae" products of the brands 22 identified, the websites of the brands were searched or the leading companies were contacted.

23

In term to EU baskets of "Infant formulae and follow-on formulae" the percentage of 24 each product was simply the proportion of market share of each brand among the leading 25 companies. In the event that more than one product was available for one brand, the market 26 share of the specific brand was equally divided by the number of products.

27

For the National baskets, each typology of product was represented by a unique brand in 28 each of the 4 selected countries and 100 was the percentage of each brand.

31

The name of the "Other baby foods" products were identified with the help of some CASCADE 32 partners who searched products on their own country market. In order to find the names of the 33 products to be sampled they were suggested to contact a Chemist's who would provide them a 34 list of all products for the brand of interest or to search the websites of the companies or to

6

The following steps were followed to generate the baskets: (FAO 2004) for formula-fed infants were used to 12 calculate the average energy requirements (kcal/day) of infants in the first 9 months of 13 life (Table 1). For the reasons above explained, month 5 was chosen to insert little 14 quantities of complementary foods. It was observed that the average energy intakes 15 assessed by SCF (2003) from the 5 th to the 7 th months of age for infants fed with both 16 complementary foods and follow-on formula were slightly higher than the energy 17 requirements calculated from FAO (2004) and WHO (2006) (Table 1). Also average 18 body weights were slightly higher. Therefore, in table 1, for infants of 5 th months of 19 age, the energy requirement for 5-6 month (622 kcal/day) was considered instead of that 20 for 4-5 month (598 kcal/day). The same substitution was also applied for months 6 th to 21 9 th .

22

(Table 1here) schedule, used in the design of the market baskets, the food category "infant cereals" 1 was divided into "infant cereals without gluten", "infant cereals with gluten" and 2 "infant cereals with milk" and the food category "fruit" was split into "pureed fruit" and 3 "fruit juice". Eggs were not present in commercial baby foods for infants aged up to 9 4 months and therefore not considered in the final schedule. This is due to the caution 5 required in the introduction of whole eggs due to the allergy risk (Michaelsen et al. 6 2003). Moreover several brands of baby foods were found to distribute "dairy based 7 dessert with chocolate" that can be consumed by infants aged 6 to 9 months. The results 8 of the food consumption survey performed in UK (Mills et al. 1992) suggest that these 9 typologies of baby foods are effectively consumed in this period of the life. These 10 products were therefore also included in the 9 th month basket and the food category 11 "dairy based dessert" was divided into "dairy based dessert with fruit" and "dairy based 12 dessert with chocolate".

13

(Figure 1 16 Amounts, energy and nutrient content of "follow-on formulae" and "Other baby 17 foods": the estimated average amount of "follow-on formulae" consumed by 18 infants during the 5 th , 6t h and 7 th month (respectively 600 ml/day, 400 ml/day and 19 240 ml /day) were taken from a report of Scientific Committee on Food (SCF 20 2003). These amounts of liquid "follow-on formulae" (ml/day) were translated in 21 gram/day of powder, according to the label of the sampled products, that suggests 22 to use on average 30 ml of water to dilute 4.6 g of powder of "follow-on formulae" 23 and based on an estimated volumetric density of milk of 1.03 g/ml (Di Thomas, 24 2003). The daily energy intake from "follow-on formulae" was calculated based on 25 its average energy content according to the labels of the products of 8 brands (70.8 26 kcal/100 g). The daily energy intake from "Other baby foods" was then calculated 27 by difference (Table 1).

29

To calculate the nutrient content of the elaborated diets, the average of values (by 30 typologies of product) reported on labels of 6 brands among the most popular in 31 EU was assessed.

32

The monthly diets were elaborated in three steps: "infant cereals" products. The amount of this latter category was calculated by 3 difference from the total calculated energy intake from "Other baby foods" (Table 4 1). 5

2) in terms of typologies of foods products on the basis of specific features of the 6 products (as Infant cereals without milk and with gluten, Infant cereals with milk,

7

Pureed fruit, Fruit juice, Pulses with vegetables, Fish with vegetables etc...): the 8 typologies of "Other baby foods" products to be included in the diets were chosen 9 based on prepared by the CASCADE partner database. Table 2 shows the 10 typologies of products and the specific features selected for inclusion in the EU 11 baskets.

12

The selection was based on the availability of similar products in different EU 13 countries. Added fats (oil, butter, etc….) were not sampled, since they were 14 present as ingredients in the mixed baby dishes and no such products specifically 15 designed for babies were available in any EU country.

16

Table 3 shows the elaborated monthly diets infants from 5 to 9 months of age (in 17 terms of main category and typology of food products).

18

For the National baskets of the 4 selected countries, the same typologies of 19 products were chosen. If some typologies of products were not available in 20 certain countries, the basket was modified for this country only. For example the 21 typologies of products "Infant cereals without milk and with gluten", "Dairy 22 based dessert with chocolate", "Biscuits", "Pulses with vegetables and fish" and 23 "Pulses with vegetables and potatoes" were not available in Sweden. These 24 typologies were therefore replaced with "Infant cereals with milk and with 25 gluten" ,"Dairy based dessert with forest fruit", "Infant cereals with milk and 26 with gluten" and "Fish, pulses with vegetables and potatoes", respectively. For 27 similar reasons the National baskets of Slovakia were slightly modified with 28 respect to the standard baskets.

29

(Tables 2 andTable 3 here For each food typology, the products chosen were the same for all ages of the 1 infants; thus pureed fruit was the same at 5 th , 6 th , 7 th , 8 th and 9 th . The National 2 baskets were designed with a unique product from a unique brand.

4

The percentages of energy from proteins and lipids were calculated for the 5 monthly diet elaborated and compared with the WHO recommendations 6 (Michaelsen et al. 2003) for infants aged 5-9 months: 14-14.5 g/day of protein 7 and 30-40% of energy from lipids. 12 was simply the proportion of market share of each of the selected leading company 13 that were found to produce a specific product.

14

With regard to the EU basket, when a typology of product was not available for a 15 certain brand, "0" was assigned as percentage of market share for that leading 16 company and the percentage of the other brands of the same typology were 17 increased proportionally, leading to a "corrected market share" . As far as the 18 National baskets were concerned, also in this case, when the selected "leading 19 company" did not distribute a certain category of product in the country, the most 20 popular product of that category sold in the country was identified for sampling.

