ACIDIC AND DEMALIC SACCHAROMYCES CEREVISIAE STRAINS FOR MANAGING PROBLEMS OF ACIDITY DURING THE ALCOHOLIC FERMENTATION

Haze formation in wine during transportation and storage is an important issue for winemakers, since turbid wines are unacceptable for sale. Such haze often results from aggregation of unstable grape proteinaceous colloids. To date, foreseeably unstable wines need to be treated with bentonite to remove these, while excessive quantities, which are often required, affect the wine volume and quality (Cosme et al. 2020). One solution to avoid these drawbacks might be the use of peptidases. Marangon et al. (2012) reported that Aspergillopepsins I and II were able to hydrolyse the respective haze-relevant proteins in combination with a flash pasteurisation. In 2021, the OIV approved this enzymatic treatment for wine stabilisation (OIV-OENO 541A and 541B).

Malolactic fermentation (MLF) is a desired process to decrease acidity in wine. This fermentation, carried out mostly by Oenococcus oeni, is sometimes challenging due to the wine stress factors affecting this lactic acid bacterium. Wine is a harsh environment for microbial survival due to the presence of ethanol and the low pH, and with limited nutrients that compromise O. oeni development. This may result in slow or stuck fermentations. After the alcoholic fermentation the nutrients that remain in the medium, mainly released by yeast, can be used in a beneficial way by O. oeni during MLF.

Smoke taint (ST) is a grape-wine off-flavour that may occur when grapes absorb volatile phenols (VPs) originating from wildfire smoke (1). ST is associated with the negative sensory attributes such as smoky and ashy notes. VPs are glycosylated in the plant and thus present in both free and bound forms (2; 3). Wildfire smoke has resulted in a decline in grape and wine quality and financial losses which has become a prominent issue for the global wine industry.

With the development of naturality expectations, wines produced without any addition of sulfur dioxide (SO₂) become very popular for consumers and such wines are increasingly present on the market. Recent studies also showed that Bordeaux red wines without added SO₂ could be differentiated from a sensory point of view from similar wines produced with SO₂¹. Thus, the aim of the current study was to characterize from a sensory point of view, specific aromas of wines without added SO₂ and to identify compounds involved.

Wine grape pomace quantitatively and qualitatively represents the most important fraction of wine waste. Namely, this by-product makes ~ 20% of the total mass of vinified grapes, and it is characterized with high concentrations of polyphenolic antioxidants, as well as grape seed oil. Hence, valorization of wine pomace, as an alternative to traditionally employed disposal, has drown considerable interest in recent years. Earlier studies were mostly focused on the extraction of phenolics, while mechanisms enhancing the extraction of lipid fraction from grape pomace, as well as their impact on the grape seed oil quality are far less investigated.