CHARACTERIZATION AND IDENTIFICATION OF YEAST BIOACTIVE PEPTIDES RELEASED DURING FERMENTATION AND AUTOLYSIS IN MODEL WINE

Right after the pouring of wine in a glass, a myriad of volatile organic compounds, including ethanol, overwhelm the glass headspace, thus causing the so-called wine’s bouquet [1]. Otherwise, it is worth noting that during wine tasting, most people automatically swirl their glass to enhance the release of aromas in the glass headspace [1]. About a decade ago, Swiss researchers revealed the complex fluid mechanics underlying wine swirling [2]. However, despite mechanically repeated throughout wine tasting, the consequences of glass swirling on the chemical space found in the headspace of wine glasses are still barely known.

Grape pomace is one of the main by-products generated after pressing in winemaking.Emerging methods, such as ultrasound-assisted extraction with eutectic mixtures, have great potential due to their low toxicity, and high biodegradability. Choline chloride (ChCl) was used as a hydrogen bond acceptor and its corresponding hydrogen bond donor (malic acid, citric acid, and glycerol: urea). Components were heated at 80 °C and stirred until a clear liquid was obtained. Distilled water was added (30 % v/v). A solid-liquid ratio of 1 g pomace per 10 ml of eutectic solvent was used.

Yeast co-inoculations in winemaking have been investigated in various applications, but most often in the context of modulating the aromatic profiles of wines. Our study aimed to characterize S. cerevisiae interactions and their impact on wine by taking an integrative approach. Three cocultures and corresponding pure cultures of S. cerevisiae were characterized according to their fermentative capacities, the chemical composition and aromatic profile of the associated Chardonnay wines. The various strains studied within the cocultures showed different behaviors regarding their development.

Wine regions are getting warmer as average temperatures continue raising affecting grape growth, berry composition and wine production. Berry quality was evaluated in plants of Vitis vinifera cv Syrah grafted on two rootstocks, Paulsen (PL1103) and SO4, and grown under two salinity concentrations (LS:0.7dS/m and HS:2.5dSm-1) in combination with two irrigation regimes (HW:133% and CW:100%), being the seasonal water application 483mm (control, 100%). Spectrophotometer measurements from berry skin during veraison and harvest stages and from “young” wine samples, were indicative of the stressors effect and the mediation of the rootstocks. At veraison (i) total phenolics content were high under LSHW (0.7dSm-1 and high water conditions) for SO4 and PL1103.

During alcoholic fermentation, nitrogen is one of essential nutrient for yeast as it plays a key role in sugar transport and biosynthesis of and wine aromatic compounds (thiols, esters, higher alcohols). The main issue of a lack in yeast assimilable nitrogen (YAN) in winemaking is sluggish or stuck fermentations promoting the growth of alteration species and leads to economic losses. Currently, grape musts are often characterized by low YAN concentration and an increase of sugars concentration due to global warming, making alcoholic fermentations even more difficult. YAN depletion can be corrected by addition of inorganic (ammonia) or organic (yeast derivatives products) nitrogen during alcoholic fermentation.