Gervaise Debucquet

Josiane Cornet

Isabelle Adam

Mireille Cardinal
email: mireille.cardinal@ifremer.fr

Perception of oyster

Keywords: oyster, processing, consumer perception, disgust, social representation

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Introduction

Of the European countries that produce oysters, France is the leader with around 113,000 tons (FranceAgrimer, 2010) and ranks fourth at the world level after China, Japan and Korea.

France has the characteristic to sell nearly all its production on the national market. Oysters (Crassostrea gigas) are a traditional product mainly consumed in their live form, and in spite of the producers' efforts to extend the period of consumption, they still remain a seasonal product for the French market, with a peak of consumption between Christmas and New Year's Day [START_REF] Girard | French consumption of oysters and mussels analysed within the European market[END_REF]. Therefore, in French food culture, oysters belong to the category of rare and luxury foods. A recent survey on household consumption (Panel Kantar Worldpanel) conducted in 2009 for France Agrimer (2010) showed that only 21% of households bought oysters at least once a year even though two thirds of the French population consume the product. This study also confirms a certain stability in consumption, as well as the importance of "cultural", "economic" and "demographic" factors in consumers' behaviour, as already observed by [START_REF] Girard | French consumption of oysters and mussels analysed within the European market[END_REF]. The consumer profile for fresh oysters is essentially a person over the age of 50, in an upper income bracket, living in the West of France and generally in a household of 2 people. On the contrary, non-consumers of oysters, generally among the youngest, consider that this product is too costly and difficult to open, and the specific characteristics of oysters (live, raw and viscous) play a part in developing a certain aversion to this product. This difference in behaviour between young and senior purchasers may lead to a deficit in the recruitment of "new" consumers, and perhaps ultimately leading to critical questions regarding the future of oyster consumption. How can the continuity of oyster consumption be guaranteed down through the generations? This question highlights the importance of promoting the product with young people, but perhaps also of diversifying the range of oyster-based products. This search for new markets could also be an opportunity for processors to extend their range of seafood products.

However, to find the best ways to develop and to avoid possible failure in the market, it is necessary to take into account as early as possible the psychological barriers related to oyster consumption and to analyse the potential for processed oyster-based products through consumer perception. Understanding consumer reactions to new products is especially interesting in the case of oysters as they are known to cause extremely marked reactions.

Many non-consumers are disgusted by oysters because of their appearance and the consumers' unwillingness to consume something alive and viscous. In the literature, "disgust" deals specifically with animal substances versus plant substances because of the moral dimension linked with their ingestion by eaters, as shown by [START_REF] Rozin | A perspective on disgust[END_REF]. In other respects, [START_REF] Kolnai | The standard modes of aversion: Fear, disgust and hatred[END_REF] has identified these two physical characteristics, alive and viscous, as the most common and strongest sources of disgust. French consumers naturally ingest raw, live oysters thanks to French culture which allows them to "appropriate" these particular sensory qualities by classifying them in the category of rare, luxury and healthy food. The feelings of disgust are strongly reduced by the fact that when ingesting oysters a lot of other, generally positive, symbols are ingested at the same time. [START_REF] Fischler | Les Filières Pêche et Aquaculture en France[END_REF] showed that food ingestion is not an ordinary action but one that always has a symbolic dimension. Thus, when eating raw, live oysters, French consumers in general, and those traditionally seen as "oyster eaters" in particular, consider that they are "drinking the sea", conjuring up iodine and all the images of naturality, purity, lightness and freshness associated with this shellfish.

In short, the social representations associated with oysters by consumers identify a healthy and refined food [START_REF] Darmon | L'homme et les microbes[END_REF]. On the contrary, part of the population retains a very strong aversion towards oysters and their physical properties, all the more so if they did not eat raw oysters often and at a young age in their food education.

Processed oysters could thus be a way of removing these fears. In that case, however, it is necessary to analyse expectations and the associated overall perception. Many studies have indeed shown how information or the visual appearance of food influences flavour recognition or overall liking and generates expectations [START_REF] Mojet | Sensory memory and food texture[END_REF][START_REF] Kole | The effects of different types of product information on the consumer product evaluation for fresh cod in real life settings[END_REF][START_REF] Delwiche | The impact of perceptual interactions on perceived flavor[END_REF]; a contrast between expected and actual sensory qualities can induce a strong negative affective response focusing on the unexpected sensory qualities [START_REF] Yeomans | The role of expectancy in sensory and hedonic evaluation: the case of smoked salmon ice-cream[END_REF]. In the case of oyster, the context of the first tasting or first "experience" [START_REF] Faurion | Le goût : un défi scientifique et intellectuel[END_REF] contribute strongly to previous social representations associated with this kind of food and could influence the expected sensory qualities.

In this context, could processing overcome the impact of representations and sensory barriers associated with oyster in non-consumers? Or would deep-seated reasons still prevent consumption for non-consumers? On the other hand, would a traditional consumer of fresh oysters be ready to accept a processed product with the risk of losing certain attributes, such as "natural" and "authenticity"? From a theoretical perspective, this problematic leads to analysis of the phenomenon of anchoring as described by [START_REF] Moscovici | La psychanalyse, son image et son public[END_REF], that is, how the perception of new products and their sensory qualities are determined by previous representations and the social value associated with this food, which is called by [START_REF] Jodelet | Représentations sociales : un domaine en expansion[END_REF], the "already in mind". As this topic has received little attention in the literature on sensory and hedonic evaluation, this article will try to fill the gap.

The general objective of the paper was to analyse and understand the key drivers in oyster or based-oyster products consumption with a twofold research objective: evaluating the impact of processing and social representation on hedonic perception. To achieve these objectives, a complementary approach was applied. A qualitative approach through individual interviews and focus groups was carried out to catch the conscious and unconscious elements in the consumer perception. Then consumer tests were performed on five oyster-based products in two situations of consumption in order to reach a large range of population in term of ages and professional activities (students and active workers in canteens and families with children and teenagers at home). Products were collected from three seafood companies, partners in the project. The range of products making it possible to illustrate the influence of the degree of processing was composed of a frozen, cooked oyster in a half-shell (C) and four sterilized products presented either in cans for soup (S) hot preparations for toast (T) or in glass jar for oyster butter (B) and potted oyster (P). Oyster was entire in the case of C product, mixed in T, B and P products and some pieces of oyster were present in S product. Table 1 gives the main ingredients and characteristics of each product. A preliminary study with a trained panel showed a wide range of sensory characteristics [START_REF] Cardinal | De nouveaux produits pour lever les freins à la consommation d'huîtres et élargir les marchés pour les PME ? Adéquation entre perceptions du consommateur et degré de transformation du produit[END_REF] : in appearance, from smooth, light and homogeneous (P, B) to a more complex product with small pieces and dark colour (T and S); in texture, from a liquid (S) to a paste with different degrees of fat perception (B, P, C); in odour with specific marine notes such as seaweed (T) to vegetable (S) or garlic (B, P) or onion and wine for C; in flavour, from marine notes such as seaweed (T, S) to butter and garlic, especially for B and P. The final objective was to identify if in the range of processed products presented, some of them were mainly adapted to a specific target of consumers.

Study 1: Qualitative study -Individual interviews and focus-groups -

Method

After a first, exploratory stage with in-depth and individual interviews (10 people), four focus-groups of 8 people each (in total 32 people) were made up. During focus-groups, the five products were presented and tasted by the subjects but several projective exercises and open questions were introduced in order to induce spontaneous evocations and collect references to the unconscious, as suggested by [START_REF] Moliner | Formation et stabilisation des représentations sociales[END_REF] as a means of accessing social representations. Each focus-group lasted on average 2 h 30. This qualitative stage aimed (1) at identifying the main factors involved in the consumption or non-consumption of oyster-based products, especially those related to previous social representations associated with oysters and to the recipe itself (the perceived compatibility of the ingredients with oysters, the impact of the degree of oyster processing on acceptability) and (2) to set up hypotheses to be tested in the questionnaire (study 2). Subjects were recruited in the Pays de Loire area and the sample was an equal distribution of age classes, gender, educational level and oyster consumers (C) versus non-consumers (NC). For the recruitment, consumers were informed that the session was a discussion on seafood products with a taste session (no information was delivered on the kind of the products) and therefore they were invited to tell what products they generally consumed and what products they never consumed. They did not know that the session focused on oyster.

In addition, a comparative test on taste perception was implemented during the focus-groups, inspired by the psychophysical experiment by [START_REF] Morrot | The color of odors[END_REF] on odour perception.

