Nucleophilic fraction to estimate the antioxidant activity of inactivated yeast derivates

In recent years, numerous studies have been carried out at the OIV on oenological tannins, both with regard to oenological properties and methods of characterization. The results of these recent studies have led to the revision of the general monograph and the drafting of four new monographs, one for each of the four chemical classes into which the tannins have been grouped: ellagitannins, gallotannins, procyanidins/prodelphinidins, profisetinidins/prorobinetinins.

The elaboration of sparkling wine is a demanding process requiring technical as well as scientific skills. Uncovering the role of the terroir to the final product quality is of great importance for the wine market. Although the impact of the yeast strains and their metabolites on the final product quality is well documented, the action of bacteria still remains unknown. The malolactic fermentation (MLF) is carried out by the lactic acid bacteria after the alcoholic fermentation in order to ensure the microbial stability during the second fermentation that takes place in the bottle or in tanks. Oenococcus oeni is the only selected species to drive MLF that has been commercialized for sparkling wine elaboration and it is naturally present on grapes, in the cellar and also in the final product. However, whether the bacterial strain contributes to the sensory characteristics of sparkling wine is still questioned.

Botrytis cinerea, a well-known grapevine pathogen, has more than 1200 host plants causing grey rot in grapevine berries. However, it can also result in a desirable phenomenon called noble rot under specific microclimate conditions. An extraordinary demonstration of this natural process can be observed in the creation of aszú wines within Hungary’s Tokaj wine region. Beside B. cinerea other fungi and yeasts are involved in the secondary metabolic development of the grape berry which contributes to the sensory and analytical characterization of noble rot wines.

During 1982 started our wine growing project at the Puntalarga Hill, between 2500 and 2600 meters a.s.l.: 5.78 ºN, 72.98 ºW. Pinot noir, white Riesling and Riesling x Silvaner crossings are the most planted grapevines. Since 1984 research and development activities are carried out on pertinent subjects.

Primary and secondary metabolites are major components of grape quality and wine typicity. Their accumulation is interconnected through a complex metabolic network, which is still not well understood. This study aims to investigate how the enzymes of central carbon metabolism interact with anthocyanin biosynthesis during grape berry development: does the accumulation of anthocyanins, which represents a non-negligible diversion of carbon metabolic fluxes, require reprogramming of central enzymes or is it controlled downstream of central metabolism? To this end, 23 enzymes involved in central carbon metabolism pathways have been analyzed in the berries of 3 grape cultivars, which have close genetic background but distinct temporal dynamics of anthocyanin accumulation.