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Dark chocolate samples were previously classified into four sensory categories. The classification was modelled based on volatile compounds analyzed by direct introduction mass spectrometry of the chocolates&rsquo, headspace. The purpose of the study was to identify the most discriminant odor-active compounds that should characterize the four sensory categories. To address the problem, a gas chromatography-olfactometry (GC-O) study was conducted by 12 assessors using a comparative detection frequency analysis (cDFA) approach on 12 exemplary samples. A nasal impact frequency (NIF) difference threshold combined with a statistical approach (Khi&sup2, test on k proportions) revealed 38 discriminative key odorants able to differentiate the samples and to characterize the sensory categories. A heatmap emphasized the 19 most discriminant key odorants, among which heterocyclic molecules (furanones, pyranones, lactones, one pyrrole, and one pyrazine) played a prominent role with secondary alcohols, acids, and esters. The initial sensory classes were retrieved using the discriminant key volatiles in a correspondence analysis (CA) and a hierarchical cluster analysis (HCA). Among the 38 discriminant key odorants, although previously identified in cocoa products, 21 were formally described for the first time as key aroma compounds of dark chocolate. Moreover, 13 key odorants were described for the first time in a cocoa product.

International audience; Free- and glycosylated-volatile profiles of 14 strawberry varieties, 9 for industrial processing (‘Darselect’, ‘Clery’, ‘Honey’, ‘Honeoye’, ‘Siabel’, ‘FCMO060’, ‘Fraise19’, 2 ‘Senga Sangana’) and 5 for fresh market (‘Gariguette’, ‘Charlotte’, ‘CIR121’, 2 ‘Clery’ (full-field and hydroponic)), were compared. All volatiles were analysed by GCMS. Volatiles from glycosides were first released by direct enzymatic hydrolysis. The extraction method was optimised for furaneol, a key component of strawberry aroma. More than 60 volatile compounds were identified, the most abundant being butyl acetate (average: 17 mg/kg), furaneol (average: 2 mg/kg) and free hexanoic acid (average: 3 mg/kg). Free-volatile profiles showed a split between fresh market strawberries, distinguished by esters and carbonyl molecules like isobutyl acetate or hexanal, and strawberries for processing, distinguished by molecule like 3-penten-2-one and 1-butanol. The three ‘Clery’ profiles were different notably in their hexanal, 4- vinylguaiacol and 3-penten-2-one concentrations. The glycosylated volatile profiles were similar among most strawberry varieties with, as major glycosylated volatiles, hexanoic acid (average: 1.7 mg/kg), benzyl alcohol (average: 0.5 mg/kg), gamma-decalactone (average: 0.5 mg/kg) and coumaran (average: 2.5 mg/kg). The potential for volatile enhancement by deconjugation was different. Potentially fresh market strawberries had a volatile increase of 6% against 50% for strawberries for processing.

Jicaro seeds (Crescentia alata) are widely consumed in Central America, primarily as a popular tasty and nutritious beverage called “horchata”. Seeds are roasted to develop a specific aroma through a process that has never been explored. Volatile compounds, extracted from raw and roasted jicaro seeds (140 °C for 140 s) by SAFE (Solvent Assisted Flavor Evaporation), were analyzed by Gas Chromatography/Mass Spectrometry (GC/MS). Twenty-seven volatile compounds were isolated, among which, ethyl-2-methylbutyrate was designated by olfactometry as providing the characteristic jicaro note (0.16 and 0.47 mg/kg dry basis (d.b.) in raw and roasted seeds, respectively). The release of volatile compounds from the Maillard reaction, such as pyrazines, and the increase of ethyl-2-methylbutyrate after roasting, exhausted the pleasant jicaro aroma. This mild roasting process had a slight impact on polyphenol, fructose and free amino acid contents, in agreement with the Maillard reaction. Confocal microscopy showed the coalescence of lipids in roasted jicaro seeds, which might explain the higher extracted fat content. Programa Regional de Seguridad Alimentaria y Nutricional/[C-15-2012]/PRESANCA II/Italia Consejo Superior Universitario Centroamericano/[C-15-2012]/CSUCA/Guatemala Institut Français Amérique Centrale/[]/IFAC/Costa Rica European Union Latin America Academic Links/[EULA1401013]/EULAlinks/Alemania UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro Nacional de Ciencia y Tecnología de Alimentos (CITA)

International audience; Coffee grown at high elevations fetches a better price than that grown in lowland regions. This study was aimed at determining whether climatic conditions during bean development affected sensory perception of the coffee beverage and combinations of volatile compounds in green coffee. Green coffee samples from 16 plots representative of the broad range of climatic variations in Réunion Island were compared by sensory analysis. Volatiles were extracted by solid phase micro-extraction and the volatile compounds were analysed by GC-MS. The results revealed that, among the climatic factors, the mean air temperature during seed development greatly influenced the sensory profile. Positive quality attributes such as acidity, fruity character and flavour quality were correlated and typical of coffees produced at cool climates. Two volatile compounds (ethanal and acetone) were identified as indicators of these cool temperatures. Among detected volatiles, most of the alcohols, aldehydes, hydrocarbons and ketones appeared to be positively linked to elevated temperatures and high solar radiation, while the sensory profiles displayed major defects (i.e. green, earthy flavour). Two alcohols (butan-1,3-diol and butan-2,3-diol) were closely correlated with a reduction in aromatic quality, acidity and an increase in earthy and green flavours. We assumed that high temperatures induce accumulation of these compounds in green coffee, and would be detected as off-flavours, even after roasting. Climate change, which generally involves a substantial increase in average temperatures in mountainous tropical regions, could be expected to have a negative impact on coffee quality. (Résumé d'auteur)

Cheese flavour results from the activity of many starter and non-starter bacteria that contribute to the conversion of curd components into a number of odorant and sapid compounds. Growing bacteria participate in flavour-related reactions, as well as non‐proliferating or even non‐cultivable bacteria encountered during cheese ripening. Some enzymes released from lysed bacteria can participate as well. Many of the activities are strain-dependent, leading to the need of screening approaches to evaluate the flavouring potential of the strains. This lecture presents the main biochemical pathways for the production of flavour compounds and summarizes the variety of approaches used for screening purpose, with examples ranging from simplified in vitro systems to mini-cheese experiments