These authors investigated the interaction between the vision of colours and odour perception through lexical analysis of experts' wine tasting comments. A white wine artificially coloured red with an odourless dye was described as a red wine in olfactory terms. Analysis showed that the odours of a wine are, for the most part, represented by objects that have the colour of the wine. In our experiment, subjects were offered two samples of the five oyster-based products. The first was a blind test (subjects were told that it was seafood products); for the second, the same five products were offered but they were presented as novel products prepared with oysters. This comparative test was not strictly a sensory test but a projective exercise [START_REF] Donoghue | Projective Techniques in Consumer Research[END_REF] to stimulate verbalization. The aim of this part of the focus-group was in fact to evaluate the influence of previous representations associated with oysters on product perception, especially taste descriptors, and, at the same time, to compare perceptions and assessment of oyster consumers in comparison with non-consumers.

Data analysis

An analysis of themes, sub-themes and lexical universes was carried out with data collected during the focus-groups and individual interviews, and, more particularly, the comments of subjects at both stages of the comparative test.

Results : Impact of oyster representations on hedonic perception of processed products

The lexical analysis of the comments collected during the comparative test showed huge discrepancies both between the first test (blind test) and the second test (the subjects were informed that the products were oyster-based products) and between oyster consumers and non-consumers. The results showed that taste perception is not only dependent on the first sensory experience but also on the pre-existing representations associated with oysters. Taste perception and, more particularly, taste descriptors effectively changed considerably between the first and second tests: we observed that taste initially perceived as "insipid"(10)1 , mainly among the nonoyster consumers (NC) and mostly recruited from young subjects became in the second test "strong"(7), " too strong"(5), "bitter"(3), "acid"(3), that what was called "an indefinable taste"(9) became "strange"(7), "doubtful taste"(4), "a bad aftertaste"(4), and lastly that a texture initially perceived as "soft"(3), "thick"(8) or "heavy"(7) became "jelly-like" (9), and "viscous"(11). All in all, the lexical registers used after being told of the presence of oysters in the recipes showed that simply mentioning oyster revived the main sources of disgust produced by the consumption of raw oyster, that is: viscosity, stickiness and alive; on the other hand, the change in lexical register for taste, perceived first as "good" (9)

or "pleasant"(11) and becoming "not fine or exquisite enough"(5), "not high-class enough"( 6) is mainly observed among the consumers (C). Moreover "Taste of the sea"( 11) became for them "good taste but not strong enough because we don't recognize the taste of oyster enough"(8) or sometimes "not natural enough"( 7), "chemical"(3), and lastly a "delicious and creamy texture"(8) became "like boiled and over-cooked oysters"(6). All in all, these quotations highlight that all the dimensions confer oysters, in the mind of French oyster eaters, with the status of a refined, exceptional and natural dish. Beyond these differences, the products were less appreciated during the second test by both oyster consumers and non-consumers as proved by highly negative comments and bigger amount of leftovers. The subjects were expecting to find oyster-based products "less fatty", "less pasty" and, in some opinions, "the fatty texture suggests that it was fatty oysters or oysters with soft roe". These last quotations confirm that oysters are perceived by most people as a diet and healthy food. In others words, in their mind, fat is not compatible with the representations associated with oyster, that is, hints of the sea, coast, iodine, and mineral salts.

A second part of the focus-groups was dedicated to identifying the boundaries of acceptability as regards recipes and ingredients. As presented in the methodology part, a creativity exercise was implemented during the focus-groups in order to understand what kind of recipes would be accepted or rejected by consumers, according to the nature of the ingredients (meat, fish, fruits, vegetables, dairy products, etc.) and the level of processing of oysters.

Concerning ingredients, the results demonstrated that the association between oysters and meat was rejected by almost everybody. This is an illustration of the impact of cultural habits on acceptability and more particularly of French habits. As oysters are commonly eaten in a raw, live form, the association with meat appears definitively dissonant because of the mixture of "substances", especially "land substances" and lives "sea substances": "They are two different species, from land and sea. So, no! […]. And moreover, meat is a living substance, as are oysters… That is definitely incompatible!". The case of red meat provoked the greatest disgust, because of the blood: "Red meat is not fully dead, it is still a little bit alive. Look at the blood!"2 . The risk arising from this quotation is clearly a symbolic risk and, very logically, white meat (such as pork or chicken) or "reified" meat like ham were better accepted in the recipe with oyster-based products. Lastly, vegetables, as more neutral ingredients, or fish, as ingredients from the same universe, did not raise any problems.

Concerning the level of processing of oysters and therefore the texture of oyster-based products, the participants in the focus-groups stressed the need to clearly identify each ingredient with regard to the issues of mixing "substances". Consumers and non oyster consumers turned down products that were overly processed, of the paste-or blended-type, as they played a part in excessively denaturing the oysters and were perceived as industrial and suspicious products. While the ideal recipe for the oyster consumers was the cooked oyster in a half-shell, because it maintained a symbolic proximity to raw oysters ("Great! They remain in their shell! They look fresh even if they have been frozen!"), on the contrary, nonconsumers looked for intermediary products, neither too mixed and without big pieces of oyster to keep a symbolic distance from the sources of disgust.

Regarding sanitary risk, it is interesting to note that during the focus-groups and after presenting the processed oysters, none of the non-consumers spontaneously tackled this issue.

Surprisingly, the processing of oysters removed all the fears and anxiety about sanitary risk because the "oyster is dead", that is, in the subjects' minds, in biological and symbolical terms. On the contrary, more people among the raw oyster consumers were suspicious of processed oysters because the process was always perceived as a "denaturation" of the oyster, necessarily using additives and preservatives.

In conclusion, the results of the qualitative study revealed huge differences in the mechanisms of perception of oyster-based products between consumers and non-consumers. Our data suggest the importance of previous representations associated with raw oyster on processed oyster perception in terms of taste, recipe acceptability and risk perception.

Study 2: Quantitative study -Consumer test in real consumption situations -

In staff canteens

Method Consumer panel

The French multinational corporation Sodexo, one of the largest food service companies in the world was a partner in the project and offered the opportunity to test products in different staff restaurants. The context of restaurant was particularly interesting because oysters are, in France, almost always consumed in the setting of a social and shared meal. The companies were chosen according to their location and their field of activity in order to reach consumers with different profiles. Three cities that differ from one another in terms of distance from the sea were selected: Nantes, Tours and Lyon. Ifremer, a Marine Research Institute with a consumer population involved in marine questions and the Ecole des Mines , a school of Engineering mainly composed of young consumers, were the two companies chosen in Nantes to test products in their Sodexo restaurants. In Tours, the company selected was Sanofi, from the pharmaceutics sector, and finally Areva, a company working in the nuclear field, in Lyon made it possible to test people in the research department. The four self-service restaurants were different in terms of their mean numbers of daily customers and finally the number of participants in the consumer test was respectively for each restaurant, 155, 177, 87 and 62. The whole panel's characteristics included the four canteens are presented in Table 2.

The amount of oyster eater in this population reached 76%.

Procedure

Tests were performed between December 2009 and April 2010. Products were prepared in each self-service restaurant according to industrial recommendations and were presented at the entry of the restaurant on a plate prepared for each customer. To lighten the test for consumers, the five products were presented on two successive days with a presentation of three products the first day (P, S, T) and two products (B, C), the second day. Products were presented simultaneously on the same plate and consumers tasted the products according to a balanced order in the questionnaire. As the tests lasted for two days, all consumers did not taste necessarily all the products. Each person was informed that the products were oysterbased products and was invited to test them during their lunch. Customers were free to take them or not. After acceptance, the same questionnaire was distributed in each restaurant to collect their opinion. They were invited to give a few negative and/or positive words after tasting each product and to rate their overall liking with a score from 0 to 10: dislike extremely (0), like extremely (10) and to express their perception of naturality, not at all (0), quite natural (10). Personal information such as age, gender, educational level and consumer (C) or non-consumer (NC) of raw oyster was asked for at the end of the session. In the paper, NC refers to non-consumers of raw oyster, the traditional way of eating oysters in France.

Data analysis

Consumer data results were expressed as a mean ± standard deviation (SD). In consumer test, estimation of the effect of each variable (social and demographic characteristics, traditional oyster consumer) on overall liking was performed by analysis of variance on all consumer scores with products and each of these variables as independent factors. The main effects and interaction between factors were tested. The analysis of qualitative data (negative and/or positive words associated to each product after tasting) was only performed on questionnaires from the home tests where description was more detailed and richer than in restaurants.