22

The preparation of the "Other baby foods" baskets, as they were designed initially and above 23 described, would have required collection and sample preparation of a huge number of products 24 and consequently lead to very high costs in terms of time and budget resources. Therefore, a 25 random sampling of brands, weighed on market share, was performed in order to identify only 26 one brand within each typology of product. For the National baskets of "Other baby foods", 27 only the 5 th month diet was prepared due to lower number products included compared with 28 month 6 th , 7 th , 8 th and 9 th . 29 Table 4 shows an example of EU basket of "Infant formulae and follow-on formulae" and 30 "Other baby foods" at month 5 with the products purchased only (the name of the brands were 31 substituted with a code). The other baskets (with all the products selected and with the products 32 purchased only) are not reported as tables in the present paper due to space restrictions but can 33 be requested to the corresponding author. The pooling of the EU and National basket baby foods samples and related weighting 10 procedures were performed in a purified glovebox under nitrogen atmosphere. Prior to pooling, 11 the solid food and beverages were lyophilisated using the freeze drying equipment Type BETA 12 1-16 (Christ GmbH). Overall, the duration of the procedure for each food item was about 36 13 hours. After lyophilisation, the weight of baby food products was reduced with yield varying 14 from 12 to 22%. The proportion of each "Other baby foods" product in the pooled samples was 15 that reported in Table 4. The samples were homogenised in a rotoshaker, Type Reax 20/8 16 (Heidolph GmbH) for 8 hours at 10 rpm. 17

(

22

The number of baskets and of product sampled is reported in Table 5.

4

As far as National baskets of "Other baby foods" are considered, 4 market baskets were 5 elaborated and 47 products were identified. As already mentioned only the basket for the 5 th 6 months was prepared, based on a total of 13 products.

7

(Table 5 here

2

Another limitation of the market basket illustrated in the present paper is that the market 3 shares of the specific categories of "baby milks", "baby jars" and "other baby foods" were not 4 available. Thus, since no specific market shares were available for "fruit baby jars" the 5 assumption was made that the market shares of "baby jars" in general could apply to "fruit baby 6 jars". Moreover, market share data used to identify the brands of the products to be sampled, did 7 not contain private brands (supermarket) and baby foods of this kind of market were not 8 sampled. However, the market share of each of these private brands is known to be low and they 9 would not have been selected as leading brands. In fact, the overall market share of non 10 identified brands of all the baby foods categories considered was 4.5% including private labels.

11

Since the overall share of such private brands is growing, in future studies one might consider 12 the random extraction of some private brands that would be included in the market basket in 13 proportion to such overall share.

14

The amount of proteins in the monthly diets here elaborated and expressed in terms of 15 typologies of products was higher than recommended by WHO (up to 11% versus 9%) (Table 16 4). However, this percentage of protein is lower than that observed in food consumption surveys 17 performed in infants in some European countries: 13.2% of energy in the UK for infants aged 6-

23

On the other hand, the percentage of energy from fat was slightly lower than 24 recommended (24-35% versus 30-40%), due to the fact that 'added fats' were not considered in 25 the elaboration of the monthly diets.

26

It is likely that some infants can consume honey since birth. This fact was taken in 27 consideration, but this food was not sampled because honey is not distributed by companies of 28 baby foods.

29

The lyophilisation of fruity baby foods in jar result a sticky material that caused 30 difficulties in further homogenisation of the samples. As a consequence, these specific products 31 were delivered separately from the other products belonging to the same basket. The further 32 pooling was therefore performed in each testing laboratory itself according above mentioned During the survey, the labels of infant formulae were checked and it appeared that the 1 total energy intake of infants aged 0-4 months could be higher than recommended when the 2 consumer followed instructions reported on the label. This observation has been reported by 3 Pandelova et al., (2009a).

4

Several samples of "Infant formulae and follow-on formulae" and "Other baby foods", 5 both extracted and non extracted, were prepared and delivered to CASCADE partners for 6 further chemical target analysis, in-vitro and in-vivo testing. The results of some analyses are 7 published (Riu 2008, Pandelova 2009b).

8

The above described samples of baby foods have been used for the assessment of dietary 9 exposure to a number of substances within the CASCADE project, with the aim of obtaining a 10 realistic panorama of exposure to food chemicals in the infant population, useful for quantitative 11 risk assessment.

12 Market basket studies involve the analysis of groups of foods that reflect the average 13 food consumption patterns of a given population. They may be used to establish specific 14 maximum limits when there is evidence that the health of specific consumers may be at stake 15 (CGSCTFF, 1999). In the present study, a market basket was designed to assess exposure in a 16 very sensible population group: infants. 17

Given the time and resources available it was decided to distinguish only two groups of 18 foods: "infant formulae and follow-on formulae" and "other products" and to focus on possible 19 variability at the different ages of the babies and between countries rather than on variability 20 between products categories. Thus, if a food chemical was to be found at a high level of 21 concentration in one or more of the designed baskets it may not be possible to identify the 22 incriminated product category. However, products were purchased in excess so that further 23 analyses on single categories can be performed afterwards.

24

Despite some limitations, the method should allow to assess average dietary exposure of (1) The theoretical diets were designed in order to ensure that the energy intake from "Infant formulae and follow-on formulae" and from "Other baby foods" were in line with those reported in table 2. (2) In parenthesis consumption of "Infant formulae" expressed in ml/day of product ready to be consumed.

(3) The amount of this food category was calculated by difference from the calculated energy intake from "Other baby foods" (Table 3). ( 4) "Added fats (oil/butter etc..)" were not sampled, since they are present in commercial baby foods mixed dishes and no such products specifically designed for babies were found to be available in any EU country. (5) The total quantity of jars containing meat was calculated to ensure the daily consumption of the portion size of meat considered in the theoretical diets elaborated in terms of main food categories. (1) The theoretical diets were designed in order to ensure that the energy intake from "Infant formulae and follow-on formulae" and from "Other baby foods" were in line with those reported in table 2. (2) In parenthesis consumption of "Infant formulae" expressed in ml/day of product ready to be consumed.

(3) The amount of this food category was calculated by difference from the calculated energy intake from "Other baby foods" (Table 3). ( 4) "Added fats (oil/butter etc..)" were not sampled, since they are present in commercial baby foods mixed dishes and no such products specifically designed for babies were found to be available in any EU country. (5) The total quantity of jars containing meat was calculated to ensure the daily consumption of the portion size of meat considered in the theoretical diets elaborated in terms of main food categories. (1) The theoretical diets were designed in order to ensure that the energy intake from "Infant formulae and follow-on formulae" and from "Other baby foods" were in line with those reported in table 2. (2) In parenthesis consumption of "Infant formulae" expressed in ml/day of product ready to be consumed.

(3) The amount of this food category was calculated by difference from the calculated energy intake from "Other baby foods" (Table 3). ( 4) "Added fats (oil/butter etc..)" were not sampled, since they are present in commercial baby foods mixed dishes and no such products specifically designed for babies were found to be available in any EU country. (5) The total quantity of jars containing meat was calculated to ensure the daily consumption of the portion size of meat considered in the theoretical diets elaborated in terms of main food categories. (1) Data referred to 2007, purchased from the Company "Food for Thought" (FFT) (http://www.fft.com/fftt/servlet/fftt/template/Index.vm).