Development of volatile compounds contributing to cheese flavour primarily depends on the metabolic activity of bacterial cultures used during manufacture. Gas chromatography coupled to mass spectrometry (GC-MS) preceded by volatiles extraction is widely used for volatile analysis. The volatile profiles of ten strains of Lactobacillus casei/paracasei generated using a cheese model were assessed by GC-MS using two extraction methods, headspace solid-phase microextraction (HS-SPME) with DVB/CAR/PDMS fibre and HeadSpace-Trap (HS-Trap) with Tenax® adsorbent. Chromatographic data was processed using XCMS package of R software. Numbers of total fragments detected were 1788 for HSSPME and 2073 for HS-Trap method. After annotation, 70 and 64 compounds considered as flavour contributors were successfully identified in HS-SPME and HS-Trap profiles respectively, with 40 compounds in common. HS-SPME extracted numerous alcohols, esters and acids, while HS-Trap showed higher selectivity towards short aldehydes and ketones, pyrazine derivatives and specific sulfur-containing compounds. Comparison of common volatiles revealed high correlation in extraction of long-chain ketones and alcohols, but poorcorrelation for aldehydes, sulfur compounds and acids. Principal Component Analysis highlighted similar differences between individual samples using both extraction techniques.Although two extraction techniques identified distinct compounds in the samples, they equally represented differences within the sample set.

Untargeted metabolomics approaches are being developed and appear as a must in the modern food science and microbiology research to investigate food quality and safety. Our objective was to assess the relevance of untargeted metabolomics to explore for the first time Camembert cheese ripening, by using liquid chromatography coupled on-line with high resolution mass spectrometry. Metabolic fingerprints were found to differ significantly depending on the ripening time, pointing out the capacity of this approach to study microbial metabolism within cheese and its influence on the ripening process of Camembert cheese. Nearly a hundred metabolites were identified thanks to in-house and public databases. The results highlighted variations over the ripening process of a large diversity of well-known cheese metabolites such as 13 amino acids and 25 volatile compounds, but also less studied ones such as two vitamins and creatinine. As a consequence, untargeted metabolomics approach appears as a technology-driven opportunity to further deepen the characterization of the overall mechanisms of cheese ripening.

Du fait de problèmes de santé publique, l’industrie agroalimentaire doit réduire la quantité de sel et de matière grasse dans les aliments, et donc dans les charcuteries. Lors de la fabrication des saucissons secs, une diminution combinée des taux de sel et de matière grasse animale peut se traduire par des problèmes de stabilité microbiologique, des défauts d’arôme et de texture dus à des modifications physicochimiques et biochimiques. Dans ce contexte, les objectifs de cette thèse étaient : (1) d’étudier l’impact d’une réduction directe des teneurs en sel et en matière grasse animale sur les évolutions physicochimiques et biochimiques au sein des produits, (2) d’identifier les composés aromatiques responsables de l’arôme du saucisson sec, ainsi que leurs origines, (3) de développer de nouvelles formulations de saucissons secs à teneurs réduites en sodium et en acides gras saturés, et (4) d’étudier les transferts d’eau et sel et de développer une isotherme de sorption spécifique pour le saucisson sec. L’étude de l’effet d’une réduction directe combinée a mis en évidence la difficulté de fabriquer des saucissons secs à teneurs réduites en sel et en matière grasse animale, sans modifier les évolutions physicochimiques et biochimiques. Une identification des composés volatils odorants de saucissons secs de haut de gamme a permis de montrer que l’aromatisation par l’ail et le poivre noir pouvait être un levier technologique permettant d’améliorer la qualité aromatique des saucissons secs allégés en sel et en matière grasse animale. L’impact de l’aromatisation et d’une substitution partielle combinée du sel par le chlorure de potassium et du gras de bardière de porc par l’huile de tournesol oléique sur les propriétés physicochimiques, les réactions biochimiques et les attributs sensoriels de saucissons secs, a été étudié. Cette étude a montré le rôle important de l’aromatisation qui agit en introduisant des molécules aromatiques qui rehaussent l’acceptabilité des produits par les consommateurs, en tant qu’exhausteur de la perception du goût salé et aussi, sur les processus fermentaires qui vont conditionner l’aspect et la texture finale du produit. La substitution partielle combinée est une solution efficace pour conserver au mieux la qualité organoleptique des saucissons, en permettant, d’une part, d’éviter les défauts texturaux et sensoriels liés aux modifications physicochimiques, protéolytiques et lipolytiques générés par une réduction directe combinée, et d’autre part, d’améliorer l’arôme du produit en rehaussant les niveaux d’oxydations lipidique et protéique. L’étude des transferts d’eau et de sel a mis en évidence une migration du sel vers le coeur du saucisson, et a permis de déterminer des valeurs de diffusivité apparente de l’eau en surface de ces produits. Il a été montré qu’une forte réduction en matière grasse réduisait la diffusivité de l’eau à la surface du saucisson. Une isotherme de sorption spécifique permettant de prédire l’aw en fonction des teneurs en eau, en lipides et en sel a été construite en adaptant un modèle de Ross établi pour la gélatine salée et grasse., Because of public health problems, the food industry must lower sodium and animal fat contents in all food products, therefore in cured meat products. During dry-fermented sausage manufacture, a combined reduction both in salt and animal fat contents may induce microbial safety problems and textural and aroma defects due to physical-chemical and biochemical changes. On account of that, this work of thesis aims (1) to investigate the impact of a direct reduction on the salt and animal fat contents on the physical-chemical and biochemical evolutions in the products, (2) to identify the aromatic compounds responsible for the aroma of dry-fermented sausage, and their origins, (3) to develop new nutritionally-improved formulations of dry-fermented sausages with less sodium and saturated fatty acids, and (4) to study the impact of lipid and sodium chloride contents on water transfers in dry-fermented sausages and to build a specific sorption isotherm curve for dry sausages. The study of the effect of a combined direct reduction highlighted the difficulty of manufacturing sodium-reduced fat-reduced dry sausages, without affecting the physicalchemical and biochemical evolutions. Identification of odorous volatile compounds of high quality dry sausages showed that flavouring, especially garlic and black pepper, could be a good solution for improving the aromatic quality of salt-reduced fat-reduced dry-fermented sausages. The impact of flavouring and of a combined salt and animal fat replacement by potassium chloride and oleic sunflower oil, respectively, on physical-chemical properties, biochemical reactions and sensory attributes of dry-fermented sausages was then studied. This specific study showed the crucial role played by flavouring which introduces aromatic molecules that enhance the product acceptability by consumers, which acts as an enhancer of the saltiness perception and which improves the product appearance and texture by boosting the fermentation process. Consequently, the combined partial substitution is an efficient solution to preserve at best the organoleptic quality of the products, allowing, on one hand, avoiding the textural and sensory defects related to physical-chemical, proteolytic and lipolytic modifications induced by a combined direct reduction, and on the other hand, enhancing the product aroma by increasing the levels of lipid and protein oxidations. The study on water and salt transfers highlighted a salt diffusion towards the dry sausage core, and made it possible to determine values of apparent water diffusivity at the sausage surface. We demonstrated that a strong reduction in animal fat content significantly lowered the water diffusivity value at the product surface. A specific sorption isotherm curve based on a modified Ross model was built, allowing dry-fermented sausages water activity to be calculated as a function of water, fat and salt contents.