Results : Overall liking and hedonic perception in staff canteens

The scores for overall liking and "naturality" attributed by consumers to each product are presented in Table 3. The general mean for overall liking scores for all consumers highlights a significant difference between the products. The cooked oyster in a half-shell obtained the highest score (6.9 ± 1.9) followed by soup (6.2 ± 2.4), potted oyster (6.1 ± 2.1), hot toast (5.9 ± 2.2) and finally oyster butter (5.7 ± 2.0), but no significant difference appeared between the last three products. Food habits related to raw oyster consumption had a significant effect (p=0.03) on overall liking as traditional raw oyster consumers gave higher scores to products compared to those of non-consumers. No interaction appears between the variables "usual oyster eater" and products which means a same general trend in overall liking for C and NC.

Analysis of variance performed over all the consumer data of liking with products and gender as independent factors did not show any significant difference between scores attributed by women or men (p=0.43). Educational level and age did not lead to a significant difference either, (p=0.11and p=0.79, respectively).

At home

Method

Consumer panel 145 consumers from 68 households on the Tastenet panel took part in the study. The Tastenet panel was composed of volunteers for consumer tests at home on fish and fish products selected by the French Research Institute Ifremer through the company's staff (friends, family, neighbours). The answers of all family members older than 11 years were taken into account. The majority of theses families lived in an urban area (Nantes). The main characteristics of this at home consumer panel are presented in Table 2.

Procedure

Consumer tests were performed between March and April 2010. Families were provided with the five oyster-based products (here, in their packaging) and a questionnaire for each product and each family member. There was a total freedom to choose the order of consumption of the 5 products as well as the time and the situation of consumption but it was recommended that the products be tested one by one on different days depending on the choice of the family and that the product be prepared according to the directions for use on the packaging. The consumption was organised with the family members previously identified in this home. The same questionnaire as at the self-service restaurants was presented.

Data analysis

The same kind of analysis was applied on overall liking data obtained in staff canteens and at home. Qualitative information obtained from the open questions, especially the negative and/or positive words associated with each product that respondents were asked to provide after tasting, was analysed using textual analysis software called ALCESTE3 version 2010.

This software makes it possible to treat corpora of discourses and to separate statements into classes, using a downwards-hierarchical classification on the basis of co-occurrence of words [START_REF] Reinert | Les "mondes lexicaux" et leur "logique" à travers l'analyse statistique de divers corpus[END_REF]. The classification of the respondents' terms established by ALCESTE was based on the idea that the words used by each respondent were chosen according to his or her particular mental space that constitutes the person's framework of reference [START_REF] Reinert | Quelques problèmes méthodologiques posés par l'analyse de tableaux "Enoncés X Vocabulaire[END_REF].

When data comes from a panel of respondents, it helps to analyse social representations, each class of word used often unconsciously by respondents then resulting from an anchoring process [START_REF] Debucquet | Considérer les normes sociales et culturelles pour une meilleure acceptation des innovations technologiques en alimentation: les leçons du rejet des aliments génétiquement modifiés (OGM)[END_REF], in accordance with the theory of representations developed by the French school of social psychology [START_REF] Moscovici | La psychanalyse, son image et son public[END_REF][START_REF] Jodelet | Représentations sociales : un domaine en expansion[END_REF][START_REF] Moliner | Formation et stabilisation des représentations sociales[END_REF]) which shows how representations are embedded in a social and cultural context. This analysis was performed on questionnaires from the home tests where description was more detailed and richer. Moreover, Chi-square tests were carried out by ALCESTE software to identify significant associations (p<0.05) of each class of words with oyster-based products, sociodemographic profiles, and oyster consumers (C) or non-consumers (NC).

Results : Overall liking and hedonic perception at home

Even if our research is not focused on the consumption context effect, previous studies have shown differences in overall liking between at home test and other situations, it is the reason why results from at home are presented separately. The results of the consumer tests performed at home showed the same order in overall liking as those obtained in staff canteens but the scores attributed were generally lower, except for cooked oyster (Table 4). The highest scores were attributed to cooked oyster and soup with a mean score of 6.9 (± 2.0) and 5.6 (± 2.6) respectively. No significant difference appeared between the other three products. A higher perception of naturality was also associated with the preferred products. In this test, even though oyster consumers, also called "oyster eaters", had better rated soup and potted oyster, the difference in overall liking between "oyster eater" and non-oyster consumer was not significant (p=0.29). As observed in the restaurants, gender and educational level did not affect the overall liking scores. On the other hand, age had a significant effect F 4,4 = 4.5, p=0.001 and the youngest consumers generally attributed lower scores, especially to the soup, hot toast and cooked oyster compared to the upper age class. It is also interesting to note the frequency of refusal for each product (Table 4). Cooked oyster, hot toast and soup were the products with the highest frequencies of non-consumption, respectively, 17.1 %, 14.5% and 13.0% of the whole panel compared to 4.8% and 4.1% respectively for potted oyster and butter. Generally this refusal came from the youngest fraction of the population tested, in this case, the children in the families and also from the non consumers of raw oyster (Table 4).

Once the consumption barrier had been removed and the product tested, consumers provided their hedonic evaluation through a score for overall liking as well as the main descriptors describing the positive and/or negative characteristics for each product. The results from the ALCESTE data processing made up of positive and negative words collected through the open questions in the questionnaire gave some explanations to the perception and overall liking of each product. From the positive evocations provided by the subjects, 2655 specific words were analysed and 74% of the statements classified into 3 classes (Table 5). The largest class (Class 1 -55.0 % of classified statements) focused on the taste of oyster as socially perceived in France: a refined and exquisite taste, combined with the image of a festive, rare and luxury food. The second (Class 2 -37.0%) deals with the texture and appearance of the products in relation to convenience issues (ease of preparation, easy to spread). The last, and smallest (Class 3 -8.0%), expresses the need to compare these unknown products with more familiar fish products, such as fish soup and potted fish. Table 5 gives the significant associations (p<0.05) between these classes and variables as products, socio-demographic profiles and consumer type (C or NC). The butter was associated with class 1, the soup with class 3 and the cooked oyster in a half-shell with class 2. Moreover, older people, men, "raw oyster eaters" (C), and those introduced to oysters early (before the age of ten) were significantly associated with class 1, young people, women, students, and those introduced to oysters rather late (after the age of 20) with class 2, and lastly, people of intermediary age introduced late to oysters with class 3. These results highlight the opposition between younger and older generations regarding food issues (convenience and innovation as regards recipe and way of consumption (aperitif, short meal with friends) versus search for taste and authenticity) and specifically the influence of oyster consumption ("non-oyster eaters" versus "traditional oyster eaters").

From the negative evocations provided by subjects, a larger corpus of 3099 specific words was analysed and 61 % of the statements were classified into 4 classes (Table 6). The largest class (Class 1 -37.0% of the statements classified) contains a lexicon highlighting doubt, fear, and anxiety towards the products as if exposure to oyster-based products would reactivate all the fears associated with raw oyster consumption. Class 2 (29.0 %) focuses on the dissonance resulting from the fatty and pasty characteristic of certain products, perceived as sticky and sickly ("too much cream and butter"). In consumers' minds, oysters are a light, healthy product with small quantities of fat. Class 3 (25.0 %) deals with the taste of the oyster itself, oyster consumers conflicting with non-oyster consumers. The former were deeply concerned about the tastelessness and weak oyster taste of the products whereas the latter often judged the taste of oyster to be "too strong". Lastly, the smallest class (Class 4 -9.0%) focuses on the disgust induced by the presence of big pieces of oyster in the processed products. Concerning the significant associations, the soup and hot toast were associated with class 1, the butter and potted oyster with class 2, the cooked oyster in a half-shell with class 3, and the potted oyster with class 4. These results are consistent with the sensory characteristics previously described by a trained panel (data not shown). Moreover, cooked oyster consumers, born inland and introduced very late to oyster consumption (after the age of 36) were significantly associated with class 1, the "raw oyster eaters" (C) from coastal areas and older people with class 2, young people and students with class 3 and lastly the nonoyster consumers (NC), neither raw nor cooked, with class 4. Once again, these results highlight the impact of previous representations on hedonic evaluation and overall liking, which translated into two opposite lexicons referring to two segments of population, "oyster eaters" and non-consumers.

DISCUSSION

We proposed in this paper to inquire on the key drivers in oyster or based-oyster products consumption and more specifically to focus on the impact of processing and social representation on hedonic perception. Theoretical and methodological issues will be discussed with regards to main results of the different studies.

Theoretical issues

To review the expected results briefly: it was anticipated that processing oysters would decrease disgust among non consumer of raw oysters (NC) and that, at the same time, social representations associated with raw oyster consumption would influence hedonic perception of oyster-based products both among consumers (C) and non consumer (NC). Analysis of data from opened questions (study 2) revealed major differences between consumer (C) and non consumer (NC) as expected. Indeed, significant associations (p<0.05) between lexical classes, products, socio-demographic profiles and consumer type have been found. Consumer (C), older people and those introduced to oyster early were associated with both a class (positive associations) focused on refined and exquisite taste of some products and also a class (negative associations) focused on the tasteless and weak oyster taste of others products.

