Effect of sugar and acid composition, aroma release and assessment conditions on aroma enhancement by taste in model wines

Context: When congruent taste and retronasal aroma are perceived simultaneously, aroma can be enhanced by taste. Different explanations have been proposed: (i) physico-chemical interactions between tastants and aroma compounds, inducing a change of the aroma stimulus before it reaches the receptors, (ii) a contextual bias during sensory tests (dumping), when at least one relevant attribute is not proposed to the panelists to assess a product, (iii) a misunderstanding of the conceptual difference between aroma and taste, or (iv) a perceptual incapability of panelists to distinguish between two congruent percepts. This study was undertaken to better understand aroma enhancement by taste in model wines containing different sugar and acid concentrations but the same volatile composition. Method: We used a twofold approach: model wine retronasal aroma intensity was assessed twice by trained panelists. During the first session, panelists only assessed aroma intensity. During the second session, taste intensity was assessed before aroma intensity, to reduce dumping effects. In-mouth release of volatile compounds was measured by nosespace analysis with the same panelists. Results: Acid concentration influenced aroma compounds release, but it did not impact perceived aroma intensity. Increasing sugar concentration delayed ethyl octanoate (EO) release after swallowing. When taste was not assessed, perceived aroma intensity was not explained by aroma compounds release, but it increased with sugar concentration, probably because of a dumping effect. When taste was assessed, aroma intensity also depended on sugar concentration, but it was significantly correlated to the time of release of EO. Our hypothesis is that when taste declined, late aroma was more easily individualized, and thus assessed with a higher intensity. This entails that panelists focused on aroma to individualize it from taste. We concluded that trained panelists understand the conceptual difference between taste and aroma, but are not completely able to distinguish congruent and simultaneous taste and aroma percepts

Contribution des molécules hydrosolubles non volatiles à la flaveur des fromages (impact sur la saveur et interactions avec des composés odorants)

Résumé françaisDIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

Volatile components of ripe fruits of Morinda citrifolia and their effects on Drosophila

0031-942

Etude par spectroscopies de RMN 23Na , 31P et 1H (effets de la teneur en sel (NaCl) dans des matrices alimentaires)

La réduction de la teneur en sel (NaCl) des aliments est devenue une préoccupation importante en terme de santé publique. Toutefois, les multiples fonctions du sel dans un aliment rendent difficile la réduction de sa teneur. L objectif de ce travail était de démontrer l applicabilité de techniques de RMN pour caractériser la mobilité des ions sodium (différentiation sodium libre/lié), aider à la compréhension du rôle du sel dans l organisation de la matrice alimentaire (en particulier des molécules phosphorées dans des systèmes laitiers) et étudier son impact sur la mobilité de molécules d arômes. Dans un premier temps, l étude par RMN 23Na de gels de iota-carraghénane a permis d une part de valider la quantification du sodium total (expérience Single-Quantum, SQ) et d autre part de démontrer l implication directe des ions Na+ liés dans le processus de gélification de ces polyosides (expérience Double-Quantum Filtered, DQF). La diffusion de molécules d arômes dans ces systèmes a été mesurée par RMN 1H DOSY, mais aucun impact spécifique de la teneur en sel n a pu être mis en évidence. Dans un deuxième temps, des systèmes laitiers et des fromages de type pâte pressée ont été étudiés par RMN 23Na et par RMN du solide 31P avec la technique de rotation à l angle magique (MAS). Nous avons montré la faisabilité des méthodes de RMN 23Na pour la quantification du sodium total et la caractérisation des états de mobilité des ions (présence d ions sodium liés ) dans ces systèmes. Les expériences de RMN MAS 31P (simple impulsion, SPE et polarisation croisée, CP) ont permis d identifier les différentes molécules phosphorées (phosphate inorganique, phosphate de calcium colloïdal, phosphosérines), de déterminer leur répartition, ainsi que de définir leur implication dans le réseau protéiques de systèmes coagulés. A partir de ces résultats, nous avons ainsi pu identifier les paramètres de composition (ou de fabrication) des fromages réels ayant une influence sur la dynamique des ions sodium et sur la répartition des molécules phosphorées, en particulier le phosphore inorganique dans ces fromages. Ce travail démontre que ces techniques innovantes de RMN 23Na et 31P sont parfaitement applicables à des aliments réels et qu elles peuvent contribuer à l orientation du procédé technologique de fabrication de fromages dans l optique d en optimiser les propriétés sensorielles et fonctionnelles.The reduction of salt (NaCl) content in food has become a matter of public health. However, the multiple functions of salt in food make the reduction of its content difficult. The aim of this work was to demonstrate the applicability of NMR innovative techniques in order to characterise the mobility of sodium ions (distinction between free and bound sodium), to bring a better understanding of the role of salt in the organisation of the food matrix (in particular phosphorous molecules in dairy systems) and to study impact of salt on the mobility of aroma compounds. In a first step, the 23Na NMR study of iota-carrageenan gels validated the quantification of total sodium (Single-Quantum, SQ experiment) and also demonstrated the involvement of bound sodium ions in the gelation process of this polysaccharide (Double-Quantum Filtered, DQF experiment). The diffusion of aroma compounds in these systems was measured by 1H DOSY NMR, but no specific impact of salt was evidenced. The second step was dedicated to study dairy systems and semi-hard cheeses by 23Na NMR and solid-state 31P NMR using the magic angle spinning (MAS) technique. We demonstrated the feasibility of 23Na NMR methods for the quantification of total sodium and the characterisation of Na motional state (presence of bound ions) in these systems. 31P MAS NMR (simple pulse excitation, SPE and cross-polarisation, CP) enabled the identification of different phosphorous compounds (inorganic phosphate, colloidal calcium phosphate, phosphoserins), the determination of their proportions and also permitted to determine the involvement of these phosphorous compounds in the protein network of coagulated systems. With these results, we achieved to identify the parameters of composition (or processing) influencing the dynamics of sodium ions in real cheeses. We also determined the distribution of phosphorous compounds, in particular inorganic phosphate, in these cheeses. This work demonstrates that these 23Na and 31P NMR innovative techniques are perfectly applicable to real food and can help to adjust the manufacturing process of cheeses in order to optimise their sensory and functional properties.DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