Session 9 : Processing and Meat Chemical Safety; Nowadays, the control of the contamination of the food chain by toxic xenobiotics became a major safety issue given the strong relationships pointed out between chronic exposure to contaminants and pathologies such as cancers. This issue is particularly critical for animal-derived food products. The current methods operated to ensure this control are expensive, difficult to set up and unsuitable with frequent, regular and large-scale controls required to guarantee effectively the chemical safety of food. A new approach to trace-back these toxic xenobiotics along the food chain may consist in measuring markers of animal exposure to contaminants through omics approach. Among the various classes of metabolism end-products, we focused on volatile compounds which were identified as promising biomarkers to detect pathologies [11] or exposure to contaminants [10]. The present study aims to set up a SPME-MS fingerprinting method to point out the relevance of volatile metabolites in hepatic tissues as markers of chicken exposure to three types of xenobiotics: (i) an organochlorinated insecticide _lindane (γ-HCH), (ii) an environmental micropollutants_a mix of polychlorobiphenyls (PCBs), and (iii) an antibiotic _ ampicillin (Ampisol).

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; International audience; The evolution of aroma compounds from orange juice made from concentrate and stored in glass, standard monolayer polyethylene terephthalate (PET 1), multilayer PET (PET 2) and plasma-treated PET (internal carbon coating) (PET 3) was investigated. Bottles were stored at room temperature (20 degrees C) under artificial light. Volatile compounds in orange juice samples and corresponding packaging materials were analysed at zero time and after 2, 3 and 5 months of storage. After 5 months of storage, from 0.2 to 0.3% of the initial amounts of limonene and beta-myrcene in the orange juice had been absorbed by the plastic packaging materials. Statistical analyses showed that the evolution of aroma compounds was strongly correlated to the duration of storage, but not to the type of packaging material. Indeed, whatever the stored orange juice samples, the same evolutions were observed, with a decrease in aldehydes and ketones, esters, aliphatic alcohols, sesquiterpene and monoterpene alcohols, and an increase in two aliphatic and monoterpene alcohols (i.e. furfural and 4-vinylguaicol). The results suggest that the losses of aroma compounds from the juice could be attributed to the high acidity of the matrix, implying acid-catalysed reactions. Finally, PET packaging materials and their corresponding oxygen permeabilities showed no correlation with the loss of aroma compound.

Microorganisms play an important role in the development of cheese flavour, producing a variety ofaroma compounds for which lactose/citric acid, proteins and fat are precursors. There is a demandfrom cheese producers to diversify the flavour of semi-hard cheeses. A large screening is required toidentify strains of interest among the diversity of cheese-related bacterial species and strains. This stepcannot be bypassed and is time-consuming. Our aim was to develop a methodological approach tofacilitate and expedite the screening of various cheese-related bacteria for their ability to producearoma compounds. Our strategy was to combine: (i) the use of a curd-based broth medium incubatedunder conditions mimicking cheese manufacturing and ripening, ii) a powerful method of extraction ofvolatiles, headspace trap, coupled to gas chromatography-mass spectrometry, and iii) a metabolomicsbasedmethod of data processing using the XCMS package of R software and multivariate analysis.This approach was applied to eleven species: lactic acid bacteria (Leuconostoc lactis, Lactobacillussakei, Lb. paracasei, Lb. fermentum, and Lb. helveticus), surface bacteria (Brachybacterium articum,Brachybacterium tyrofermentans, Brevibacterium aurantiacum, Microbacterium gubbeenense),Propionibacterium freudenreichii and Hafnia alvei. All the strains grew, with maximal populationsranging from 7.4 to 9.2 log CFU/g. In total, 53 volatile compounds were identified, of which 50 variedsignificantly in abundance between bacteria. Principal component analysis of volatile profilesdifferentiated species on their ability to produce ethyl esters (associated with Brachybacterium), sulfurcompounds and branched-chain alcohols (H. alvei), branched-chain acids (H. alvei, P. freudenreichiiand Lb. paracasei), diacetyl and related carbonyl compounds (M. gubbeenense and Lb. paracasei),among others. The present approach was then successfully applied to screen collections of lactic andpropionic acid bacteria. The metabolomics-based method of data processing can be widely applied inthe field of food flavour chemistry.