On the other hand, non consumer (NC), young people and people introduced late to oyster were associated both with a class (positive associations) focused on convenience issues but also with a class (negative associations) focused on anxiety, fear and doubt, oyster-based products consumption reviving unconsciously the main sources of disgust (live, viscous and sticky properties) associated with raw oyster consumption. The comparative test (blind test vs test with information) (Study 1) performed during focus-groups confirmed these results when comparing statements of consumers and of non consumers. Our results match previous research on how the congruence or not of expected and actual flavour has an influence on hedonic evaluation [START_REF] Yeomans | The role of expectancy in sensory and hedonic evaluation: the case of smoked salmon ice-cream[END_REF]. Expanding on what [START_REF] Faurion | Le goût : un défi scientifique et intellectuel[END_REF] wrote, "flavour is not an intrinsic property of a stimulus but the meeting of a food and an eater", our research contributes to better understanding of how previous representations predetermined hedonic evaluation. This issue of expected versus actual flavor seemed to be crucial but covered different meanings according to the kind of consumers (C) versus (NC), in accordance with the theory of social representations and especially the anchoring process [START_REF] Moscovici | La psychanalyse, son image et son public[END_REF]. Finally, our results match and enrich those of [START_REF] Desmet | Sources of positive and negative emotions in food experience[END_REF], who described the impact of positive and negative emotions on food experience, taste perception being namely influence by sensory attributes, experienced consequences, anticipated consequences and personal or cultural meanings; here the impact of social representations associated with oyster consumption, and more broadly speaking, the status of this kind of food in culture have been highlighted.

If we consider now the overall liking of the processed products measured in restaurant and in home (study 2), results showed the same order in the overall liking ranking, with significant differences between cooked oyster (C) and soup (S), the two preferred products and potted oyster (P), hot toast (T) and oyster butter (B), the three less preferred ones. The ranking of products according to the criteria of "naturality perceived" is in the same order and identical in both situations again and is congruent with the opposition observed in previous sensory characterization. This result highlights the importance of the recipe and the nature of ingredient on the perception; the more the recipe is natural the more the image of the product appears congruent with the positive images associated with seafood and sea more widely, as presented before and confirmed with the creativity exercise during focus-groups (study 1).

In accordance with these results, data collected through open questions in the questionnaire (study 2) arose also the fat issue and mainly the incompatibility of fat with oyster. This result gave an other illustration of the importance of social representations associated with oyster, their status in French food culture, their health value, and their source (images of the sea). As mentioned in introduction, oyster is perceived as a luxury and refined food, partly because of its healthy properties, real but also assumed because of the positive imaginary associated with seafood.

Regarding the relationship between consumer profile and overall liking, results of both tests (at home and restaurant test) did not show any effect of gender and educational level. Contrary to raw oyster consumption which can participate, according to the expression of [START_REF] Bourdieu | La distinction[END_REF] in a mechanism of "distinction", oyster-based products seem to have lost their prestigious status because of the industrial process in itself and exactly like for triploid oysters [START_REF] Darmon | L'homme et les microbes[END_REF]. However some contradicting results have been observed concerning the influence of others variables on overall liking and especially the type of consumer (C) vs (NC) and age. In restaurant test, food habits related to raw oyster consumption had a significant effect (p=0.03) on overall liking (scores of consumer (C) higher than scores of non-consumer (NC)) while no significant effect has to be noticed regarding home test. This difference could be attributed to a smaller panel size in home test compared to restaurant test. Conversely, age had a significant effect (F 4.4 =4.5, p=0.001) on overall liking (scores of youngest consumers lower than oldest ones) while no significant effect has been noticed in restaurant test. The higher rate of under 25 years-old consumers, 27.6% at home vs 14.6% in staff restaurants, could explain this difference. Results from focus-group and opened questions in study 2 are consistent with the study of [START_REF] Girard | French consumption of oysters and mussels analysed within the European market[END_REF] namely the relation between the type of consumer and age; oyster eaters being more frequent among people over the age of 50 while non consumer were more often recruited among the youngest. This question arises more widely the issue of first exposure and first tasting and their impact on further sensory experiences as analyzed mainly with children [START_REF] Loewen | Effects of prior exposure to palatable and unpalatable novel foods on children's willingness to taste other novel foods[END_REF]. Individuals' memories of flavour from childhood are typically for foods that are remembered as very palatable or very unpalatable [START_REF] Barker | Building memories for foods[END_REF]. During individual interviews and focusgroups, most of the non-consumers who felt a strong disgust for raw, live oysters were exposed rather late (in average, after 18 years old) to this kind of food unlike the consumers who were used to eating it from a young age, sometimes in the first years of their live even.

Thus, it appears that the earlier the subjects were exposed to raw, live oysters, the less they considered them unpalatable and the more willing they were to taste these new oyster-based products.

Finally, these results bring up the question of the role of both first tasting and social representations, especially for non consumers having to face with a previous disgust for the animal itself. [START_REF] Martins | Human food choices: an examination of the factors underlying acceptance / rejection of novel and familiar animal and non animal foods[END_REF] have shown in the case of food from animal origin the impact of beliefs on hedonic perception, as well as the impact of the assumed negative consequences of eating such foods on acceptation or rejection. The frequency of refusal for each product in home test (study 2) gave interesting information: cooked oyster (C), hot toast (T) and soup (S) are products with the highest frequencies of non-consumption, respectively 17.1 %, 14.5% and 13.0% compared to 4.8% and 4.1% for potted oyster and butter.

Moreover, this refusal came from the youngest fraction of the population tested, children in the families and also from non-consumer (C). These results seem to be relevant: disgust and refusal is more associated with products close to the original form of animal (cooked oyster in half-shell) or containing small pieces of oyster (hot toast and soup). These results highlight here again the impact of processing, as a way to "reify" more or less strongly oyster, on the acceptability of the oyster-based products.

Methodological issues

This complementary approach, including a preliminary sensory analysis with a trained panel, individual interviews and focus groups, and consumer tests made it possible to triangulate the results. Qualitative results from individual and group interviews matched closely those of consumer tests, particularly the open questions included in the questionnaire and scores of the overall liking for the five oyster-based products. On the other hand, the preliminary sensory approach made it possible to bridge some product characteristics, through descriptors, and overall consumer liking, with the latter strongly dependent on the consumption or not of raw oysters. For instance, a strong odour/taste of garlic or seaweed can be valued by nonconsumers and symmetrically rejected by consumers: for the former, it was an original and new odour/taste that did not recall that of oyster, whilst for the latter, it was a "tasteless" product because they did not recognize the "genuine taste of oyster".

One last methodological consideration could be the impact of the tests 'context on the overall liking. Initially, we choose two contexts for the tests, home test and staff canteens test, to reach various profiles of consumers in terms of age, gender and professional activities, active workers, students, teenagers living still in their family, etc. Even though the effect of the context was not a main objective of our research, we can note that the ranking of the overall liking of the 5 products was the same in both cases but the scores attributed at home were generally lower than those given in staff restaurants. Most of the studies where Standardised Situation Tests (SST) and Home Use test have been compared reported higher liking scores in SST than in HUT scores [START_REF] Boutrolle | Comparing central location test and home use test results: Application of a new criterion[END_REF][START_REF] Kozlowska | Hedonic tests in different locations as predictors of apple juice consumption at home in elderly and young subjects[END_REF][START_REF] Murphy | A consumer survey versus panel testing for acceptance evaluation of Marine sardines[END_REF]. However, in a few cases, the reverse has been observed [START_REF] Daillant-Spinnler | Influence of label and location of testing on acceptability of cream cheese varying in fat content[END_REF][START_REF] Hellemann | Role of fat in meal acceptance[END_REF]. For example for high fat version of a cream cheese, consumers were more severe at home than in laboratory. Authors argued "that assessors overestimated the products in the laboratory because during home consumption consumers refer to a broader range of products (i.e. other brands)" and also "the possibility that assessors like to please the experimenter when they rate the products in the laboratory". In our case, the lower scores in home tests could be explained by the status of the oyster-based products themselves and the strong involvement attached to raw oyster consumption in France. As mentioned in the introduction, just as well for consumer and non consumer, raw oyster is a luxury and "highsymbolic value" food strongly associated to family consumption for specifics events. Moreover, as in home tests the families were given the products with their packaging (for 4 products) they became probably more aware of the fact that oyster-based products were processed food, all the more so since the ingredient list was on packaging. Furthermore, it is likely that the family environment developed higher involvement for its members and may therefore have led to more critical analysis [START_REF] Boutrolle | Central location test vs. home use test: Contrasting results depending on product type[END_REF][START_REF] Stroebele | Effect of ambience on food intake and food choice[END_REF][START_REF] De Graaf | A comparison between liking ratings obtained under laboratory and field conditions: The role of choice[END_REF].