(2) In the event that more than one product was available for one brand, the percentage of each brand was equally divided by the number of products.

(3) Meat jars of the sampled company do not contein vegetables. As a consequence the typologies "meat + vegetables +potatoes" was obtained by combining meat jars and vegetables jars.

  to reduce the potential dietary exposure of infants to a number of 1 microbiological and chemical hazards.2However there are no provisions in relation to a number of important endocrine disruptors 3 (with the exception of provisions for pesticides).

  4

  33 represented with three kinds of "Infant formulae and follow-on formulae": milk based formula, 34 soy based formula and hypoallergenic formula, for a total of 6 kinds of products. The baskets 35 introduction in the diet of "Other baby foods" from 5 months of age of 1 an average infant weaned with commercial baby foods only. In the EU, some infants already 2 receive little quantities of complementary foods at 4 months but the majority of infants receive 3 such foods after 6 months of age, as suggested by World Health Organization (Michaelsen K et 4 al. 2003). Moreover a recent opinion by EFSA (2009) states that the introduction of 5 complementary food into the diet of healthy term infants in the EU between the age of 4 and 6 6 months is safe and does not pose a risk for adverse health effects. Month 5 was therefore 7 chosen to represent the average between fourth and sixth month. From month 5 to month 9 the 8 baskets of "Other baby foods" were varied every month with the addition of new "Other baby 9 foods" products. 10 Market share data of year 2007 of 22 single countries, for "Infant formulae and follow-on 11

19 20"

 19 Infant formulae and follow-on formulae" baskets 21

  . An appropriate database, organised by typology of products was filled 1 by CASCADE partners. The original name of each product and its English translation were 2 recorded together with a brief description of the product and some other information (typology 3 of packaging, month of introduction as suggested by the producer, main ingredients, ready to eat 4 or powder ).

7A)•

  Identification and assessment of the elements necessary for the elaboration of the diet for EU 8 and National infants from month 5 to month 9: 9 Calculation of energy requirements: the standard values of weight for age and sex 10 established by WHO (WHO 2006) and the estimated energy requirements (kcal/kg of 11 body weight/day) set by FAO

23 24•

 23 Identification of food categories included in the "Other baby foods" basket for each 25 month of age: in order to establish the month of inclusion of each category of product, 26 the guidelines for infant feeding developed by WHO Europe (Michaelsen K et al. 2003) 27 were considered. However, these guidelines do not provide recommendations at a high 28 level of detail in terms of product categories. The only paediatricians' guidelines 29 providing recommendations at a high level of detail in the European region are those 30 from Switzerland. Therefore, the guidelines of the Swiss Paediatric Society (Société 31 Suisse de Pédiatrie 2002 [Internet]) were used to complement the WHO guidelines.

32

  On these bases, a first theoretical schedule of the monthly inclusion of "Other baby 33 foods" was created. The availability of these products in the EU countries was then 34 investigated in order to produce a refined schedule (Figure1). Thus, in the final 35

  Elaboration of the monthly diets:

33 1 )

 1 in terms of main food categories (as infant cereals, pasta, fruits, meat etc...): the 34 diets were designed in grams for each category of "Other baby foods", based on 35 suggested by producer labelling and on the meal daily frequency 1 suggested byWHO Europe (Michaelsen et al. 2003), with the exception of 2

  terms of specific products identified: the tables filled in by the responsible 32 person for shopping were used to choose the specific products to be inserted in 33 the EU and National baskets, based on their ingredients.

  Creation of the EU and National baskets: 10 Calculation of the percentage of the different products within the sample: the 11 percentage of each brand within the EU and National baskets of "Other baby foods"

8

  4 follow-on formulae" and 55% of "Other baby foods" products) and delivered to Helmholtz 5 Zentrum München. The other products were bought in Germany, where sample preparations 6 were performed prior analyses. 7 Pooling, homogenisation, and lyophilisation of the baby foods samples 9

  The samples were kept at room temperature and stored in brown glass jars protected from 18 direct light. In order to prevent any contamination, each further open and close of the sample 19 collector was performed under nitrogen atmosphere. 20 21 Results

23 24"Page"

 23 Infant formulae and follow-on formulae" baskets25The first 8 leading companies of "Infant formulae and follow-on formulae" in the EU were 26 selected, covering altogether 82% of the entire EU market. A total of 42 products were 27 purchased from 6 different countries in order to prepare 6 EU market baskets of "Infant 28 formulae and follow-on formulae".29On the other hand, 20 products were purchased to prepare 24 National market baskets of 30 "Infant formulae and follow-on formulae". to the baskets of "Other baby foods", the 6 leading companies of the "baby jars" 34 market and the first 7 companies of the "other baby foods" market were selected, covering 35 and 81% of the entire EU market. Nine EU market baskets of 1 Other baby foods" were designed and 112 products were identified. However because of the 2 above mentioned reasons, only 22 randomly extracted products were sampled from 5 different 3 countries.

  consumer exposure to food chemicals are needed for regulatory chemical 12 risk assessment. Among the main approaches to food chemical intake assessment, WHO 13 recommends the development of a diet model or market basket representing the average diet of 14 the considered population. This model may then be analysed directly for food chemicals of 15 interest (WHO 1999). 16 Survey market baskets are generally developed on the basis of national food 17 consumption data. It is the case in the U.S (FDA[Internet]), in Australia (FSANZ [Internet]), 18 and in the UK (MAFF [Internet]). A food consumption survey that could be considered 19 representative at EU level is not available. Moreover, in many EU countries, information on 20 exposure to chemical hazards in the diet is collected for the whole population, not specifically 21 for children or infants. The available information is often incomplete or not comparable between 22 EU countries. In order to assess exposure to hazardous chemicals through food, the data 23 collection needs to be harmonized and data need to be collected regularly and to reflect the 24 specific risks to children and infants in the region (ENHIS 2007). For these reasons the 25 methodologies generally used to elaborate national markets baskets have been adapted to the 26 needs of this study. Baskets were designed on the basis of theoretical schemes of insertion of 27 baby foods and of EU market share data for "Infant formulae and follow-on formulae" and 28 "Other baby foods".29The market share data purchased were expressed in value (money) because baby food 30 data expressed in volume (amount of products) were not available at the same level of 31 disaggregation. Although the price of products of the same typology can be different depending 32 on the brand, one leading company can also produce more than one brand destined to different 33 kinds of market (e.g. only for supermarkets with a low or medium price, only for chemists' with 34 a high price). It was therefore assumed that on average the prices of similar products are 35 companies and data purchased were used as a proxy for market shares in 1 volumes.