International audience

La composition phénolique du vin rouge détermine fortement sa qualité: couleur, goût, texture et la plupart des bienfaits pour la santé. Les conditions ambiantes de la vigne modulent l'équilibre hormonal endogène et l'expression de gènes qui contrôlent la voie de synthèse des composés flavonoïdes, en déterminant la composition phénolique finale du raisin. Même s'ils ont été étudiés, les effets des applications des régulateurs de croissance végétale sur l'équilibre hormonal endogène et la qualité du raisin, les effets de ces substances sur la composition et la qualité du vin sont pauvrement documentés. Le traitement des raisins destinés à la vinification avec des régulateurs de croissance végétale est un outil potentiel pour modifier la qualité des raisins et du vin rouge. Ce projet de thèse a pour objectif d’étudier l’impact d'applications de régulateur de croissance végétale sur la composition phénolique des raisins de Vitis vinifera L. cépages Cabernet Sauvignon et Carménère. L’acide abscissique, l’acide indole-3-acétique et l'acide 2-chloroethilphosphonique ont été appliqués à divers stades phénologiques du raisin, doses et conditions environnementales: Les essais ont été menés à Maipo et Cachapoal au Chili et à Bordeaux en France, dans des vignobles commerciaux et expérimentaux ainsi que sur des plantes cultivées en pots. Il a été examiné l'effet de ces traitements sur le contenu interne d'hormones, sur l'expression de gènes structuraux et régulateurs de la synthèse de composés flavonoides et sur la qualité des raisins, en particulier la composition phénolique de sa pellicule. De plus, des vinifications ont été réalisées à partir de raisins traités pour déterminer l'effet des traitements sur la composition chimique et phénolique du vin, ainsi que sur des attributs qualitatifs tels que les arômes et la texture des vins, jugés par un panel d'évaluation sensorielle., Phenolic composition strongly determines red wine quality: color, taste, texture and most health benefits. Vineyard environmental conditions modulate endogenous hormonal balance and gene expression which control the flavonoid biosynthetic pathway leading to final grape phenolic composition. Even when the effects of plant growth regulator applications on grape endogenous hormonal balance and quality have been studied, the effect of these substances on wine composition and quality is poorly documented. The treatment of wine grapes with plant growth regulators is a potential tool in order to modify red wine phenolic composition and quality. This thesis project describes six experiments on plant growth regulator applications on developing grapes of Vitis vinifera L., cvs Cabernet Sauvignon and Carménère. Abscisic acid, Indole-3-acetic acid and 2-chloroethylphosphonic acid were applied in different phenological stages, doses and environmental conditions: Maipo and Cachapoal regions in Chile and Bordeaux region in France, commercial and experimental vineyards and plants in containers. The effect on changes in the internal hormonal content, expression of flavonoid biosynthetic and regulatory genes and grape quality, in particular grape skin phenolic composition were examined. In addition, winemaking was performed in order to assess the effect of treatments on wine chemical and phenolic composition and on wine aroma and texture attributes judged by a sensory panel.

Les réactions d'oxydation impliquant les composés phénoliques semblent induire des modifications non négligeables du profil chimique et sensoriel des vins. Les travaux concernent l’étude des mécanismes réactionnels impliquant certains thiols volatils, contributeurs de l’arôme distinctif et de la complexité des vins des différents cépages avec les composés phénoliques oxydés des vins blancs, principalement les flavan-3-ols. En solution modèle de composition proche du vin, une réactivité différente des thiols volatils selon leur nature chimique vis à vis des formes oxydées des flavan-3-ols a été établie. La synthèse et la caractérisation des adduits par RMN entre les principaux composés phénoliques des moûts et des vins blancs et le 3-sulfanylhexanol, présentant des nuances d’agrumes, a ensuite été réalisée en conditions d’oxydation chimique et enzymatique. La suivi cinétique de la formation des adduits par CLHP-ESI-SM a permis de mettre en évidence une réactivité du thiol spécifique vis à vis d’un substrat polyphénolique, d’établir le rôle catalytique des métaux (Fe2+) et la capacité antioxydante du dioxyde de soufre vis à vis de ces mécanismes réactionnels. La compréhension de mécanismes fondamentaux de la réactivité de la (+)-catéchine et de la (-)-épicatéchine en conditions œnologiques avec les thiols volatils nous a permis de décliner les travaux à l’étude de l’influence de la présence des flavan-3-ols au cours de la vinification et de l’élevage des vins sur ces composants de l’arôme des vins blancs., Oxidation reactions involving phenolics might change wines chemical and sensory profile. The present work concern the study of reactional mechanisms implying certain volatile thiols, responsible of distinctiveness and complexity of various wines, with white wines oxidized phenolic compounds, mainly flavan-3-ols. In a model wine solution, a different volatile thiol reactivity pattern according to their chemical nature with respect to oxidized flavan-3-ols forms was established. The adducts synthesis and characterization by NMR between the principal white musts and wines phenolic compounds and the 3-sulfanylhexanol, presenting citrus fruits nuances, were carried out under chemical and enzymatic oxidation conditions. Their formation monitoring by HPLC-ESI-MS highlighted a specific reactivity of thiol with polyphenolic substrate and established the catalytic role of metals (Fe2+) as well as, the antioxidant effect of sulphur dioxide into these mechanisms. The comprehension of fundamental mechanisms for the reactivity of (+)-catechin and of (-)-epicatechin with volatile thiols in oenological conditions enabled us to elucidate the influence of flavan-3-ols into white wines aroma compounds during wine making and ageing.

Physicochemical properties (partition and diffusion coefficients) involved in the mobility and release of salt and aroma compounds in model cheeses were determined in this study. The values of NaCl water/product partition coefficients highlighted interactions between proteins and NaCl. However, these interactions were not modified by the product composition or structure. On the contrary, model cheese composition and structure influenced NaCl diffusion and both partition and diffusion for aroma compounds. Analysis of in-nose measurements of aroma release during eating, with regard to physicochemical properties, showed that product and aroma properties partly contributed to flavor release. Depending on the model cheese composition, structure and firmness, physicochemical properties, food breakdown, and chewing behavior can lead to different aroma release profiles. Finally, a discussion of all the results with regard to salt and flavor perception of the model cheese showed that both physicochemical and cognitive mechanisms contributed to perception.

National audience

National audience

National audience

National audience

National audience

National audience

La présente invention se rapporte au domaine de la synthèse de composés aromatiques par voie enzymatique ou biologique.L'invention est plus particulièrement relative à un procédé d'obtention d'un précurseur de composés aromatiques, notamment un précurseur de cétone framboise, par bioconversion enzymatique.

