MICROFLUIDIC PLATFORM FOR SORTING YEAST CELLS ACCORDING TO THEIR MORPHOLOGY

In a recent study several genes controlling the acidification properties of the wine yeast Saccharomyces cerevisiae have been identified by a QTL approach [1]. Many of these genes showed allelic variations that affect the metabolism of malic acid and the pH homeostasis during the alcoholic fermentation. Such alleles have been used for driving genetic selection of new S. cerevisiae starters that may conversely acidify or deacidify the wine by producing or consuming large amount of malic acid [2]. This particular feature drastically modulates the final pH of wine with difference of 0.5 units between the two groups.

Red wine ageing is an important step in the red wine evolution and impacts its chemical and sensory characteristics through many chemicals and physico-chemical reactions. The kinetics of these evolutions depend on the wine studied and influence the wine ageing potential. Generally, high quality red wines require a longer period of bottle ageing before consumption¹. The ageing potential is an impor-tant parameter for wine quality and is related to the capacity of a wine to undergo oxidation over time². Phenolic compounds which are ones of the main substrates for oxidation can then potentially modulate ageing potential³.

The effects of (A) grape freezing, and (B) malolactic fermentation, have been evaluated on the chemical and colorimetric profiles of red wines from Schiava grossa cv. grapes, thus prone to colour instability. The aim was to observe if specific variables (e.g. grape freezing) could improve the extraction and stability of pigments. The samples were studied from musts up to twelve months in bottle. The study was conducted with independent parallel micro-vinifications (12 = 4 theses x 3 replicates) under strictly-controlled conditions.

Color is one of the key elements for the marketing of rosé wines due to their packaging in transparent bottles. Their broad color range is due to the presence of pigments belonging to phenolic compounds extracted from grapes or formed during the wine-making process. However, the mechanisms responsible for such diversity are poorly understood. The few investigations performed on rosé wines showed that their phenolic composition is highly variable, close to that of red wines for the darkest rosés but very different for light ones [1]. Moreover, large variations in the extent of color loss taking place during fermentation have been reported but the mechanisms involved and causes of such variability are unknown.

It is well known that the vinification of grapes at full maturation can produce rich, full-bodied wines,
with intense and complex flavour profiles. However, the juice obtained from such grapes may have very
high sugar concentration, resulting in wines with an excessive concentration of ethanol. In addition, the decoupling between technological maturity and phenolic/aromatic one due to global warming, exacerbates this problem in some wine-growing regions. In parallel with the increase of the mean alcohol content of wines on the market, also the demand for reduced alcohol beverages has increased in recent years, mainly as a result of health and social concerns about the risks related to the consumption of alcohol.