  Mills et al 1992 ), 11.2-13.2% of energy in Germany for infants aged 3-9 months 19 (Alexy et al. 1999), 13-14% of energy in Denmark for infants aged 9 h months (Hoppe et al. 20 2004), 13.3-15.7% of energy in Spain for infants aged 4-9 months (Capdevila et al. 1998). The 21 amount of proteins in the diets considered in the present paper are therefore intermediate 22 between that recommended by WHO and that observed in consumption surveys.

  25 infants in the EU. The food items considered for the elaboration of the monthly diets are those 26 normally consumed by this population group, the quantities were set based on nutritional 27 requirements of infants and the products were purchased in seven different EU countries on the 28 basis of EU market share data collected in 22 countries. The technique could be used again in 29 the future and the exposure data obtained through this methodology could support regulatory 30 actions over time and contribute to the promotion of health of infants fed with commercial The authors would like to thank all CASCADE partners for their assistance in the identification, 1 collection and shipping of baby foods namely Ingemar Pongratz, Lars-Arne Haldosen, Stefan 2 Rehnmark, Nicolas Olea, Jean-Pierre Cravedi and Július Brtko. 3 The study was financially supported by the European Union network CASCADE (FOOD-Kersting M, Sichert-Hellert W, Manz F, Schöch G. 1999. Macronutrient intake of 3-10 to 36-month-old German infants and children: results of the DONALD study. Ann Nutr Metab. Vizmanos B, and Martı´-Henneberg C. 1998. Implications of the weaning pattern 14 on macronutrient intake, food volume and energy density in non-breastfed infants during the 15 first year of life. J Am Coll of Nutr. 17( 3): 256-262.

  Figure 1. Time of inclusion of baby food categories: final schedule used in the design of the CASCADE market baskets of "Other baby foods".

Table 4

 4 More than half of the products needed to constitute the EU baskets had to be bought in EU 3 countries other than Germany by the CASCADE partners (57% of "Infant formulae and

	35	here)

Table 1 .

 1 Calculated average energy requirement (kcal/day) by age class in infants aged 0 to 10 months, SCF data from 5 th to 9 th month and calculated daily energy intake from "Infant formulae and follow-on formulae" (follow-on) and "Other baby foods"

	F o r
	P
	e
	e r
	R
	e
	v i e
	w
	O n l
	y

Table 2 .

 2 Categories and typologies of baby foods chosen to design baskets from 5 th and 9 th month.

	FOOD CATEGORY	TYPOLOGY OF FOOD PRODUCTS	SPECIFIC FEATURES OF THE TYPOLOGIES OF PRODUCTS
	INFANT FORMULAE AND	Infant formula follow-on	Infant formula follow on -in powder
	FOLLOW-ON FORMULAE
	INFANT CEREALS:
		Infant cereals without milk and without	Rice -in powder
		gluten
		Infant cereals without milk and with	Multicereals or cereals with gluten-in
		gluten	powder
		Infant cereals with milk	Infant cereals with milk and fruit or
			honey -in powder
	PASTA	Rice or pasta with meat and vegetables	Rice or pasta (around 20%) with meat
			(veal and/or chicken and/or turkey)
			(around 20%) and vegetables (around
			60%) -where available with potatoes -
			in jars (ready to eat)
	BISCUITS	Infant biscuits	Biscuits with gluten -No granular
	FRUIT:
		Pureed fruit	Fruit mix with two fruit among apple
			and/or pear and/or banana and/or
			apricot-in jars (ready to eat)
		Fruit juice	Apricot or other if not available -
			liquid (ready to eat)
	PULSES/VEGETABLES	Pulses with vegetables	Pulses (around 40%) and vegetables
			(around 60%)-where available with
			potatoes -in jars (ready to eat)
	FISH	Fish with vegetables	Fish (sole and/or salmon and/or
			codfish) (around 40%) with vegetables
			(around 60%) -where available with
			potatoes-in jars (ready to eat)
	MEAT	Meat with vegetables	Meat (veal and/or chicken and/or
			turkey) (around 40%) with vegetables
			(around 60%) -where available with
			potatoes -in jars (ready to eat)
	DAIRY BASED DESSERT	Dairy based dessert	Milk or cheese based dessert with
			forest fruit or chocolate -in jars (ready
			to eat)

Table 3 .

 3 Theoretical diets elaborated in terms of main food categories and of typologies of commercial baby foods (months 5-9).

	DIET IN TERMS OF		DIET IN TERMS OF
	MAIN FOOD CATEGORIES		TYPOLOGIES OF FOOD PRODUCTS
	CATEGORIES	Daily consumption (g/day) (1)	Energy (kcal)	TYPOLOGIES	Daily consumption (g/day)	Energy (kcal)
	5 th MONTH
	Infant formulae and follow-on formulae	89 (600) (2)	425	Infant formulae follow-on (powder)	89 (600) (2)	425
	Infant cereals (3)	12	44	Infant cereals without milk and without gluten (powder)	20	74
	Fruit	80	59	Pureed fruit (jar)	80	59
	Vegetables Meat	40 40	19 33	Meat (5) +vegetables +potatoes (jar)	100	63
	Added fats (oil/butter etc..) (4)	5	41
	Total		622	Total		622
	6 th MONTH
	Infant formulae and follow-on formulae	60 (400) (2)	283	Infant formulae follow-on (powder)	60(400) (2)	283
				Infant cereals without milk
	Infant cereals (3)	33	126	and without gluten (powder) Infant cereals without milk	15 15	57 56
				and with gluten (powder)
	Fruit	100	74	Pureed fruit (jar) Fruit juice (liquid)	75 25	56 14
	Vegetables/ Pulses	80	39	Meat (5) +vegetables +potatoes (jar)	200	126
	Meat	80	65	Pulses+vegetables+potatoes (jar)	75	38
	Added fats (oil/butter etc..) (4)	5	41
	Total		630	Total		630

Table 3 (

 3 continued). Theoretical diets elaborated in terms of main food categories and of typologies of commercial baby foods (months 5-9).

