Yeast selection for the production of novel “mixed-fruit wines”

Statistics of the global wine consumption has shown that Europe is consuming less and less wine and, on the market, have been appearing new alternatives of wine that are inexpensive and easy drinking, such as the “flavored” wines with low alcohol content and obtained blending wines and fruit juices or flavoring wine with artificial or natural aromas. Although there is an ancient art to obtain fruit wines (not grape-based), no literature is available regarding the production of beverages that are obtained by the co-fermentation of grape and fruit. The formulation of new mixed-fruit wines could represent the basis for reducing post-harvest fruit losses and contribute to the economy of the existing wine industry. For this purpose, the selection of useful yeasts is advised to drive the alcoholic fermentation (AF) and, meantime, to enrich the final wines in active bio-functional compounds such as glutathione, resveratrol, melatonin, etc. Must fermentations were carried out inoculating Saccharomyces cerevisiae EC1118, a commercial wine yeast, in four musts obtained by blending grape must (Chardonnay and Cabernet Sauvignon) and strawberry fresh juice at two different proportion, 80:20 and 60:40. The AF was daily monitored by weight loss and until weight stabilization for 48h. S. cerevisiae EC1118 was able to exhaust the available sugars in all trials in 144h from the inoculum, as a maximum. In comparison to a theoretical alcoholic degree of about 15% and 11.5% (v/v) (calculated from the initial sugar concentration of the red and white grape musts alone, respectively), a significant reduction of ethanol was obtained in the mixed-fruit wines. In particular, on the basis of grape:strawberry proportion, alcohol was 3-4.5% less in wines prepared with red grape and 6-7% (v/v) less in case of white grape. Only negligible difference was found for the pH. The total acidity was higher for mixed-fruit wines obtained with must from red grape as higher concentrations of organic acids, namely tartaric, malic and citric, were found. The higher levels of citric acid detected for the proportion 60:40 could protect the wine components, bio-functional compounds included, against the oxidation. Torulaspora delbruekii showed a good fermentation performance as well, suggesting its potential use as starter yeast.