Conversely, the social interaction in staff canteens and the limited portion sizes presented to the consumers may explain a generally better evaluation [START_REF] King | The effect of meal situation, social interaction, physical environment and choice on food acceptability[END_REF][START_REF] Boutrolle | Central location test vs. home use test: Contrasting results depending on product type[END_REF].

CONCLUSION

In conclusion, this study showed the impact of social representation, strengthened by the specific initial product characteristics and the positive or negative effects of the first exposure and tasting of raw oyster on perception and its repercussion on expectations or fears related to processed oyster-based products. For instance, contrasted behaviours may appear depending on the initial profile of the consumer, traditional raw oyster consumer or non-consumer. The results allowed us to identify two different market orientations, the first adapted to traditional raw oyster consumers, rather old, with a range of products as close as possible to the natural product, where the oyster taste is clearly recognised; the second aimed at non-consumers of raw oysters, rather young, and proposing products with adapted characteristics, for example an attenuated odour or taste of oyster and a texture with few or even no oyster pieces. For non-raw, live oyster consumers, the more the oyster was processed (such as butter and potted oyster), the less the sources of disgust identified by [START_REF] Rozin | A perspective on disgust[END_REF] and [START_REF] Kolnai | The standard modes of aversion: Fear, disgust and hatred[END_REF] were effective. In their minds, the process played a part in reifying the oyster substance and reducing the aversion. This segmentation also covers expectations of consumers in terms of age distribution, and confirms the opposition between younger and older people. Processing could make possible generational transfer in oyster consumption if these expectations are fulfilled. Nevertheless, the first consumption or the willingness to consume an oyster or an oyster-based product remains a hurdle in the case of non-consumers.

As suggested before, the positive effect of early and frequent exposure, for instance in canteens or university cafeterias, should be exploited in order to have a long-term influence on food choice and the preferences of the younger consumers. However, one of the main limits of our research is the lack of information on real uses and context of consumption. Are these products still adapted to festive and refined consumption according to the French traditional habit or doomed to a more ordinary consumption? The question could be answered through further research. Historians have analysed the importance of the beliefs associated with red meat and blood, especially during the pre-scientific period (Darnon, 1999). A recent research project dedicated to the perception of food germs has shown that blood in red meat is still nowadays perceived as risky because of the survival of the belief in "spontaneous generation" among lay persons [START_REF] Debucquet | La perception des contaminations alimentaires par les consommateurs : analyse des représentations et des pratiques associées à la prévention du risque microbien. 12èmes Journées de Recherche de Marketing de Bourgogne[END_REF].

  Co-occurrents dans les Enoncés Simples d'un Texte (Analysis of co-occurent lexemes in simple wordings of a text) 2 For the two groups (NC and C) constituted of 16 persons (2 focus-groups of 8 persons each), the number in bracket represents the number of citations of each term.

  3

Table 1 .

 1 Oyster-based product characteristics: form, ingredients, presentation and preparation Low educational level: elementary school; middle educational level: secondary school and middle degree professional education; high educational level: secondary school and higher educational level, higher degree of professional education, university or higher Table3. Overall liking in staff restaurant test (mean and standard deviation) according to socio-demographic variables and perception of "naturality" the tested factor and probability associated in the analysis of variance with products and factor used as independent variables 2 Factor levels with different letters are significantly different at p<0.05

		Oyster based	Main ingredients and	Presentation and product preparation
		products	(% of oyster in recipe) when recipe available
	S	Soup	Oyster (15),vegetables, spices	Metallic can; warm in a pan
	P	Potted oyster	Oyster (30), cream, onion, white sauce, butter, garlic	Glass jar, cool before spreading
	B	Oyster butter	Oyster (43), cream, butter, white sauce, onion, garlic	Glass jar, cool before spreading
	T	Hot toast	Oyster (17.5), seaweed, carrot, onion	Metallic can; spread on bread and toast 5
				min in an oven
	C	Frozen oyster	whole oyster with sauce in a half-shell	Cook 10 min in an oven

Table 4 .

 4 Overall liking and perception of "naturality" in the at home test (mean and standard deviation)

			F and p									Products
	Factor	values 1	Factor level	2	P		B		T		S	C
	Consumer	F 4,1 =1.1	C				5.0 (2.3)		4.7 (2.5)		5.0 (2.7)		6.8 (2.6)	6.9 (2.1)
	Type	p=0.29	NC				4.4 (2.2)		5.1 (2.4)		5.1 (2.4)		5.0 (2.5)	6.7 (1.9)
	Age		F 4,4 =4.5	< 25	a		4.8 (2.3)		4.8 (2.5)		5.0 (2.5)		4.3 (2.7)	6.1 (2.0)
			p=0.001	26-35	b c		5.1 (2.4)		4.2 (1.9)		5.2 (2.0)		6.3 (1.8)	7.7 (1.6)
				36-45	a b		4.7 (2.1)		4.8 (2.3)		4.9 (2.5)		5.8 (2.6)	7.0 (1.8)
	Overall			46-55	a b		4.8 (2.7)		4.5 (2.8)		4.5 (2.8)		5.9 (2.7)	6.6 (2.4)
	liking			+55	c		5.1 (1.9)		4.8 (2.6)		6.0 (3.0)		6.5 (2.3)	7.7 (1.5)
	Gender	F 4,1 =0.4	Male				4.7 (2.3)		5.1 (2.5)		5.3 (2.7)		5.8 (2.7)	6.7 (2.1)
			p=0.52	Female		4.9 (2.3)		4.7 (2.4)		4.8 (2.6)		5.5 (2.6)	7.0 (2.0)
	Educational F 4,2 =1.3	Low				5.2 (2.1)		5.1 (2.4)		4.6 (2.4)		4.8 (2.9)	6.4 (1.7)
	level	p=0.27	Medium		4.8 (2.4)		5.0 (2.6)		5.2 (2.8)		6.0 (2.4)	7.1 (2.1)
				High				4.6 (2.4)		4.5 (2.4)		5.1 (2.6)		5.9 (2.5)	7.0 (2.1)
	Products	F 4,643 =16.1 General mean	4.9 (2.3)	a	4.8 (2.5)	a	5.0 (2.6)	a	5.6 (2.6)	b	6.9 (2.0)	c
			p=0.000
	Perception of "naturality"	Products F 4,634 =9.8 p=0.000	General mean	5.1 (2.8)	a	4.7 (2.7)	a	5.1 (2.5)	a	5.9 (2.3)	b	6.6 (2.4)	c
		Refusal to taste	Whole panel %	4.8		4.1		14.5		13.0	17.1
				C			%	4.6		0.9		12.0		11.1	13.9
				NC			%	5.4		13.5		21.6		18.9	27.0

1

F value for the tested factor and probability associated in the analysis of variance with products and factor used as independent variables 2 Factor levels with different letters are significantly different at p<0.05

For the two groups (NC and C) constituted of 16 persons (2 focus-groups of 8 persons each), the number in bracket represents the number of citations of each term.

Historians have analysed the importance of the beliefs associated with red meat and blood, especially during the pre-scientific period(Darnon, 1999). A recent research project dedicated to the perception of food germs has shown that blood in red meat is still nowadays perceived as risky because of the survival of the belief in "spontaneous generation" among lay persons[START_REF] Debucquet | La perception des contaminations alimentaires par les consommateurs : analyse des représentations et des pratiques associées à la prévention du risque microbien. 12èmes Journées de Recherche de Marketing de Bourgogne[END_REF].

Analyse des Lexèmes Co-occurrents dans les Enoncés Simples d'un Texte (Analysis of co-occurent lexemes in simple wordings of a text)

Acknowledgements

This study, carried out with the support of the Pôle Agronomique Ouest and Valorial, was funded by the Brittany and Pays de la Loire regions. The products used in the study were processed by three industrial partners: Cuisine Gourmande, La Belle Iloise and Youinou.

Thanks to Sodexo and especially the staff in the four restaurants in Lyon, Nantes and Tours for their efficient organization in the consumer tests.

Tableau 5. Positive descriptors: lexical classes and significant associations with oyster-based products, socio-demographic profiles, and oyster consumers (C) or non-consumers (NC).

Class description % of classified statements

Lexical universe

Oysterbased product

Socio demographic profiles

Class 1

The 3) Ranking of words in lexical classes and socio demographic characteristics in decreasing order of chi-square values (chi-square value significant at p < 0.05) Tableau 6. Negative descriptors: lexical classes and significant associations with oysterbased products, socio-demographic profiles, and oyster consumers (C) or non consumer (NC).