	DIET IN TERMS OF		DIET IN TERMS OF
	MAIN FOOD CATEGORIES		TYPOLOGIES OF FOOD PRODUCTS
	CATEGORIES	Daily consumption (g/day) (1)	Energy (kcal)	TYPOLOGIES	Daily consumption (g/day)	Energy (kcal)
	7 th MONTH
	Infant formulae and follow-on formulae	36 (240) (2)	170	Infant formulae follow-on (powder)	36 (240) (2)	170
				Infant cereals without milk and without gluten	10	38
				(powder)
	Infant cereals (3)	27	101	Infant cereals without milk and with gluten	20	75
				(powder)
				Infant cereals with milk and fruit (powder)	10	36
	Fruit	160	118	Pureed fruit (jar) Fruit juice (liquid)	120 40	89 22
	Pasta	20	71	Pasta + meat +vegetables +potatoes (jar)	100	63
	Vegetables/ Pulses	100	49	Pulses +vegetables +potatoes (jar)	75	38
	Meat	80	65	Meat (5) +vegetables +potatoes (jar)	150	95
	Dairy based dessert	40	40	Dairy based dessert (with fruit) (jar)	40	39
	Added fats (oil/butter etc..) (4)	5	41
	Total		656	Total		665
	8 th MONTH
	Infant formulae and follow-on formulae	36 (240) (2)	170	Infant formulae follow-on (powder)	36 (240) (2)	170
				Infant cereals without milk and without gluten	9	33
				(powder)
	Infant cereal (3)	26	99	Infant cereals without milk and with gluten	18	66
				(powder)
				Infant cereals with milk and fruit (powder)	9	32
	Biscuits	8	33	Baby biscuits	8	33
	Fruit	160	118	Pureed fruit (jar) Fruit juice (liquid)	120 40	89 22
	Pasta	20	71	Pasta + meat +vegetables +potatoes (jar)	100	63
	Vegetables/ Pulses	100	49	Pulses + vegetables + Potatoes (jar)	75	38

Table 3 (

 3 continued). Theoretical diets elaborated in terms of main food categories and of typologies of commercial baby foods (months 5-9).

	DIET IN TERMS OF		DIET IN TERMS OF
	MAIN FOOD CATEGORIES		TYPOLOGIES OF FOOD PRODUCTS
	CATEGORIES	Daily consumption (g/day) (1)	Energy (kcal)	TYPOLOGIES	Daily consumption (g/day)	Energy (kcal)
	9 h MONTH
	Infant formulae and follow-on formulae	36 (240) (2)	170	infant formulae follow-on (powder)	36 (240) (2)	170
				Infant cereals without milk and without gluten	8	28
				(powder)
	Infant cereals (3)	22	83	Infant cereals without milk and with gluten (powder)	15	56
				Infant cereals with milk and fruit (powder)	8	27
	Biscuits	8	33	Baby biscuits	8	33
	Fruit	160	118	Pureed fruit (jar) Fruit juice (liquid)	120 40	89 22
	Pasta	20	71	Pasta + meat +vegetables +potatoes (jar)	100	63
	Vegetables/ Pulses	100	49	Pulses + vegetables + potatoes (jar)	75	38
	Meat	50	41	Meat (5) +vegetables +potatoes (jar)	75	47
	Fish	30	18	Fish +vegetables +potatoes (jar)	75	49
	Dairy based dessert	80	80	Dairy based dessert (with fruit) (jar) Dairy based dessert (with chocolate) (jar)	60 20	59 20
	Oil/butter (4)	5	41
	Total		705	Total		701

Table 4 .

 4 EU basket of "Infant formulae and follow-on formulae" and "Other baby foods" at month 5, as sampled within the CASCADE project -with milk based infant formula follow-on.

			DIET						MARKET BASKET
	Typology	Grams	% Total diet	% "Other baby	foods"	Sampling country	Sampled products	Description	Brand	Market share (%)	(1)	Corrected market	share (%) (2)	Product by	typology (%)	"Other baby	foods" basket (%)	"Infant formulae"	and "Other baby	foods" basket (%)
	Milk
	based
	infant	89	68.3
	formula
	follow on
					Germany	Product 1		BRAND A	27.9	13.95	17.0			11.58
					Germany	Product 2		BRAND A			13.95	17.0			11.58
					Germany	Product 3		BRAND B	26.5	26.5	32.2			22.00
					UK		Product 4		BRAND D	9.3	9.3	11.3			7.72
					France	Product 5		BRAND F	5.9	5.9	7.2			4.90
					Sweden	Product 6		BRAND H	3.6	3.6	4.4			2.99
					Germany	Product 7		BRAND C	3.4	3.4	4.1			2.82
					France	Product 8		BRAND G	3	3	3.6			2.49
					Italy		Product 9		BRAND I_1	2.7	0.9	1.1			0.75
					Italy		Product 10		BRAND I_3			0.9	1.1			0.75
					Italy		Product 11		BRAND I_2			0.9	1.1			0.75
							Total			82.3	82.3	100.0			68.33
	Infant
	cereals
	without
	gluten	20	11.9	37.7
	and
	without
	milk
					France	Product 12	rice vanilla flavour	BRAND F					100.0	37.8	12.00
	Pureed Fruit	80	9.6	30.2
								peaches and
					Germany	Product 13	apple and	BRAND B					50.0	15.1	4.78
								apricots
					Germany	Product 14	fruit peaches, apricots, apple	BRAND B					50.0	15.1	4.78
							Total							100.0	30.2	9.56
	Meat
	+vegetabl
	es	100	10.2	32.1
	+potatoes
	(3)
					Italy		Product 15	beef/chicken	BRAND I_1					16.7	5.3	1.69
					Italy		Product 16	beef/chicken	BRAND I_3					16.7	5.3	1.69
					Italy		Product 17	beef/chicken	BRAND I_2					16.7	5.3	1.69
					Italy		Product 18	mixed vegetables BRAND I_1					50.0	16.0	5.08
							Total							100.0	32.9	10.15
			100	100

Table 5 .

 5 Number of baskets created and of products purchased within the CASCADE project.

	Page 27 of 28	Food Additives and Contaminants
	Types of baskets		Typologies of infant formulae	Number of BASKETS created	Number of PRODUCTS purchased	Country where the products were purchased
	"INFANT FORMULAE AND
	FOLLOW_ON FORMULAE"
	Infant formulae (0-4 months)	Milk based	1
			Soya based	1
			Hypo Allergenic	1
	Follow-on (after 4 th month)	Milk based	1
			Soya based	1
			Hypo Allergenic	1
			TOTAL	6
					18	Germany
					4	UK
	EU				9	France
					1	Portugal
					3	Sweden
					7	Italy
					42	TOTAL
	"OTHER BABY FOODS"		9
					10	Germany
					9	Italy
					1	France
					1	Spain
					1	UK
					22	TOTAL
	"INFANT FORMULAE AND
	FOLLOW_ON FORMULAE"
	Infant formulae (0-4 months)	Milk based	4
			Soya based	4
			Hypo Allergenic	4
	Follow-on (after 4 th month)	Milk based	4
			Soya based	4
			Hypo Allergenic	4
			TOTAL	24
	NATIONAL				6 5	Italy Slovak Republic
					5	Spain
					4	Sweden
					20	TOTAL
	"OTHER BABY FOODS"		4
					4	Italy
					3	Slovak Republic
					3	Spain
					3	Sweden
					13	TOTAL

http://mc.manuscriptcentral.com/tfac Email: fac@tandf.co.uk

http://mc.manuscriptcentral.com/tfac Email: fac@tandf.co.ukFood Additives and Contaminants

Acknowledgements

35

Months

(1) Average body weight in infants of age between month x and month x+1 was estimated by calculating 1) the average of 50th percentile at month x and month x+1 in both females and males, according to WHO 2006 and 2) by calculating the average between the values obtained in females and males. (2) FAO 2004.

