Interaction between the enzymes of central carbon metabolism and anthocyanin biosynthesis during grape berry development

Around the world, the alcohol content of wine has been steadily increasing; partly as a consequence of climate change, but also due to improvements in viticultural management practices and winemaking techniques [1,2]. Concurrently, market demand for wines with lower alcohol levels has increased as consumers seek to reduce alcohol intake for social and/or health reasons [3]. As such, there is increasing demand for both innovative methods that allow winemakers to produce ‘reduced alcohol wines’ (RAW) and a better understanding of the impact of such methods on the composition of RAW. This study therefore aimed to investigate compositional changes in two red wines resulting from partial alcohol removal following treatment by one such method, involving a combination of reverse osmosis and evaporative perstraction (RO-EP).

Maturation of wine on lees (often referred as sur lie) is a common practice applied by many winemakers around the world. In the past this method was applied mainly on white and/or sparkling wine production but recently also to red wine production. In our experiment, we matured red wine on wine lees of two origins: a) Light wine lees, collected after the completion of the alcoholic fermentation, b) Heavy lees, collected after the completion of the malolactic fermentation. The lees were free of off-odors and were added in the red wine in percentage 3% and 8%, simulating common winemaking addition. The maturation lasted in total six months and samples were collected for analysis after one, three and six months. During storage the lees were stirred.

Cabernet Sauvignon is one of the most important winegrape varieties in Chile. However, temperature raise and decreased rainfall due to climate change can lead to grape quality decrease in certain areas. Amino acids are essential as nitrogen source for yeast but also directly affect grape quality serving as precursors of certain volatile compounds that enhance the wine bouquet. Besides, glutathione is an important tripeptide acting as antioxidant, preventing the appearance of browning pigments in must and exerts a protective effect in volatile compounds.

Not only vintner’s decisions in the vineyard, but also winemaker’s choices of technology approaches in the cellar play a significant role in the final wine style and quality. Whereas traditional technologies within chosen terroir are quite well explored and thus somehow predictable, there is no proper knowledge available on possible outcomes in case of implementing novel, alternative winemaking strategies. To reveal their effects on wine aroma compounds and sensory characteristics, two alternative strategies
(cryoextraction or addition of whole grape berries during last stages of fermentation) were compared to classical Vipava valley winemaking approach as normally used for an autochthonous variety Zelen. After separate vinification and bottling, all the experimental wines were subjected to semiquantitative metabolic profiling of volatile compounds (VOCs) by means of GC/MS and were then also sensorialy evaluated by pre-trained panel.

Wine color is one of the main organoleptic characteristics influencing its quality. It is of especial interest in red vinifications due to the economic resources that wineries have to invest for the extraction of the phenolic compounds responsible of wine color, compounds that are mainly located inside the skin cell vacuoles. Moreover, these phenolic compounds not only influence color but also other organoleptic properties such as body, mouthfeel, astringency and flavour. The transference of phenolic compounds from grapes to must during vinification is closely related with the type of grapes and the winemaking technique.