Etude des transferts de composés d'arôme entre une préparation de fruits et un gel laitier

DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

Dynamiques de croissance de S. thermophilus, L. delbrueckii et L. helveticus dans les fromages à pâte pressée cuite pendant la phase d'acidification sous presse

Trois espèces thermophiles, S. thermophilus, L. delbrueckii et L. helveticus, se développent jusqu à devenir dominantes pendant le premier jour de fabrication des fromages à pâte pressée cuite (PPC) et modifient dès les premières heures de fabrication la composition et le potentiel enzymatique microbien de la matrice fromagère. Ainsi, elles déterminent en grande partie la composition et la structure de la matrice pendant l affinage, et donc les caractéristiques des fromages à la dégustation. Cependant, peu de travaux se sont intéressés à l évolution de l écosystème fromager avant l affinage. Les objectifs de la thèse sont de mieux connaître les dynamiques de croissance in situ de ces trois espèces, et plus particulièrement de mettre en évidence les interactions existant entre ces trois espèces susceptibles de modifier leurs croissances et activités. La stratégie a été de fabriquer des fromages PPC expérimentaux variant uniquement par les ensemencements en espèces thermophiles et d étudier la variabilité des croissances bactériennes, et des caractéristiques reflétant ces activités, dans les fromages. Les résultats montrent qu il existe de nombreuses interactions entre les trois espèces thermophiles pendant le premier jour de fabrication des fromages PPC, dont certaines ont été primordiales pour les croissances bactériennes dans le contexte fromager étudié. La variabilité des croissances a engendré une variabilité des caractéristiques des fromages PPC tout au long de la fabrication. Les perspectives de ce travail sont de proposer des composés impliqués dans les interactions mises en évidence, et d identifier l impact de chaque espèce sur les caractéristiques des fromages.Three thermophilic species, S. thermophilus, L. delbrueckii and L. helveticus, grow at high level over the first day of hard cooked cheese manufacturing, so modifying the cheese matrix composition and the bacterial enzymatic potential in cheese as early as the first hours of manufacturing. Thus, they strongly determined the cheese matrix composition and structure during ripening, and, consequently, the different characteristics of final cheeses. However, few studies have dealt with the evolution of the cheese ecosystem before ripening. The aims of the thesis are to better understand the growth dynamics of the three species in situ during the first day of hard cooked cheese manufacturing, and, particularly, to highlight the interactions between these three species which are likely to modify their growths and activities. The strategy was to make some experimental hard cooked cheeses which only differed by the combination of thermophilic strains inoculated, and to study the variability of the bacterial growths and the characteristics linked with the bacterial activities in these cheeses. Our results show that a lot of bacterial interactions exist between the three thermophilic species over the first day of hard cooked cheese manufacturing; some of these interactions were essential for the bacterial growths in the cheese context of our study. The variability of the bacterial growths generated variability in the characteristics of the hard cooked cheeses over the whole manufacturing. The outlook of this work is to suggest some compounds likely to be involved in the bacterial interactions highlighted, and to identify the impact of each species on the cheese characteristics.DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

Contributo alla conoscenza della natura dei composti volatili responsabili degli odori di frutti di bosco dell'aroma del vino, mediante metodologie di analisi sensoriale e strumentale

DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

The defensive secretion of Eurycotis floridana (Dictyoptera, Blattidae, Polyzosteriinae): Chemical identification and evidence of an alarm function

0965-1748 doi: DOI: 10.1016/S0965-1748(97)00033-7The defensive secretion of the cockroach Eurycotis floridana was believed to contain only (E)-2-hexenal. However, we have shown it consists of 40 components, of which 30 were tentatively identified. (E)-2-Hexenal, (E)-2-hexenol and (E)-2-hexenoic acid represented approximately 98% of the organic phase. The other 2% included 10 aldehydes, 10 alcohols, four acids, two lactones and one ether. Four compounds are novel insect exudates: 3-ethoxyhexanal, 3-hydroxyhexanal, [(E)-1-pentenyl]-4-propyl-1,3-dioxane and 3-[(E)-2-hexenoxyl-hexanal. In addition to its well-known allomonal function, we have demonstrated that the defensive secretion also acts as an alarm pheromone