Class description

% of classified statements

Lexical universe

Oysterbased product

Socio demographic profiles

Class 1

The bizarre and the suspect 37.0 Unpleasant ( 27 Ranking of words in lexical classes and socio demographic characteristics in decreasing order of chi-square values (chi-square value significant at p < 0.05)


Luc Lambs
email: luc.lambs@univ-tlse3.fr

Issam Moussa
email: issam.moussa@ensat.fr

Frederic Brunet
email: brunetfred66@gmail.com

Air Masses Origin and Isotopic Tracers: A Study Case of the Oceanic and Mediterranean Rainfall Southwest of France

Keywords: rainfall, stable isotopes, Mediterranean climate

Aquifers recharge mainly by local rainfall, which depend on the air mass humidity and orographic lifting, causing rain. The stable isotopes of the water molecule, i.e., oxygen-18 and deuterium, are useful tracers to determine the water source origin. Moreover, the calculation of the deuterium excess enables one to differentiate between the air masses from the Atlantic Ocean or the Mediterranean Sea. A transect from one coast to the other one and going through the city of Toulouse have been made to sample the groundwater and determine their isotopic characteristic. A monthly rainfall sampling has also been done over one year, close to the city Toulouse, to see how the d-excess values range over the season. The discussion replaces these results in available isotopic data.

Introduction

France presents a wide range of coasts and is influenced by both the Atlantic Ocean and the Mediterranean Sea. The morphology of this country, which impacts the rainfall pattern, is complex, with the Massif Central in the center, the Alps to the east and the Pyrenees to the south. The main processes controlling the δ 18 O and δD isotopic signatures in precipitations were summarized by Rozanski et al. [START_REF] Rozanski | Isotopic patterns in modern global precipitation[END_REF]; i.e., the rainfall amount, continental and altitude effects and the origin of air masses. For France, some pioneer works have studied the isotopic pattern of rainfall, such as Celle et al., Celle-Jeanton et al., , but still, some areas lack for valuable data, like the Southwest area. It is, therefore, important to constrain the signature of the atmospheric signal in these geographical and geomorphological contexts by means of a rainfall-monitoring network and groundwater measurements.

The Southwest of France presents the characteristics of having two major winds blowing in an opposite direction. For instance, in Toulouse, the northwest wind (280° to 340°), called "Cers", blows during 43% of the year, bringing the moisture from the Atlantic Ocean, and the southeast wind (120° to 180°), called "Autan", blows during 29% of the year, bringing the Mediterranean influences. Therefore the airport runways are oriented N-W/S-E, the planes taking them from one end or the other depending on the wind origin.

The Autan wind is a föhn-type wind deriving from the Marin wind from the Mediterranean and blowing over the Languedoc into the Tarn and the Garonne valleys, affecting the Lauragais (the hilly area between Castelnaudary and Toulouse) and the Toulouse area. Channeled and intensified by the narrowing lowlands between the Pyrenees and the south of the Massif Central, it undergoes sudden acceleration between the Corbières and the Montagne Noire (Venturi effect). Gusts can exceed twice the mean speed, possibly enhanced by lee-wave activity.

To understand the Atlantic Ocean and the Mediterranean Sea on the southwest rainfall of France, the present work summarizes over 75 isotopic measurements of shallow groundwater, used as rainfall natural gauges, located between these two coasts. This study is completed by an 18 months' rainfall survey near Toulouse in view to follow the air masses origin for the rainfall over the season and the influence of the Mediterranean income mainly through the Autan wind.

Experimental Section

Study Area

The Southwest of France stretches between the Atlantic and the Mediterranean coast over 350 km; see Figures 1 and5. For the groundwater, the sampling places were taken in alluvial plains, i.e., along the Garonne and Adour valley at the west and along the Aude valley at the east. The connection between the two basins is Seuil de Naurouze (189 m) located 40 km southeast of Toulouse. Farm wells or piezometers, if available, were used for the shallow groundwater sampling. Typical water depth ranges between 2 and 12 m. The longer groundwater survey has been made near Verdun sur Garonne, 35 km downstream (northwest) of Toulouse, in a farm well (depth 2-4 m), one km away from the Garonne River. It is located in the middle of the Garonne Channel and would be classified as mixed bedrock-alluvial stream [START_REF] Howard | Modeling fluvial erosion on regional to continental scales[END_REF], and the valley contains a classic flight of clay terraces that represent an episodic bedrock valley deepening and punctuated by lateral migration of the deposition of coarse gravels and sands.

Along the west to east transect, the rainfall cumulates at the feet of the Western Pyrenees, with 1156 mm per year in Dax and a little less for Cestas-Pierroton, located north of Bordeaux with 920 mm. After, the rainfall amounts lower along the Garonne Valley with 763 mm in Agen and 660 mm in Toulouse. It increases slowly in the area of Carcasonne 736 mm, due to the proximity of the mountains, before slowing down again in the direction of the Mediterranean Sea: 609 mm in Narbonne, 549 mm in Perpignan and 605 mm in Sète. On the contrary, the evaporation enhance from west to east due to the increasing insulation. 18 O value of the groundwater (in white) and the upstream basin (in red). The resulting isovalue contour for δ 18 O = -5‰, -6‰ and -7‰ are given with a white line, and the two dominant wind directions are given by both arrows.

Rainfall Sampling

Close to our isotopic laboratory in Auzeville, 8 km southeast of Toulouse, a rainfall sampling was installed during June 2011. Its consist of a polypropylene funnel (22 cm diameter) covering a 5 L polypropylene jerrycan, containing 300 mL of paraffin oil to avoid any evaporation process. The rainfall aliquots were sampled monthly, between July 2011 and December 2012. The meteorological data used were obtained from the close INRA station (less than 1 km) and compared with the long-term Toulouse airport station, Blagnac, where the record started in 1809, and located northwest, at 18 km. For each monthly sample, 10 mL were used for δ 18 O and δD determination.

Groundwater Sampling

The shallow groundwater survey started in 1997 at Monbequi near Verdun sur Garonne in farm wells and piezometers to follow the influence of the Garonne River in this meander area [START_REF] Lambs | Correlation of conductivity and stable isotope 18 O for the assessment of water origin in river system[END_REF][START_REF] Lambs | Interactions between groundwater and surface water at river banks and the confluence of rivers[END_REF]. The upper well was chosen as the local ground water reference and samplings were made over 6 years. To get a wider understanding of the alluvial groundwater characteristic, complementary samplings were done along the Garonne Valley between 2004 and 2007, for the Adour Valley between 2005 and 2006 and at the Seuil de Naurouze and Aude Valley in 2010.

Cers wind

Autan wind

Isotopic Measurements

Glass vial of 10 mL with tight caps were used for water sampling. The vials were kept at stable temperature before the measurement of the δ 18 O and δD determination on a continuous flow isotope ratio mass spectrometer. Before 2007, the water samples were send to an iso-analytical laboratory in England (ANCA-GSL and GEO 20-20 IRMS, Europa Scientific, Crewe UK). Each water sample was measured in triplicate for each isotope ratio. The overall mean standard deviation (SD) for the δ 18 O values was around ±0.15‰, and the mean SD for the δ 2 H values was ±1.7‰. From 2010, the measurements were done on our own isotopic platform, Shiva (Isoprim 100 and Geo-multi-flow, Elementar, Hamburg, Germany). Each water sample was measured in duplicate. The mean standard deviation (SD) for the rainfall measurements was around ±0.29‰ for δ 18 O, and the overall mean SD was ±2.5‰ for δ 2 H.

The results are given relative to V-SMOW standards from IAEA. The deuterium excess was calculated using the Global Meteorological Water Line (GMWL), as defined by Craig [START_REF] Craig | Isotopic variation in meteoric waters[END_REF] and completed by Dansgaard [START_REF] Dansgaard | Stable isotopes in precipitation[END_REF]:

d-excess = δD -8 × δ 18 O (1)
A value of d-excess around 10 or below, i.e., similar to the GMWL, was taken as originating from Atlantic moisture and a value around 14 [START_REF] Celle | Signal pluie et traçage par les isotopes stables en Méditerranée occidentale: Exemple de la région avignonnaise[END_REF] as moisture with water recycling as one coming from the close West Mediterranean basin.

