Recherches sur le potentiel aromatique des raisins de Vitis vinifera L. cv. Sauvignon blanc

Le développement d'une méthode de dosage par dilution d'isotopes stables, de trois S-conjugués à la cystéine, précurseurs de thiols volatils responsables de l'arôme du Sauvignon, permet d'apprécier le potentiel aromatique des raisins de ce cépage. Cette méthode est un dosage indirect des précurseurs cystéinylés, basée sur l'analyse des thiols volatils correspondants, libérés par percolation du moût sur une colonne de tryptophanase immobilisée. Au cours de la maturation, l'évolution des teneurs en précurseurs cystéinylés du raisin varie en fonction du S-conjugué à la cystéine considéré et des conditions climatiques du millésime L'alimentation en eau joue un rôle essentiel sur le potentiel aromatique des raisins. La distribution des précurseurs cystéinylés dans la baie diffère selon le précurseur considéré : 80 % des S-4-(4-méthylpentan-2-one)-L-cystéine et S-4-(4-méthylpentan-2-ol)-L-cystéine se situent dans le jus et plus de 50 % du S-3-(hexan-1-ol)-L-cystéine (P-3MH) sont dans la pellicule. Par conséquent, la macération pelliculaire améliore le potentiel aromatique du moût mais a une incidence essentiellement sur le P-3MH. Les thiols volatils sont libérés à partir de leur précurseur sous l'action de la levure. La révélation du potentiel aromatique du sauvignon dépend donc entièrement de la fermentation alcoolique. Le taux de transformation des précurseurs cystéinylés en arôme est très faible. De plus, le taux de dégradation des S-conjugués à la cystéine varie en fonction de la souche de levure inoculée, mais il est davantage influencé par la composition du moût. L'identification du S-3-(hexan-1-ol) glutathion dans le moût de sauvignon fournit des indications sur la voie de biosynthèse du P-3MH dans la vigne, car les S-conjugués au glutathion sont généralement impliqués dans les voies de détoxification chez les organismes vivants.BORDEAUX2-BU Santé (330632101) / SudocBORDEAUX1-BU Sciences-Talence (335222101) / SudocVILLENAVE D'ORNON-Bib. ISVV (335502201) / SudocSudocFranceF

Individual differences in AMY1 gene copy number, salivary α-amylase levels, and the perception of oral starch.

The digestion of dietary starch in humans is initiated by salivary α-amylase, an endo-enzyme that hydrolyzes starch into maltose, maltotriose and larger oligosaccharides. Salivary amylase accounts for 40 to 50% of protein in human saliva and rapidly alters the physical properties of starch. Importantly, the quantity and enzymatic activity of salivary amylase show significant individual variation. However, linking variation in salivary amylase levels with the oral perception of starch has proven difficult. Furthermore, the relationship between copy number variations (CNVs) in the AMY1 gene, which influence salivary amylase levels, and starch viscosity perception has not been explored.Here we demonstrate that saliva containing high levels of amylase has sufficient activity to rapidly hydrolyze a viscous starch solution in vitro. Furthermore, we show with time-intensity ratings, which track the digestion of starch during oral manipulation, that individuals with high amylase levels report faster and more significant decreases in perceived starch viscosity than people with low salivary amylase levels. Finally, we demonstrate that AMY1 CNVs predict an individual's amount and activity of salivary amylase and thereby, ultimately determine their perceived rate of oral starch viscosity thinning.By linking genetic variation and its consequent salivary enzymatic differences to the perceptual sequellae of these variations, we show that AMY1 copy number relates to salivary amylase concentration and enzymatic activity level, which, in turn, account for individual variation in the oral perception of starch viscosity. The profound individual differences in salivary amylase levels and salivary activity may contribute significantly to individual differences in dietary starch intake and, consequently, to overall nutritional status

Oral Cooling and Carbonation Increase the Perception of Drinking and Thirst Quenching in Thirsty Adults

<div><p>Fluid ingestion is necessary for life, and thirst sensations are a prime motivator to drink. There is evidence of the influence of oropharyngeal stimulation on thirst and water intake in both animals and humans, but how those oral sensory cues impact thirst and ultimately the amount of liquid ingested is not well understood. We investigated which sensory trait(s) of a beverage influence the thirst quenching efficacy of ingested liquids and the perceived amount ingested. We deprived healthy individuals of liquid and food overnight (> 12 hours) to make them thirsty. After asking them to drink a fixed volume (400 mL) of an experimental beverage presenting one or two specific sensory traits, we determined the volume ingested of additional plain, ‘still’, room temperature water to assess their residual thirst and, by extension, the thirst-quenching properties of the experimental beverage. In a second study, participants were asked to drink the experimental beverages from an opaque container through a straw and estimate the volume ingested. We found that among several oro-sensory traits, the perceptions of coldness, induced either by cold water (thermally) or by l-menthol (chemically), and the feeling of oral carbonation, strongly enhance the thirst quenching properties of a beverage in water-deprived humans (additional water intake after the 400 ml experimental beverage was reduced by up to 50%). When blinded to the volume of liquid consumed, individual’s estimation of ingested volume is increased (~22%) by perceived oral cold and carbonation, raising the idea that cold and perhaps CO₂ induced-irritation sensations are included in how we normally encode water in the mouth and how we estimate the quantity of volume swallowed. These findings have implications for addressing inadequate hydration state in populations such as the elderly.</p></div

Estimated volume of beverages ingested when blind to the volume.

<p>Participants were asked to estimate how much they just ingested after drinking an experimental beverage presented in a lidded and opaque cup, through a straw without touching the cup. Legends and dashed lines correspond to actual volumes of the samples. Each condition was tested in triplicate. (A), Three beverages were tested: room temperature water (RT), cold water (CD) and cold carbonated water (CC). Upper panel displays ingested volumes estimated by participants and lower panel shows the time of completion to drink the whole sample. Data are represented as mean +/- SEM * indicates statistical significance at p<0.05 vs RT. (B), Participants did the same task with RT and cold water but at a forced rate (slow (10 bpm) or fast (20 bpm)). Upper panel displays ingested volumes estimated by participants and lower panel shows the time recorded to finish drinking the whole sample. Data are represented as mean +/- SEM. (n = 10 participants).</p