(3) For infants of 5 months of age, calculated average energy requirement for 5-6 month (622 kcal/day) was used instead of that for 4-5 month (598 kcal/day). The same was performed for 6th to 9th months of age. (4) SCF 2003.

(5) Energy intake from infant formulae was calculated multiplying the average of the energy content reported on the labels of sampled products (on average, 100 g of rehydrated infant formulae follow-on contain 71 kcal) by the amount of infant formula (ml/day) consumed by infants during the 5h, 6th and 7h month (SCF 2003); the amount of infant formulae follow-on consumed at 8th and 9 th month is assumed to be the same as that consumed at 7 th month (one baby bottle). ( 6)Energy intake from "Other baby foods" were calculated by subtracting the energy intake deriving from "Infant formulae" from the calculated average energy requirements


D Cappelletti
email: david.cappelletti@unipg.it

P Candori

L F Roncaratti

F Pirani

A Molecular Beam Scattering Study of the Weakly Bound Complexes of Water and Hydrogen Sulphide with the Main Components of Air

Keywords: water, molecular interactions, air components water, molecular interactions, air components

Total integral cross section experiments, for collisions of rotationally hot water and hydrogen sulphide projectiles by O 2 and N 2 targets, are reported for the first time. The experimental data allowed the determination of effective potential energy curves which are representative of the intermolecular interactions averaged over all possible relative configurations of these weakly bound complexes. Such information is relevant for the modelling of elementary processes occurring in planetary atmospheres. These experimental determinations have been also used to test the accuracy of intermolecular interactions provided by ab initio calculations, recently available for the water containing complexes.

We further investigated possible experimental effects due to interaction components other than the van der Waals one and some evidences have been found for the complexes of water while these effects appear to be below the experimental sensitivity for the hydrogen sulphide containing complexes.

Introduction

The interaction of water with the major atmospheric species, especially with molecular oxygen and nitrogen, is of great importance in chemistry and biochemistry.

These weakly bound complexes of water may be formed in atmospheric conditions and therefore they are particularly relevant for the understanding of many chemical and physical phenomena of the Earth's atmosphere [1,2]. For example, the absorption of light by complexes of water with the main components of air may play a significant 2 role in several spectral regions, including the infrared [3]. Spectral shifts, enhancements and broadenings of the absorption lines are expected, suggesting that the dynamics of such weakly interacting systems should be included in the energy balance of the Earth's atmosphere [4][5][6]. In addition to the possible atmospheric significances of these hydrated complexes there is a fundamental knowledge to be achieved about the nature and role of the intermolecular interaction in weakly bound systems involving hydrogenated molecules (see for instance [START_REF] Jeffrey | An Introduction to Hydrogen Bonding[END_REF]). Therefore, the study of the homologous complexes of hydrogen sulphide with oxygen and nitrogen may help to clarify similarities and to put in evidence differences respect to those with water [START_REF] Candori | [END_REF].

Experimental information on the present case studies is limited to a microwave spectroscopic characterization of gas phase H 2 O-N 2 [9] and low temperature investigations on solid matrix of H 2 O-N 2 [10,11] and H 2 O-O 2 [12,13].

The latter do not provide significant structural information on the complexes. Some measurements of the second virial coefficients are also available [14,15] but the associated experimental uncertainties are unknown, possibly very large. For H 2 S-O 2 and H 2 S-N 2 experimental studies are hard to find or not published [16]. Direct information coming from gas phase molecular beam scattering experiments, to our knowledge, is not available. Scattering data could be crucial also to test the validity of numerous theoretical calculations available on the intermolecular interactions [10,[17][18][19][20][21][22][23].

The target of the present investigation is the characterization of the intermolecular interaction in such systems, from the analysis of high resolution molecular beam scattering experiments, combined with a phenomenological evaluation of the nature of the intermolecular interaction. As for other cases previously studied [START_REF] Candori | [END_REF][24][25][26][27][28], such an approach is useful to identify the intermolecular potential components that may add to the ubiquitous van der Waals interaction. For example, we recently reported [27,28] the definitive experimental and theoretical assessment of a measurable (half a KJ/mol) charge-transfer (CT) component in the interaction of water with the heavier noble gases. From the experimental side this effect appears clearly also in the effective spherical interaction, as determined by molecular beam scattering experiments since, although being stereo-selective, it is not washed out when averaging over all the possible orientations of the water molecule during each collision. As far as theory, by using an original method of partial water complexes (computed with accurate ab initio methods and basis sets), we mapped the local charge displacement along the whole intermolecular region and were thus able to appraise CT effects free of the inherent ambiguity of charge decomposition models [27,28]. On this line, we have extensively explored by molecular beam experiments similar systems such as water-molecules, ammonia-rare gas and ammonia-molecules, hydrogen sulphide-rare gas and hydrogen sulphidemolecules, methanol-rare gas and methanol-molecules. Their analysis is still in progress and will provide important information on the ample phenomenology concerning the interaction of hydrogenated molecules with other gaseous species. In this paper, we will mostly focus on the experimental characterization of water and hydrogen sulphide molecular complexes with N 2 and O 2 , the main components of air. Herein, rotationally "hot" molecular beams of D 2 O and H 2 S have been generated by a near effusive source and afterwards scattered by N 2 and O 2 targets, introduced into a collision chamber kept at the liquid air temperature. Deuterated water molecules have been used in order to improve the signal to noise ratio during the data acquisition by the mass spectrometer detector. In the case of D 2 O-N 2 system, measurements have been performed also with the scattering chamber at room temperature, in order to probe the effect of the different average rotational period of the N 2 target on the measured cross section. In these experimental conditions the scattering cross sections are essentially sensitive to the spherically averaged intermolecular interaction, which is the main information obtained in this work.

Experimental apparatus

The molecular beam (MB) apparatus used in the present experiments has been described in detail elsewhere [29]. Here only some details relevant for this investigation are given. Briefly, it consists of five differentially pumped vacuum chambers connected by slits for molecular beam collimation. The MB, formed by D 2 O or H 2 S molecules, emerges through a nozzle (1mm in diameter) from a source, which can operate under near effusive or moderately supersonic conditions. The MB is mechanically velocity selected and then crosses a scattering chamber, which can be filled up with the target gas (N 2 or O 2 ) by an automated procedure. The chamber can be maintained at room temperature (T scat =300K) or cooled with liquid air (T scat =90K). The online MB intensity is detected, after the scattering region, by an electron bombardment ionizer followed by a quadrupole mass spectrometer and an electron multiplier.

