6/1/2023 0 Comments K and l wines![]() Acetaldehyde accumulation differs according to yeast species and strain, ranging from 0.5 for the least productive ones to more than 700 mg/L for the most productive ones. Indeed, during alcoholic fermentation under reducing conditions, acetaldehyde is the most important carbonyl compound produced by yeasts after ethanol. The acetaldehyde in wines has microbiological and/or chemical origins. These high concentrations of acetaldehyde give undesired organoleptic properties to wines, such as green apple, freshly cut grass and nutty aromas, which, however, are sometimes sought after in particular, in wines such as “vins jaunes”. At low concentrations, acetaldehyde has a pleasant and fruity aroma, while at high levels, its odor becomes irritating and pungent, which depreciates the organoleptic qualities of wines for consumers. The concentration of total acetaldehyde in wines generally varies between 10 and 200 mg/L, with a sensory perception threshold of around 100 to 125 mg/L for free acetaldehyde. Typically, in the presence of sulfite, the combination rate is 50–60% at the end of fermentation. In wine, free acetaldehyde can form more or less stable combinations with other molecules to produce combined or bound acetaldehyde the sum of the free and combined acetaldehyde corresponds to the total acetaldehyde. Acetaldehyde, also referred to as ethanal or acetic aldehyde, is a powerful aromatic compound that can be found in many food matrices: apple juice, spirits, beer, cider, wine, cheese, yogurt and butter. The main reaction in this biological process is the bioconversion of sugars into ethanol and carbon dioxide, as well as many other compounds responsible for the organoleptic profile of the wine. Thanks to the use of production balances, it was possible to determine that the decrease in acetaldehyde concentration during the stationary phase was mainly due to yeast consumption, which was explained by the metabolic links found between acetaldehyde and markers of metabolism, such as organic acids.Īlcoholic fermentation is the central stage of the wine-making process using the yeast Saccharomyces cerevisiae. Physical evaporation was more important at high temperatures, reinforcing the final decrease in acetaldehyde concentration. ![]() From a biological point of view, the high fermentation temperatures led to important production of acetaldehyde at the end of the growth phase but also allowed better consumption of the molecule by yeast. ![]() Thanks to new online monitoring approaches, anisothermal temperature management and associated mathematical methods, complete acetaldehyde production balances during fermentation made it possible to dissociate biological consumption from physical evaporation. One recurrent question about this molecule is: can temperature both increase and decrease the consumption of the molecule by yeast or does it only promote its evaporation? Therefore, the main objective of this study was to describe and analyze the evolution of acetaldehyde and shed light on the effect of temperature, the main parameter that impacts fermentation kinetics and the dynamics of acetaldehyde synthesis. ![]() The compound acetaldehyde has complex synthesis kinetics since it accumulates during the growth phase and is consumed by yeast during the stationary phase, as well as evaporating (low boiling point) throughout the process.
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