National audience

Cheese flavour is the result of a complex mixture of volatile compounds, originating mainly from the enzymatic degradation of curd components by cheese microflora during cheese ripening. Directing cheese flavour development requires knowledge on inter- and intra-species contributions to flavour development, i.e. identification of the volatile (flavour) compounds produced by each strain. The aim of this study was to identify the volatile compounds produced in Swiss cheese by Propionibacterium freudenreichii, one of the species essential for the development of the characteristic flavour of this type of cheese. The volatile profile of compounds obtained from small-scale (1/100) Swiss cheeses, with or without P. freudenreichii, were compared (three strains tested, in association with three thermophilic lactic starters, i.e. twelve cheeses, manufactured in duplicate). Neutral volatile compounds, extracted by dynamic headspace, and free fatty acids were identified using gas chromatography-mass spectrometry. The concentrations of all carboxylic acids and 14 of 58 neutral compounds were significantly higher in the presence of propionibacteria (PAB). The three PAB strains tested produced the same volatile compounds, but observed quantitative differences were strain-dependent. Propionic acid and four propionate esters were detected only in the presence of PAB. Moreover, cheeses with PAB contained two- to three- fold higher levels of free fatty acids derived from lipolysis and five- to fifty- fold higher levels of branched-chain compounds derived from isoleucine catabolism (2-methylbutanal, 2-methylbutanol and 2-methylbutanoic acid) and from leucine catabolism (3-methylbutanoic acid). Lactic starters induced significant variations in the concentrations of some of the compounds produced by PAB, such as methylbutanoic acids and free fatty acids, which varied by 2.0 and 1.4, respectively, as a function of the lactobacilli strains. PAB strains affect the concentration of varied volatile compounds and could therefore have distinct contributions to the formation of Swiss cheese flavour., Les souches de Propionibacterium freudenreichii influencent la concentration de composés volatils variés dans l'emmental. Pour maîtriser la formation de la flaveur du fromage, qui est due à une multitude de composés volatils essentiellement produits par la microflore au cours de l'affinage, il est nécessaire de déterminer comment chaque espèce et souche contribue à la formation de composés d'arôme. L'objectif de cette étude était d'identifier les composés volatils produits dans l'emmental par Propionibacterium freudenreichii, une espèce clé du développement de la flaveur caractéristique de ce fromage. Douze mini-emmentals (échelle 1/100) ont été fabriqués en double, en associant P. freudenreichii (trois souches) et un témoin sans propionibactéries, à trois levains lactiques. Les composés volatils neutres de ces fromages et les acides gras libres ont été analysés par chromatographie en phase gazeuse. Seuls les fromages ensemencés en propionibactéries contenaient de l'acide propionique et quatre esters de propionate. Ces fromages contenaient également 2 à 3 fois plus d'acides gras libres et 5 à 50 fois plus de composés ramifiés volatils issus du catabolisme de l'isoleucine (2-méthylbutanal, 2-méthylbutanol et acide 2-méthylbutanoïque) et de la leucine (acide 3-méthylbutanoïque), avec des différences très significatives selon les souches. Les lactobacilles associés modulaient les concentrations de certains composés produits par P. freudenreichi (acides méthylbutanoïques et acides gras libres). Les souches de P. freudenreichi, en faisant varier la concentration de divers composés volatils, pourraient avoir des contributions distinctes à la formation de la flaveur de l'emmental.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; International audience; Three diploid citrus somatic hybrids (cybrids) were produced by fusions combining nucellar callus-derived protoplasts of Willow Leaf mandarin (Citrus deliciosa Ten.) and Commune clementine (Citrus clementina Hort. ex Tan.) with, respectively, leaf protoplasts of Eureka lemon [Citrus limon (L.) Burm.] and Marumi kumquat [Fortunella japonica (Thunb.) Swing.] and leaf protoplasts of Marumi kumquat. Ploidy and origins of the nuclear, chloroplastic, and mitochondrial genomes were investigated by flow cytometry and nuclear and cytoplasmic simple sequence repeat analyses. Volatile compounds were extracted from the leaves of the three cybrids by a pentane/ether (1:1) mixture, analyzed by GC-MS, and compared to those of their parents. The cybrids were found to be very close to their nucleus-giving parent, suggesting that the main information for volatile compounds biosynthesis is contained in the nucleus. However, nucleo-cytoplasmic interactions occurred: the (mandarin + lemon) cybrid, possessing nucleus and chloroplasts of lemon and mitochondria from mandarin, synthesizes more monoterpene alcohols and esters than its nucleus-giving parent; the (clementine + kumquat) cybrid, possessing nucleus from kumquat and organelles from mandarin, synthesizes more monoterpene and sesquiterpene hydrocarbons and sesquiterpene alcohols than its nucleus-giving parent.

Two mixtures of Propionibacterium freudenreichii commercial strains were tested as adjunct cultures in pasteurized milk Raclette cheese to investigate the ability of propionibacteria (PAB) to enhance flavor development. Cheese flavor was assessed by a trained sensory panel, and levels of free amino acids, free fatty acids, and volatile compounds were determined. The PAB level showed a 1.4 log increase within the ripening period (12 weeks at 11 degrees C). Eye formation, which was not desired, was not observed in PAB cheeses. PAB fermented lactate to acetate and propionate and produced fatty acids by lipolysis, branched chain volatile compounds derived from isoleucine and leucine catabolism and some esters. One of the experimental cheeses received the highest scores for odor and flavor intensity and was characterized by higher frequencies of detection for some minor notes ("propionic"and "whey" odor, "sweet" taste). PAB can therefore be considered as potential adjunct cultures to enhance or modify cheese flavor development.