The molecular beams have been generated by near effusive expansions of D 2 O

or H 2 S vapors through a nozzle heated by a system of wires, which permits to achieve a temperature of about 500 K. Such conditions are important to suppress molecular cluster formation and to produce MBs, which contain molecules with broad rotational distributions. Standard source pressures have been ranged between 2 and 20 Torr (10 2 -10 3 Pa) to cover a wide collision velocity range. The molecular beam velocity analysis and selection have been obtained with the use of a slotted disk velocity selector [26].

The total (elastic + inelastic) integral cross section Q(v) as a function of the selected velocity v of the projectile, is obtained by measuring the beam intensities I (with the target gas in the scattering chamber) and I 0 (without the target gas), and applying the following Lambert-Beer like expression where nl is the product of scattering gas density, n, in the chamber and the length l of the scattering region.

The measure of the absolute values of Q(v) would require an accurate determination of the quantities n and l. Their values are not easy to evaluate exactly since they need an accurate determination of the scattering gas pressure and temperature and also of the effective path, l, along which collisions may happen and which does not exactly coincide with the geometrical length of the scattering cell. The absolute cross section scale has been obtained by an internal calibration of the experimental apparatus, achieved by determining the relative input gas flow of the various target species filling the scattering chamber and by measuring, at selected velocities, the MB attenuation for a system of known cross section. In particular the He-Ar system has been investigated in an extended velocity range [30] for which the absolute cross section values were known [31]. The systematic error introduced by this calibration method is not higher than 3-4 %. to put into evidence the oscillatory structure associated to the "glory" quantum interference. Lines in the figures are calculations of the cross sections to be commented in the following.

As emphasized in the previous section, a heated source has been used to produce rotationally "hot" projectile molecules. In such conditions, it is reasonable to assume that during each collision both projectiles and target molecules have sufficient time to smooth out the effect of the interaction anisotropy. In this way, from the analysis of Q(v) data [28,29,32], it is possible to extract information on an effective radial potential V(r), which depends only on the intermolecular distance r. The obtained V(r) potential is expected to be very close to the average over all relative orientations of the full anisotropic potential energy surface (PES). Moreover, the Q(v) data, measured under the present conditions, are mainly determined by collisional events at large and intermediate impact parameters, where inelastic events play a minor role [33]. Therefore the cross sections here measured in the thermal energy range provide information on the depth of the potential well and on the strength of the long-range attraction [28].

For the analysis of the experimental data we adopted a recently proposed potential model, called Improved Lennard-Jones (ILJ) [34]. According to the ILJ model, the functional form of the interaction potential V(r) is the following where The ε parameter defines the potential well depth; r m fixes the equilibrium distance and β depends on the hardness of the involved chemical species, determining the potential shape in the well region [34]. For the present systems we have used for all the cases β=9, a typical value for non-covalent interactions [START_REF] Candori | [END_REF]26,32,34].

Therefore, during the fitting procedure only the ε and r m parameters have been varied.

Such potential model has been recently applied to describe also anisotropic moleculemolecule interactions [32,35,36] The cross section Q(v), calculated in the center-of-mass frame using the semiclassical JWKB method, are convoluted in the laboratory system, for the comparison with the experimental data, using the procedure illustrated in ref. 29. The final best fit ε and r m parameters are reported in Table 1.

Information on the value of the asymptotic C 6 coefficients has also been extrapolated from the ILJ model. Since the spherically averaged multipolar electrostatic contribution is obviously zero, the isotropic long-range attraction in the present systems is due to dispersion and induction, the latter arising asymptotically from the average interaction between permanent and induced dipoles. Therefore, we assumed C 6 = C disp + C ind and we also expected the long-range induction contribution to be much smaller with respect to the dispersion one. In order to estimate the relative contribution of the two terms we evaluated them from polarizabilities (α) and permanent dipole moments (µ) of the interacting partners. In particular the long-range induction coefficient has been taken C ind ~ αµ 2 while the dispersion C disp has been calculated following the approach presented in Ref. [37]. In this way we estimated a ratio C ind / C disp ≈ 0.10 for H 2 O-X and C ind / C disp ≈ 0.03 for H 2 S-X systems. We also expect any higher order contributions (i.e. those due to permanent quadrupolesinduced dipoles, ect) to be smaller and thus negligible, considering also the present experimental uncertainties. The obtained C disp are compared in Table 2 with data from literature. A general very good agreement is apparent for all the studied systems a part for the H 2 S-N 2 for which the deviation is anyway comparable with the mutual uncertainty between experiment and theory. The best-fit effective spherical potential curves are reported as full lines in Figure 3. The present scattering data has been also used to test the accuracy of the PESs for the H 2 O-O 2 and H 2 O-N 2 systems, as recently obtained through ab initio calculations by Wheatley and coworkers [21,22]. Such anisotropic PESs have been averaged over all the degrees of freedom except for the intermolecular distance between the molecular center of mass, obtaining spherically averaged interactions (points in Figure 3), which have been then easily fitted with the ILJ model potential (dashed lines in Figure 3). These potential energy curves have been employed, in the same fashion as described above, to calculate the scattering integral cross sections for the D 2 O-O 2 and D 2 O-N 2 systems, to be compared with the present experimental determinations. Results of such calculations, shown as dashed lines in Figure 1, agree nicely with the experimental data, as far as the absolute value of the cross sections is concerned. A slight shift at lower energies of the glory position of the ab initio averaged interactions is apparent for both systems, even if it is at the limit of the uncertainty for the D 2 O-N 2 system, whose experimental data have a larger error. Indeed, for the complexes involving N 2 the glory amplitudes appear to be strongly quenched (see Figures 1 and2). This effect is due to the strong interaction anisotropy, arising here from the large electrostatic component associated to the permanent dipole moment of the projectile D 2 O and H 2 S molecules (µ=0.73 and µ=0.38 a.u., respectively [START_REF] Radzig | Reference data on atoms, molecules and ions[END_REF]) and the permanent quadrupole moment of N 2 target (-1.1 a.u. [35,[START_REF] Radzig | Reference data on atoms, molecules and ions[END_REF]), not completely cancelled during the collisions by the rotational averaging effects. This idea is consistent with the observation of a complete quenching of the glory structure in the scattering of D 2 O by "cold" N 2 (see Figure 1 lower panel, T scat =90K). In the case of H 2 S the observed quenching is smaller, because of the smaller dipole moment with respect to H 2 O, and becomes very small when N 2 is substituted by O 2 (see Figure 2 and Figure 1 upper panel), since the permanent quadrupole moment of the oxygen molecule (-0.3 a.u. [START_REF] Radzig | Reference data on atoms, molecules and ions[END_REF]) is much smaller with respect to that of N 2 . This hypothesis has been corroborated by an additional experiment carried out with rotationally "hot" N 2 , (T scat =300K) obtained by keeping the scattering chamber at room temperature. In such conditions the quenching is smaller and the observed glory effect appears to emerge more clearly (see Figure 1 lower panel). An estimation of such effect would require a close-coupling calculation of the cross sections exploiting a full anisotropic PES: this is in line of principle possible and actually we have followed such an approach in the past for a number of systems [33] including molecule-molecule cases [START_REF] Aquilanti | [END_REF]. As a general behavior, the The present analysis has been mainly focused on the position of glory extrema and on the absolute value of Q(v), in order to obtain information on the effective isotropic component of the intermolecular interaction, typically of the van der Waals type, and on further stabilization contributions possibly arising from charge transfer effects. As discussed above, we note again that the strongly anisotropic electrostatic contributions, if not completely washed out by averaging effects due to molecular rotations, will provide essentially a quenching of the glory amplitude and will not affects significantly the quantum interference extema position [29,32,33]. The ε and r m parameters, obtained from the fit of the experiment and reported in Table 1, are compared with the predictions of semi-empirical correlation formulas [37,[40][41][42],

