Effect of post-harvest ozone treatment on secondary metabolites biosynthesis and accumulation in grapes and wine

Wine lees are quantitatively the second most important wine by-product after grape stems and marc [1]. In order to recycle, distilleries recovered ethanol and tartaric acid contained in wine lees but yeast biomass is often unused. It has already been demonstrated that this yeast biomass could be upcycled to produce yeast extracts of interest for wine chemical stabilization [2]. In addition, it is well known that lees, during aging, release compounds that preserve wine from oxidation.

Atypical ageing (ATA) is a wine aroma fault occurring in white wines characterised by an early loss of varietal aroma as well as nuances of wet mop, acacia blossom, shoe polish and dirty rag among others. 2-aminoacetophenone (2AAP) – a degradation product of indole-3-acetic acid (IAA) – has been described as the major odour-active compound and chemical marker responsible for this off-flavour. Depending on the aroma intensity of wines, its odour threshold varies from 0.5 to 10.5 μg/L. It seems that a stress reaction in the vineyard triggered by climatic, pedological and viticultural factors can ultimately cause ATA development in wines and therefore shorten their shelf-life.

Mannoproteins are released at the end of alcoholic fermentation due to yeast autolysis [1]. It has been described a positive effect of these molecules on lactic acid bacteria growth [2]. The main objective of this work was the characterization of different mannoproteins extracted from active dry yeast (ADY) and the assessment of their effect on Oenococcus oeni and malolactic fermentation (MLF).

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.

Viticulture’s adaptation to the harmful effects of climate change is globally the biggest challenge of the near future. Short, extremely intensive rainfalls and longer periods of drought are getting more frequent in the Tokaj Wine Region, where the majority of the vineyards are cultivated on steep slopes. Hence, erosion has high risk, especially when combined with the loess-based soils on about ten percent of the region. The environmentally beneficial cover crop and mulch usage can effectively reduce the risk of erosion, according to research done by the Tokaj Wine Region Research Institute of Viticulture and Oenology.