In spite of its high production (18000 T yearly), very few studies have been devoted to Cantal, a French AOC ("Appellation d'Origine Contrôlée") cheese variety whose making process is close to that of Cheddar. To improve the knowledge of this type of cheese, two ripened Cantal cheeses issued from raw milk and two different industrial processes were biochemically, physicochemically, structurally and microbiologically characterised through the analysis of both cheese sectors and juices extracted by pressure. The results obtained were compared with Cheddar and Emmental cheeses. The main differences between Cheddar and Cantal cheeses of the same age were a higher rate of proteolysis for Cantal cheese shown by both the total nitrogen content and the TCA soluble nitrogen in the respective cheese juices, and higher CaT content as well as an increased molar CaT/PT ratio in the Cantal cheese. Free amino contents in the cheese aqueous phase were similar but individual variations suggested an effect of the secondary ripening microflora provided by the raw milk used. Microbial counts done on different media showed a dominant mesophilic and thermophilic lactic acid bacteria flora, a subdominant flora composed of various ripening bacteria and yeasts and a very low level of some coliforms and of Pseudomonas. An amount of 44 neutral volatile compounds were identified but 3 of them determined by GC-MS (ethanol, 2-butanone and 2-butanol) represented more than 95% of the total peak area. Some variations in these main compounds as well as in minor ones confirmed a difference in the native microflora in the two studied Cantal cheeses. Nevertheless, these data appeared in the range of those reported for Cheddar. The microstructure of fat determined by confocal laser scanning micrography showed that little is present in Cantal cheese as intact fat globules. Most of this component appeared as free fat included in the casein matrix with a high ability to oil off, especially the part which is near the crust. As well as offering a precise characterisation of many compositional aspects of ripened Cantal cheese, this study opens the way for further works on the process kinetics carried out in the making processes and for a better knowledge of the ecosystem metabolism., Microstructure, physico-chimie, flore microbienne et composés aromatiques du fromage de Cantal affiné. En dépit de sa production élevée (18 000 T/an), peu d'études ont été consacrées au Cantal (3e Appellation d'Origine Contrôlée française) dont le procédé de fabrication peut être rapproché de celui du Cheddar. Pour accroître les connaissances sur cette variété de fromage, deux fromages Cantal affinés, obtenus à partir de lait cru, selon deux procédés de fabrication ont été caractérisés analytiquement au plan biochimique, physico-chimique, microbiologique et microstructural, à la fois par l'analyse des fromages et de leurs jus respectifs obtenus par extraction sous pression. Les résultats obtenus ont été comparés aux données existantes sur le Cheddar et l'Emmental. Les principales différences mises en évidence entre Cantal et Cheddar concernent le niveau de protéolyse (teneurs en N × 6,38 et proportion de N soluble dans le TCA accrues par rapport aux jus extraits de Cheddar), une teneur en CaT ainsi qu'un rapport molaire CaT/PT plus élevés dans le Cantal. Si la teneur en acides aminés libres ne différait globalement pas de celle décrite pour le Cheddar, les variations déterminées au niveau individuel suggéraient que l'activité métabolique de la microflore d'affinage (probablement apportée par le lait cru mis en œuvre) était différente entre les deux Cantal étudiés. Les déterminations microbiologiques effectuées à l'aide de différents milieux de culture montraient que la flore était principalement constituée de bactéries lactiques mésophiles et thermophiles. Toutefois, une microflore d'affinage très variée (probablement, propionibacteria, corynebacteria, staphylocoques et microcoques ainsi que des levures), à des niveaux de 104 à 105 ufc*g-1 a pu être identifiée et comparée aux quelques données existantes de la littérature. Une très faible teneur en bactéries indésirables (coliformes et Pseudomonas) a également été dénombrée. Un total de 44 composés volatils neutres ont été caractérisés mais comme pour de nombreuses autres variétés fromagères incluant le Cheddar, trois d'entre eux (éthanol, 2-butanone et 2-butanol) représentent plus de 95 % de l'aire totale des pics déterminés par chromatographie gazeuse couplée à la spectrométrie de masse. La comparaison détaillée des teneurs en composés volatils des deux Cantal étudiés confirmaient la différence d'activité métabolique de la microflore native des laits mis respectivement en fabrication. L'analyse de la microstructure des fromages par microscopie confocale à laser, montrait que l'essentiel de la matière grasse du Cantal se trouvait sous forme non structurée en globules mais bien sous forme d'amas de taille variable ayant une propension aisée à s'extraire de la matrice caséique, et ce particulièrement pour la matière grasse voisine de la croûte du fromage. Les résultats obtenus précisent sur de nombreux aspects les paramètres de composition du Cantal affiné. Ils ouvrent également la voie à de nouveaux travaux tant sur les cinétiques d'obtention mises en œuvre au cours du procédé de fabrication de ces paramètres que sur une meilleure connaissance du métabolisme de l'écosystème d'acidification et d'affinage.

Directing cheese flavour development requires to know the respective contribution of each of the cheese microflora. Volatile (flavour) compounds produced by Propionibacterium freudenreichii, the main secondary flora of Emmental cheese were identified by gas chromatography-mass spectrometry in mini Emmental cheeses, and in pure cultures of propionibacteria grown in cheese aqueous phase (juice). Selected compounds were quantified. Propionibacteria significantly influenced the amount of 57 out of the 69 volatiles identified in juice. Short-chain carboxylic acids (acetic, propionic, butanoic, hexanoic, and isovaleric acids), esters (mainly esters of acetic and propionic acids), and some ketones and alcohols were more abundant in the presence of propionibacteria, whereas most aldehydes were less abundant. Most of these volatiles were branched-chain compounds. In cheese, the fingerprint of propionibacteria on the volatile profile, despite being less pronounced, showed similar trends as in juice. Carboxylic acids and esters are the most probable cheese flavour-active compounds produced by propionibacteria.

Washed-curd cheeses manufactured with either Lactococcus lactis subsp. lactis IL416 or Lactococcus lactis subsp. cremoris AM2 were used to test the role of six Lactobacillus strains from the CNRZ collection as adjunct cultures. Proteolysis and volatile profile determinations were performed on all cheeses after 28 days of ripening; a trained panel assessed sensory characteristics. We observed that overall, the lactococcal starter strains had a major influence on cheese taste and texture. Control cheeses manufactured with the strain IL416 were mild. Lactobacilli adjunct addition to cheeses manufactured with the strain IL416 had a strong effect on their flavour attributes. In contrast, control cheeses manufactured with the strain AM2 had greater flavour intensities and were saltier and more acidic. These cheeses were more affected in their texture profile and overall flavour intensity, and to a lesser extent in their flavour profile by lactobacilli addition. In summary, while the major cheese characteristics are determined by the starter strain used, addition of lactobacilli adjuncts L. plantarum 1572, L. plantarum 1310 and L. casei 1227 can affect flavour and texture of washed-curd cheese products. Des fromages à pâte pressée ont été fabriqués avec soit Lactococcus lactis subsp. lactis IL416, soit Lactococcus lactis subsp. cremoris AM2 pour tester le rôle de six souches de lactobacilles de la collection CNRZ en tant que culture secondaire. La protéolyse et le profil des composés volatils ont été déterminés sur tous les fromages après 28 jours d'affinage et un jury entraîné a établi leur profil sensoriel. Nous observons avant tout une influence majeure de la souche de levain lactocoque sur le goût et la texture des fromages. Les fromages témoins fabriqués avec la souche IL416 sont neutres et l'ajout d'une culture secondaire de lactobacilles a un fort impact sur les attributs de flaveur de ces fromages. Au contraire, les fromages témoins fabriqués avec la souche AM2 possèdent une plus forte intensité de flaveur, ils sont plus salés et plus acides. La texture et l'intensité globale de flaveur et, dans une moindre mesure, le profil de flaveur de ces fromages sont aussi davantage affectés par l'apport d'une culture secondaire de lactobacilles. En résumé, si les caractéristiques principales des fromages sont déterminées par la souche de levain, l'ajout d'une culture secondaire des souches de lactobacilles L. plantarum 1572, L. plantarum 1310 ou L. casei 1227 peut modifier la flaveur et la texture de fromages à pâte pressée. Fil: Hynes, Erica Rut. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Lactología Industrial. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Instituto de Lactología Industrial; Argentina Fil: Bach, Cyrille. Unité de Recherches Laitières et Génétique Appliquée; Francia Fil: Lamberet, Gilles. Unité de Recherches Laitières et Génétique Appliquée; Francia Fil: Ogier, Jean Claude. Unité de Recherches Laitières et Génétique Appliquée; Francia Fil: Son, Olivier. Unité de Recherches Laitières et Génétique Appliquée; Francia Fil: Delacroix Buchet, Agnès. Unité de Recherches Laitières et Génétique Appliquée; Francia