which provide an evaluation of the features of van der Waals interaction, including also the average induction contribution arising from the permanent dipole-induced dipole attraction [41,42]. For systems involving H 2 S, the comparison suggests that semi-empirical predictions and experimental determinations are nearly coincident and this represents a phenomenological probe that the involved interactions are practically of the van der Waals type. On the other hand, for systems involving water, some deviations are appreciable for the complex with O 2 and become more evident for the complex with N 2 . These deviations may be due to charge transfer effects of similar nature as those recently characterized in weakly interacting complexes involving water and rare gases [27,28], which provide an additional stabilization of the molecular complex. Such stabilization becomes effective at intermediate and short intermolecular distances and vanishes at long range where the overlap between the outer molecular orbitals becomes negligible and where the dispersion attraction dominates. This is consistent with the agreement among the long-range attraction C 6 coefficients extrapolated by the ILJ model and the C disp coefficients available from literature (see Table 2).

Conclusions

In this paper we have presented results from molecular beam experiments obtained by scattering rotationally "hot" water and hydrogen sulphide projectiles onto oxygen and nitrogen targets. The experimental data, measured in the thermal collision velocity range, show a "glory" interference pattern superimposed to the usual smooth component of the cross section. Such experimental data allowed the determination of effective potentials which represent, for these weakly bound complexes, the intermolecular interaction averaged over all possible relative configurations of the colliding systems. For water-oxygen and water-nitrogen systems, the present experimental determinations are in a good agreement with calculations exploiting the isotropic component of PESs recently calculated ab initio by Wheatley and coworkers [21,22]. Therefore this is a robust accuracy test of the absolute scale of the average intermolecular interaction of the PESs of these systems, very important for the Earth atmosphere. For the H 2 S-O 2 and H 2 S-N 2 systems, to our knowledge, this is the first experimental determination of intermolecular potential energy curves. A careful analysis of the experimental data, taking into account results from semiempirical calculations and data from similar systems, indicate that for the complexes involving water a charge transfer component may be active in the interaction at intermediate and short range, while for the hydrogen sulphide containing systems these effects are smaller than the experimental sensitivity. Therefore, the present results are also important to cast light on selectivity, strength and role of such component, previously investigated by us on other similar systems [46][47][48][49]. 1. Experimentally determined well depth ε and equilibrium distance r m for the molecule-molecule systems investigated. Maximum estimated uncertainty is 3% for ε, 1% for r m and 2% for the ε r m product. Results from semi-empirical correlations formulas [37,[40][41][42] (maximum estimated uncertainty 15% for ε and 5% for r m ) and ab initio calculations [21,22] [21,22] and dashed lines their ILJ fit curves (parameters in Table 1).

  change in electron density occurring upon the formation of rare gas-

5

 5 Scattering cross sections and information on the phenomenological spherical interactionThe measured integral cross sections Q(v) are plotted in Figures1 and 2for the D 2 O-N 2 , O 2 and for H 2 S-N 2 , O 2 systems respectively. The data are reported as a function of the selected velocity v of the projectile molecules and plotted as Q(v) v2/5

  calculations evidenced a quenching of the glory amplitude with a negligible shift of the glory extrema position. Therefore we think not necessary to perform such calculations for the present systems, also because to the experimental conditions (high rotational temperatures) that would imply a huge number of open coupled channels.

FIGURE 1 Total 2 18 FIGURE 3

 12183 FIGURE 1 Total integral cross sections for the D 2 O-O 2 and D 2 O-N 2 systems as a function of the D 2 O molecular beam velocity. Continuous and dashed lines are calculations as described in the text. In the D 2 O-N 2 case (lower panel) all the Q(v) calculations have been performed at T scat =300 K.

Table 2 .

 2 are also reported for comparison. Experimental C 6 coefficients provided by the ILJ model at the reduced distance, x = r/r m =5, their asymptotic values when x → ∞ and its extrapolated dipole-dipole dispersion component C disp (see text). The maximum uncertainty is about 10%. The values of C disp are compared with values available in the literature. Figure 1. Total integral cross sections for the D 2 O-O 2 and D 2 O-N 2 systems as a function of the D 2 O molecular beam velocity. Continuous and dashed lines are calculations as described in the text. In the D 2 O-N 2 case (lower panel) all the Q(v) calculations have been performed at T scat =300 K.Figure 2. Total integral cross sections for the H 2 S-O 2 and H 2 S-N 2 systems as a function of the D 2 O molecular beam velocity. Continuous and dashed lines are calculations as described in the text.Figure 3. Spherically averaged interaction potential curves for the H 2 O-O 2 and H 2 O-N 2 systems. Open circles are spherically averaged values of the ab initio PESs[21,22] and dashed lines their ILJ fit curves (parameters in Table1).

	System	experimental	semi-empirical	ab initio
		ε (meV)	r m (Å)	ε (meV)	r m (Å)	ε (meV)	r m (Å)
	D 2 O -O 2	13.4	3.72	11.8	3.73	12.0	3.72
	D 2 O -N 2	13.7	3.73	11.7	3.75	11.9	3.81
	H 2 S -O 2	15.0	4.08	14.4	4.05
	H 2 S -N 2	14.4	4.06	14.4	4.07

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Acknowledgements

This research have been supported by the Italian Ministero per la Ricerca Scientifica through PRIN project No. 2008KJX4SN_003. L.F.R. gratefully acknowledge a PhD support by the EU programme Alban.