Interactions between 10 aroma compounds from different chemical classes and 5 mixtures of milk proteins have been studied using static or dynamic headspace gas chromatography and solid-phase microextraction (SPME). Static headspace analysis allows the quantification of the release of only the most abundant compounds. Dynamic headspace analysis does not allow the discrimination of flavor release from the different protein mixtures, probably due to a displacement of headspace equilibrium. By SPME analysis and quantification by GC-MS (SIM mode) all of the volatiles were quantified. This method was optimized to better discriminate aroma release from the different milk protein mixtures and then from oil/water emulsions made with these proteins. The highest difference between the release in different proteins was observed for ethyl hexanoate, which has a great affinity for beta-lactoglobulin. Ethyl hexanoate is thus less released from models and emulsions containing this protein.

-We studied three complex food emulsions which differed only by the weight ratio of casein-to-whey proteins (80:20, 60:40, 0:100). We considered the stability of the fat droplets against aggregation/coalescence, the amount of adsorbed proteins, and the protein composition of the interface. Our results indicated that coalescence was inhibited whatever the protein composition. However, aggregation between fat droplets was observed in the casein-free emulsion (0:100), where the amount of adsorbed proteins at the fat globule surface was the lowest. Quantitative SDS-PAGE experiments showed that preferential adsorption of caseins over globular proteins occurs only in the emulsion based on the intermediate (60:40) casein-to-whey protein ratio. Furthermore, the proportion of adsorbed proteins which were found in polymeric forms seemed to increase with decreasing casein-to-whey protein ratio. The fat globule stability, total fat protein load and proportion of adsorbed protein in the polymeric forms were discussed in terms of adsorption properties of milk proteins at the oil-water interface, in relation to the casein-to-whey protein ratio.Milk protein / emulsion / stability / protein adsorption / disulfide bond Résumé -Composition de la couche protéique adsorbée à la surface des globules gras dans des émulsions alimentaires complexes contenant différents rapports caséine/protéines sériques. Nous avons étudié trois émulsions alimentaires complexes qui ne diffèrent entre elles que par le rapport massique caséine/protéines sériques (80:20 ; 60:40 et 0:100). Cette étude a été réalisée en considérant la stabilité des gouttelettes lipidiques vis-à-vis de l'agrégation/coalescence, la quantité de protéines adsorbées par unité de surface de globule gras et la composition de l'interface. Nos résultats ont montré l'absence de coalescence dans les trois émulsions, et la présence d'agrégats n'a été observée que dans l'émulsion (0:100) ne contenant pas de caséine. Dans ce dernier cas, la quantité de protéines adsorbées à la surface des globules gras est la plus faible. Une étude quantitative par électro-phorèse sur gel de polyacrylamide a indiqué une adsorption préférentielle des caséines par rapport aux protéines sériques dans le cas de l'émulsion préparée à base du ratio intermédiaire (60:40) de caséine/protéines sériques. De plus, la proportion de polymères adsorbés à la surface de globules gras semble augmenter lorsque le rapport massique caséine/protéiques sériques diminue. La stabilité des émulsions, la charge protéique des globules gras et la proportion de polymères adsorbés sont discutées en fonction du rapport caséine/protéines sériques.Protéine laitière / émulsion / stabilité / adsorption des protéines / pont disulfure

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A specific experimental procedure suitable for the quantification of four esters recently identified in a wine of Vitis vinifera cv. Pinot Noir, ethyl dihydrocinnamate (A), ethyl cinnamate (B), methyl anthranilate (C), and ethyl anthranilate (D), was developed and applied to 33 Burgundy wines (calculated on three replicates). The method, involving a stable isotope dilution assay, allows the determination of concentrations from 0.05 μg L-1, with a repeatability better than 10%. The mean, maximum, and minimum amounts found for the four esters were as follows (in μg L-1):  (A) 1.6, 3.2, 0.8; (B) 0.8, 1.6, 0.5; (C) 0.2, 0.6, 0.06; (D) 2.4, 4.8, 0.6. Differences between wines, according to their concentrations and the nature of the esters, were visualized by principal component analysis. An analysis of variance indicated that ethyl anthranilate was the most important for wine differentiation. Keywords: Pinot noir; wine; aroma; stable isotope SIM-MS