International audience; The relationships between the flavour and composition of half-cooked pressed Abondance cheese (Haute-Savoie, France) were studied under natural cheese production conditions on the basis of different pastures exploited by 3 producers. Cheeses manufactured from milk produced from mountain pastures (M, n = 5, 1500-1850 m) were deemed to be more "fruity" , "animal" , "boiled milk" and "hazelnut" and less pungent and "propionic acid" than cheeses made from milk produced from valley pastures (V, n = 5, 850-1100 m). It was possible to partly attribute these differences in flavour to the presence of protein-based volatile compounds in the cheeses. The V cheeses had a greater variety of flavours than the M cheeses. Cheeses from gramineae-rich pastures had the most intense "cooked cabbage" odours, related to the greater amounts of sulphur compounds in these cheeses. Terpenes, which are more abundant in cheeses produced from dicotyledon-rich pastures, did not contribute directly to cheese aroma. The differences in flavour between the cheeses manufactured by the 3 producers were of the same magnitude as those observed between different pastures used by a same producer. The origin of the volatile compounds in the cheeses - whether of microbial origin or from the feed - was discussed.; Relations entre la flaveur et la composition chimique de fromages d'Abondance fabriqués à partir de laits produits sur différents types de pâturages. Les relations entre la flaveur et la composition des fromages à pâte pressée demi-cuite de type Abondance (Haute-Savoie, France), ont été étudiées dans des conditions naturelles de production du fromage à partir de pâturages différents exploités par 3 producteurs. Les fromages fabriqués à partir de laits produits sur des pâturages de montagne (M, n = 5, 1500-1850 m) ont été jugés plus "fruité " , "animal " , "lait cuit " et "noisette " et moins piquant et " propionique " que les fromages issus de laits produits sur des pâturages de vallée (V, n = 5, 850-1100 m). Ces différences de flaveur ont pu être attribuées en partie à la présence dans les fromages de composés volatils issus du catabolisme des acides aminés. Les fromages V présentaient une plus grande diversité de flaveur que les fromages M. Les fromages issus de pâturages riches en graminées étaient les plus intenses en odeur "chou cuit " , flaveur liée aux quantités plus importantes de composés soufrés dans ces fromages. Les terpènes, plus abondants dans les fromages issus de pâturages riches en dicotylédones, n'ont pas contribué directement à l'arôme des fromages. Les différences de flaveur des fromages entre les 3 producteurs ont été du même ordre de grandeur que celles observées chez un même producteur entre différents pâturages. Les origines microbienne et alimentaire des composés volatils des fromages ont été discutées.

The aim of the work reported here was to underscore major artifacts appearing during the purge-and-trap step of the volatile fraction analysis of water-rich products. For this purpose we humidified the headspace of dry and lowmoisture products to simulate the artifacts produced during the analysis of naturally moist products. This method implemented with and without dry purge of the trapping adsorbent also enabled us to determine the origin of the observed interference. Materials and methods Samples Two food products of animal origin, namely dehydrated beef stock and powdered Parmesan cheese, were selected for their low water content (respectively 2.3 and 25.0 %) and for the diversity of the chemical families present in their volatile fractions. Description of experiments carried out To target the origin of the water-related artifacts, different analyses were carried out with and without humidification of the headspace of the products, and with and without a dry purge step. In all, eight analyses were performed: two products (dehydrated beef stock and Parmesan cheese) in two moisture states (dry and moist) with two drying states for the Tenax trap (with and without dry purge).

Scapanes australis is a major coconut pest in Papua New Guinea. Males exhibit a calling behaviour at night by emitting a liquid secretion at the abdomen tip. Attraction of both sexes to calling males was evidenced in field and olfactometer. Slightly greater EAGs were recorded to male than female volatile collections obtained by conventional adsorbent trapping. EAG activity was lost after concentration and GC failed in disclosing male-specific chemicals. Raw male secretion elicited weak but dose-dependent EAGs. Solid phase micro-extraction (SPME) allowed a decisive breakthrough in isolating and identifying the pheromone. A 84:12:4 (w:w) blend of 1: 2-butanol (67:33 (R)-(-):(S)-(+) ratio), 2: acetoin and 3: 2,3-butanediol (43:17:40 (R,R)-(-): (S,S)-(+):meso ratio) characterised the headspace of male secretion. Chemicals were identified by GC-MS using conventional and chiral capillary columns. Synthetic racemic 1:2:3 blends (8-300 mg/d) plus sugarcane attracted both sexes (2 females:1 male ratio) in field trapping, catching twice to 4 times more beetles than 1 live male in sugarcane. This prompted us to develop a pheromone-based trapping strategy. Comparisons of all possible blends of 1, 2 and 3 evidenced that optimal catches required 1 + 2 while 3 had no effect. The pheromone is thus a blend of 1 and 2, which are the smallest (74

The insertion of a condenser in the dynamic headspace - GC-MS analysis circuit allows part of the water contained in a water-rich sample to be condensed. The impact of such a condenser on the chromatographic profiles of a cheese was stud- ied for temperatures ranging from -12 to 0 °C. The condenser collected the water, but also some of the volatile components of the cheese, irrespective of its operating temperature. Insertion of a condenser improved the overall quality of the chromatogra phic signal, but caused major changes in the chromatographic profile of the cheese.

A dry purge procedure was used to eliminate water during the analysis of the volatile fraction of a water-rich cheese, by dynamic headspace-GC-MS. The impact of the duration of this procedure on chromatographic profile was studied for dura- tions ranging from 0 to 50 minutes. A dry purge duration of 3 minutes sufficed to reduce the water peak area and improve the quality of the chromatographic signal. However, the dry purge procedure induced marked modifications to the chromatographic profile of the cheese throughout the range of component polarities.