Results and Discussion

Rainfall Results

The data were obtained between July 2011 and December 2012. The annual amount of rainfall for 2011 was 538 mm, and for 2012 it was 548 mm in the INRA station and around 20% over the amount values from Blagnac Airport station. These numbers are under the 30 years mean (CLINO period 1961-1990 [START_REF]Climatological Normals (CLINO) for the Period 1961-1990[END_REF]), 671 ± 121 mm per year monthly, as since 2003, the Toulouse area is in a dry period. The obtained isotopic value for δ 18 O ranges from -10.7‰ to -4.0‰, showing the continental influence, with a mean monthly temperature ranging from -2.5 °C (February 2012) for the minimum to +30.4 °C (August 2012) for the maximum. Table 1 reports the obtained isotopes values for the monthly rainfall, with the meteorological data from the nearby INRA station.

In Figure 2, both years are plotted along a whole year and present a similar pattern. The δ 18 O signal presents the more depleted values in winter and the less depleted in summer, following the temperature shift. The negative peak from February 2012 corresponds to a cold period, until -12.5 °C on February 9, with one week of snow. The d-excess displays more erratic variations, perhaps with some evaporative process in summer (July) and a possible Mediterranean influence in October.

Figure 3 gives the representation of δ 18 O versus δ 2 H for both years. For 2011, the regression gives in 2011 a slope of 7.70 and a d-excess of 11.28 with R 2 = 0.979, and in 2012, the slope is equal to 7.70 and a d-excess of 9.85 with a R 2 = 0.909. Both sets are very close with the Global Meteorological Water Line (GMWL) defined by Craig 1961 [9]. The point above the GMWL (δ 18 O = -7.83‰, d-excess = +22.12) corresponds to a possible Autan wind influence with the incoming of Mediterranean rain. The weighted mean (w-mean) of δ 18 O or the d-excess can be calculated by summing the monthly amount of rainfall (rainfall amount month ) relative to the total rainfall for one year and multiplying both monthly isotopic values, according to the following equation:

δ 18 O w-mean = Σ i = 1 to 12 δ 18 O month × Rainfall amount month ÷ Rainfall amount year (2)
The obtained value for the 2012 values is δ 18 O w-mean = -6.32‰ ± 0.25‰ and a d-excess w-mean = 11.76 ± 0.59.

Groundwater Results

Reference Well

The survey of the reference well for the groundwater over six years (see Figure 4) reveals that the δ 18 O values range from -6.18‰ to -7.10‰.The overall mean value of δ 18 O= -6.60‰ ± 0.24‰ (n = 31), whereas the annual mean values range from -6.43‰ to -6.86‰. The seasonal pattern appears very reduced (Δδ 18 O = 0.2 units) for these 31 samples, with a slight depletion in spring. This dampened isotopic amplitude (A GW ) response compared to the rainfall isotopic amplitude (A rainfall ) can be used to calculate the mean residence time (t mr ) according to the exponential model equation of Stichler and Herrmann [START_REF] Stichler | Application of Environmental Isotope Techniques in Water Balance Studies of Small Basins[END_REF]:

Groundwater between Atlantic and Mediterranean Coasts

The numerous alluvial ground water sample along the Garonne, Adour and Aude Valleys shows that there is a gradient from around δ 18 O = -5.0‰ close to the Atlantic coast (-4.6‰ in Dax and -5.4‰ in Bordeaux) and slowly becoming more depleted when coming more inland. At Verdun/Garonne, 50 km downstream of Toulouse, and until Seuil de Naurouze, the highest point (189 m) where the water flux divides itself between the Atlantic and the Mediterranean slope, the δ 18 O reaches -6.6‰. The continental effect continues on the east slope until Raissac, 25 km before the Mediterranean Sea, with a value of δ 18 O around -6.8‰. Along this sea coast, the isotopic values become less depleted, with δ 18 O value close to -5.5‰.

On the contrary, the d-excess starts close to 10 (i.e., the value of GMWL) along the Atlantic coast, before dropping inland, until Toulouse, around 6. From Seuil de Naurouze, the d-excess increases from 8.2, to 9.8 in Raissac, before reaching 12.6 at La Franqui. The Mediterranean Sea is a closed system and displays a higher d-excess value, around 14 [START_REF] Celle | Signal pluie et traçage par les isotopes stables en Méditerranée occidentale: Exemple de la région avignonnaise[END_REF]. The effect of the Mediterranean Sea through the Autan wind affects the d-excess, meaning that the water vapor recycles until Seuil de Naurouze, but the isotopic signal of the of the Continental effect coming from the Atlantic coast stops only a few ten km before reaching the Mediterranean coast, see Figure 5.

Discussion

Most shallow groundwater is of meteoric, i.e., atmospheric origin. Rainwater directly infiltrates the ground or indirectly via the inflow of surface water or from bank storage in streams [START_REF] Geyh | Environmental Isotopes in the Hydrological Cycle[END_REF]. Shallow and locally-derived ground waters are often used to characterize the isotopic content of meteoric waters, due to the conservative nature of the stable isotope composition of water in an aquifer [START_REF] Longinelli | Isotope geochemistry and the water cycle: A short review with special emphasis on Italy[END_REF].

Unconsolidated sediments, like in a river valley, are excellent and most efficient aquifers. Their porosity and permeability are usually high [START_REF] Geyh | Environmental Isotopes in the Hydrological Cycle[END_REF]. We have measured the groundwater velocity in Verdun near our reference well, and the velocity ranges from 2.1 to 3.2 m/day [START_REF] Bats-Landalle | Analyse Géomorphologique de la Plaine d'Inondation de la Garonne[END_REF]. Such alluvial plains present high precipitation response to rainfall, and the residence time of ground water is short. In general, alluvial shallow groundwaters are known to be two to 50 years old [START_REF] Weisman | Dispersion of groundwater age in an alluvial aquifer system[END_REF]. In our case, with the equation of Stichler [START_REF] Stichler | Application of Environmental Isotope Techniques in Water Balance Studies of Small Basins[END_REF], we found a resident time of five years for our groundwater reference well.

On the contrary, deeper groundwater in the Adour-Garonne basin is characterized by more depleted values than the actual mean isotopic rainfall, with values ranging from δ 18 O = -5.6‰ to -10.6‰ [START_REF] Negrel | Isotopes in groundwater: Indicators of climate changes[END_REF]. For instance, in the Southwest of France, we found isotopic values ranging from δ 18 O= -7.2‰ to -7.8‰, (Lambs, unpublished results) for many tens of meters-depth bore wells. Such heterogeneity in the δ 18 O signature for a Paleocene aquifer reflects a variable recharge, either in space and time. The most depleted values correspond to a water recharged with a colder climate than the present one [START_REF] Negrel | Isotopes in groundwater: Indicators of climate changes[END_REF].

From the isotopic results around Toulouse, there is very good agreement between the Verdun groundwater annual average value (δ 18 O mean = -6.60‰ ± 0.25‰) and the rainfall (δ 18 O mean = -6.63‰ ± 1.81‰). For the calculated d-excess, there is a small shift with a mean value of d-excess mean = 6.0 ± 1.7 for the groundwater and d-excess mean = 11.8 ± 4.43 for the rainfall. Notice also that the groundwater taken at the Naurouze pass in 2010 gives similar values (δ 18 O = -6.80‰ ± 0.28‰, d-excess = 8.2 ± 1.9) compared to Verdun groundwater sampled between 1997 and 2003.

On a wider scale, the isotopic fractionation with the altitude is around -0.28 δ 18 O per mil for 100 m of elevation [START_REF] Celle | Signal pluie et traçage par les isotopes stables en Méditerranée occidentale: Exemple de la région avignonnaise[END_REF]. Along our transect, as the mean values of the groundwater around Bordeaux are St Maurice (76 m) -6.77 ± 0.03 n = 3 6.5 +/-1.9

δ 18 O = -5.6‰, at the highest point, Seuil de Naurouze (189 m), the altitude isotopic should at least be -6.2‰, but as the mean Lauragais hill is around 290 m, a correct value would be -6.5‰. Another way is to calculate the continental effect with the ratio of -3.2 δ 18 O per mil for 1000 km inland [START_REF] Millot | Multi-isotopic composition (Li, B, D, O) of rainwaters in France: Origin and spatio-temporal characteristization[END_REF]. From the Atlantic coast at the level of Bordeaux until Seuil de Naurouze, there is 330 km, which should give a fractionation of -1.06, i.e., around -6.66‰, which is in better accordance with the measured values.

If one calculates the continental fractionation until Raissac, 420 km from the Atlantic coast, the new δ 18 O would become -6.94‰, a value more depleted than the observed mean value of -6.83‰.