International audience

1 table; Quantitative study of volatiles in a model system by a headspace technique

Oenococcus oeni joue un rôle essentiel dans l’élaboration du vin. Adaptée aux environnements acides et riches en alcool, elle est la bactérie lactique naturellement sélectionnée pour mener la fermentation malolactique (FML). Elle est ainsi la principale espèce recherchée et utilisée industriellement comme levain malolactique. Toutefois, il existe une grande diversité phénotypique au sein des souches d’O. oeni et notamment une variabilité des propriétés technologiques que sont la résistance à la lyophilisation, la résistance à l’inoculation dans le vin et la capacité à réaliser rapidement la FML. De nombreux gènes impliqués dans l’adaptation au vin ont déjà été identifiés mais, ne se sont pas toujours révélés efficaces pour la sélection de souches œnologiques. Dans ce contexte, cette étude a consisté à identifier des gènes spécifiques des souches d’intérêt technologique à travers l’analyse des plasmides et génomes. Face aux difficultés rencontrées pour purifier les grands plasmides, seul le plasmide pOENI-1 a été étudié. Ce travail a révélé différentes formes plasmidiques regroupées en une famille nommée « pOENI-1 ». Plusieurs gènes accessoires ont été identifiés et deux d’entre eux ont été détectés chez les souches associées aux fermentations malolactiques spontanées. La comparaison des génomes de souches aux propriétés technologiques diverses a également révélé des séquences génétiques qui leur sont spécifiques. L’ensemble de ces travaux a permis d’identifier plusieurs gènes dont la distribution statistique parmi les souches d’O. oeni a été analysée par la construction de courbes ROC. Ces courbes permettent d’évaluer la qualité des gènes en tant que marqueurs génétiques des souches d’intérêt technologique. Il est donc maintenant possible d’orienter la sélection des nouveaux levains malolactiques par l’utilisation des données génétiques et des outils statistiques décrits dans cette étude., Oenococcus oeni plays an essential role in the production of wine. Adapted to acidic and alcohol rich environments, it is the lactic acid bacterium species that is naturally selected to conduct malolactic fermentation (MLF). It is also the main species that is selected and used industrially as malolactic starter. However, there is a huge phenotypic diversity among strains of O. oeni, which includes a variability of technological properties such as resistance to freeze-drying, resistance to inoculation into the wine and the ability to quickly achieve the MLF. Many genes involved in adaptation to wine have been identified but have not always proven effective in selecting wine strains. In this context, this study aimed to identify genes that are specific strains of technological interest through the analysis of genomes and plasmids. Due to difficulties encountered to purify large plasmids, only the plasmid pOENI-1 was studied. This work has revealed several different but related plasmids that were grouped into a family named "pOENI-1". Several accessory genes have been identified and two of them were detected in O. oeni strains associated with spontaneous MLF. Comparing the genomes of strains showing various technological properties also revealed genetic sequences that are specific of those strains. Altogether, these works have revealed several genes whose statistical distribution among O. oeni strains was analyzed by constructing ROC curves. These curves are used to assess the quality of genes as genetic markers of strains of technological interest. It is now possible to guide the selection of new malolactic starters by the use of genetic data and statistical tools described in this study.

La caractérisation phénotypique de l’espèce Torulaspora delbrueckii en conditions œnologiques, à partir de l’étude d’un grand nombre de souches, a permis de mettre en évidence une grande variabilité au sein de cette espèce. En effet, les souches de T.delbrueckii présentent des différences au niveau des durées de phase de latence et de fermentation, des capacités biotiques mais aussi des productions d’éthanol (maximum 12% vol.). Cette variabilité se retrouve également pour la production d’acidité volatile, de glycérol et de certains arômes. Ce travail confirme les faibles productions d’acidité volatile et de glycérol de cette espèce et met en évidence une réponse au stress osmotique différente de celle de l’espèce Saccharomyces cerevisiae. Au final, l’espèce T. delbrueckii présente une grande « pureté » de fermentation et produit peu de composés indésirables comme le sulfure d’hydrogène, les phénols volatils, l’acetoïne, l’acétaldéhyde et le diacétyle. La réalisation de co-inoculations T. delbrueckii / S. cerevisiae sur moûts liquoreux, permet une réduction systématique de l’acidité volatile des vins, en comparaison à une fermentation pure de l’espèce S. cerevisiae, quelque soit la souche de T. delbrueckii utilisée. De plus, la souche T. delbrueckii OXT1 1//2 a permis de complexifier la composition aromatique d’un moût sec issu du cépage Sauvignon blanc (esters fermentaires +25%, phényl-2-éthanol +51% et thiols volatils +31%). Enfin, la mise au point d’un fermenteur à double compartiment, avec une séparation physique des levures tout en conservant l’homogénéité du milieu de culture, a permis d’aborder l’étude des interactions entre ces 2 espèces. Des inhibitions de type « cell-cell contact » ont ainsi été mises en évidence., The phenotypic characterization of Torulaspora delbrueckii species in enological conditions, using a large number of strains, showed up a wide variability within this species. Indeed, the strains of T. delbrueckii present different fermentative capacities for lag phase and fermentation durations, biotic capacities and ethanol production (up to 12 % vol.). This phenotypic variability is also obtained for the production of volatile acidity, glycerol and certain aroma compounds. This work confirms the low productions of volatile acidity and glycerol of this species and reveals an osmotic stress response distinct from that of Saccharomyces cerevisiae. Finally, the T. delbrueckii species presents a high fermentation purity and produces low levels of undesirable compounds like hydrogen sulfide, volatile phenols, acetoin, acetaldehyde and diacetyl. The realization of co-inoculations T. delbrueckii / S. cerevisiae on high sugar must, allows a systematic reduction of the volatile acidity of wines, in comparison to a pure fermentation of S. cerevisiae. Moreover, co-inoculation with the T. delbrueckii strain OXT1 1 // 2 allowed the increase of aromatic complexity of a Sauvignon blanc dry wine (esters + 25%, 2-phenylethanol +51 % and volatile thiols + 31 %). At last, the development of a fermentor with double compartment allowing a physical separation of yeasts and preserving the homogeneity of culture medium, allowed us to approach the study of yeast interactions. Inhibitions of type “cell-cell contact” have been demonstrated.