Rainfall coming from the western Mediterranean basin is known to present less depleted δ 18 O values, but with a d-excess value, around +14 [START_REF] Celle-Jeanton | Isotopic typology of the precipitation in the Western Mediterranean region at three different time scales[END_REF][START_REF] Gat | Effect of Climate Changes on the Precipitation Patterns and Isotopic Composition of Water in a Climatic Transition Zone: Case of the Eastern Mediterranean Sea Area[END_REF]. Such an influence is seen on groundwater δ 18 O values of la Franqui and perhaps also in the higher d-excess of the Raissac area. Even in Toulouse, in October 2012, the abnormal d-excess of the rainfall could come from this Mediterranean inflow. In general, the Mediterranean rainfall seems to be located much closer to the coast, a few tens of kilometers wide. Only the black Autan wind, a particular case of the Autan wind blowing northwest, can bring Mediterranean moisture more inland. However, the amount of this East Mediterranean rainfall remains low compared to the West Atlantic rainfall. The Autan wind is a continental high pressure wind bringing heat and dryness and is influenced by the local orography. Even if different meteorological models try to understand this particular wind [START_REF] Der Emde | High resolution simulation of a flow past the Pyrenees[END_REF][START_REF] Benech | Dynamic characteristics of regional flows around the Pyrenees in view of the Pyrex experiment[END_REF][START_REF] Aouzerats | High resolution modeling of aerosol dispersion regimes during the Capitoul field experiment: From regional to local scale interactions[END_REF], it is often not announced in the weather forecast.

Table 2 reports the rainfall isotopic data available in the Global Network of Isotopes in Precipitation (GNIP) database from IAEA [START_REF]Global Network of Isotopes in Precipitation[END_REF]. For Toulouse, the data is from the present work (year 2012), as there is no other data on the GNIP database. However, it is possible to get the calculated interpolated data from the area of Toulouse [START_REF] Bowen | The Online Isotopes in Precipitation Calculator[END_REF], which is δ 18 O = -6.2‰ ± 0.3‰. This value is a little less than our mean value (δ 18 O mean = -6.6‰ ± 1.8‰), but equal to our weighted mean: δ 18 O w-mean = -6.32‰ ± 0.25‰. For the slope between the δ 18 O and δD values, only Toulouse presents a value close to the GMWL (respectively, 7.70 and 8.00). All the other places on both coasts display a lower slope, due to a smaller δ 18 O. It is not necessarily a problem of coastal influence or the evaporation process. In fact, the GMWL as a global line is made of many small local lines with slopes that are often smaller than eight. There is a good correspondence between the calculated δ 18 O weighted mean of Bordeaux (in fact, Cestas-Pierroton) and our mean groundwater of this area (respectively, -5.69‰ and -5.59‰) and also the calculated δ 18 O weighted mean of Dax and our mean groundwater of this area (respectively, -4.59‰ and -4.86‰). With these δ 18 O weighted means, the continental effect from west to east between Bordeaux and Toulouse is around one unit and the latitude effect between Bordeaux and Dax, also one unit of δ 18 O. One can also notice the equivalent of δ 18 O weight mean values of Dax and Montpellier (respectively, -4.59‰ and -4.17‰), nearly on the same latitude, but on a different sea coast. The calculated weighted d-excess mean is always high, i.e., between nine and 12, and only in Avignon, it drops at around eight.

The study of the West Mediterranean influence is complex, as it is a transition zone between the cool North Atlantic air masses and the warm and wet air flowing from the Mediterranean basin. The isotopic signal of the air masses from these different origins crossing the Mediterranean may be modified by water vapor produced in the Mediterranean [START_REF] Celle-Jeanton | Isotopic typology of the precipitation in the Western Mediterranean region at three different time scales[END_REF]. The d-excess value of the water vapor of the Mediterranean region results from the intensive evaporation near the coast, under conditions of a large humidity deficit [START_REF] Gat | Isotope composition of air moisture over the Mediterranean Sea: An index of the air-sea interaction pattern[END_REF]. All these particular features from the Mediterranean water vapor reveal the importance of the study to understand the local climate by monitoring numerous and long-term rainfall and groundwater sampling.

Conclusions

The present study is the first one to provided isotopic rainfall data for the Toulouse area in connection with numerous alluvial groundwater sampling over the Southwest of France. These results reveal that this area is influenced by both the Atlantic and the Mediterranean climate, but also, a continental effect is perceptible through the wide isotopic range. The Mediterranean influence is mainly brought by the Autan wind, but the isotopic composition of the groundwater is only influenced closer to a few tens of kilometers from the Mediterranean shore. Only some d-excess higher value can reveal it. More sampling of rainfall at the month scale still needs to be done for this area to better understand this specific climate. Furthermore, sampling of individual special rain events, like after the Autan wind, is now also performed for trying to refine these possible Mediterranean moisture inflows.

Figure 1 .

 1 Figure 1. The Southwest of France with the localization of the sample sites with the typical δ 18 O value of the groundwater (in white) and the upstream basin (in red). The resulting isovalue contour for δ 18 O = -5‰, -6‰ and -7‰ are given with a white line, and the two dominant wind directions are given by both arrows.

Figure 2 .Figure 3 .

 23 Figure 2. Monthly variation of (a) δ 18 O and (b) d-excess with error bars for the rainfall in 2011 (dotted line, no symbol) and 2012 (plain line, cross symbol) near Toulouse.

  a residence time of about five years.

Figure 4 .

 4 Figure 4. Variation of the δ 18 O values of the reference groundwater well near Verdun sur Garonne (between 1997 and 2003) over the season. The solid line represents the polynomial regression line.

Figure 5 .

 5 Figure 5. Continental gradient from the west Atlantic coast to east Mediterranean coast: mean isotopic values (δ 18 O, d-excess) for the different alluvial ground water stations along the Garonne, Adour and Aude Valleys. The altitude of the station is given between brackets.

Table 1 .

 1 Isotopic results, calculated d-excess and meteorological conditions for the rainfall samples near Toulouse.

	Month	δ 18 O (‰)	δ 2 H (‰)	d-excess	Rainfall Min. T Max. T (mm) (°C) (°C)
	July 2011	-4.48	-28.15	7.69	86.5	14.9	25.7
	August 2011	-4.00	-19.02	12.98	21.5	16.3	29.0
	September 2011	-5.18	-27.18	14.24	73.5	14.8	27.2
	October 2011	-6.59	-36.73	15.98	24.5	9.6	21.7
	November 2011	-10.71 -72.56	13.12	31.0	9.6	15.9
	December 2011	-5.62	-30.45	14.51	53.0	5.0	12.1
	January 2012	-6.55	-40.87	11.53	39.0	3.8	10.3
	February 2012	-10.22 -71.81	9.95	4.0	-2.5	6.0
	March 2012	-5.80	-32.00	14.40	22.0	4.1	17.5
	April 2012	-6.71	-44.17	9.51	69.0	7.6	16.2
	May 2012	-4.80	-24.84	13.56	75.5	11.6	22.2
	June 2012	-4.67	-27.23	10.10	53.5	15.0	26.5
	July 2012	-4.53	-29.61	6.63	58.0	14.7	27.5
	August 2012	-6.28	-39.35	10.89	48.5	17.5	30.4
	September 2012	-5.25	-28.96	13.05	26.0	13.9	24.7
	October 2012	-7.83	-40.53	22.12	53.0	11	20.5
	November 2012	-8.89	-55.92	15.20	49.5	6.8	14
	December 2012	-8.09	-59.80	4.93	50.5	4.6	11.6

Table 2 .

 2 Comparison of the isotopic features of the GNIP stations and our Toulouse station.

	City	Slope d-excess R 2	δ 18 O w mean (‰)	d-excess w	δ 18 O range Rainfall (‰) (mm)	Year
	Dax	6.09	0.32 0.948 -4.59 ± 0.95 9.71 ± 1.24 -6.84--2.25	1156 1999-2005
	Bordeaux 6.90	3.90 0.925 -5.69 ± 0.65 10.18 ± 0.32 -7.16--4.33	920	2007-2009
	Toulouse 7.70	9.86 0.909 -6.32 ± 0.25 11.76 ± 0.59 -10.71--4.00	548	2012
	Montpellier 6.49	3.07 0.825 -4.17 ± 0.14 9.07 ± 2.07 -6.65--1.79	595	1997-1998
	Avignon 7.19	2.31 0.984 -5.49 ± 1.20 7.39 ± 2.95 -7.83--2.23	619	1997-2009

Acknowledgments

We would like to thank Florent Barbecot (University of Paris Sud) and Stephan Terzer (IAEA, Vienna) for their advice for the rainfall isotope sampling, Romain Walker (Ecolab) for Figure 1 and Daniel Dalger (Ecolab) for help with the isotopic analysis. For the meteorological data, we are grateful to Pierre Perrin (INRA Auzeville) and Meteofrance (Blagnac airport), and for the two anonymous reviewers for their valuables comments.