Wine lees: characterization and valorization by kombucha fermentation

Winemaking generates various types of residues (vine shoots, stalks, pomace, wine lees and filtration cakes) which can have a notable environmental and economic impact. Wine by-products are rich in bioactive compounds and therefore their valorization can be beneficial on different levels. Lees are the material that settles after vinification, and consist mainly of yeast cells, grape skins, tartrates, phenolic compounds, and other residues. The objective of this study was to valorize the wine lees by the Kombucha process in order to create a new beverage. 

Kombucha is a traditional beverage obtained by the fermentation of sweetened tea with a symbiotic culture of yeast and bacteria. The consumption of kombucha is associated with many health benefits due to its rich composition in bioactive compounds. Different substrates were used as raw material for Kombucha fermentation, and the obtained beverages displayed an increase in the concentration of biological compounds and enhancement of health activities. 

Red wine lees used in this study presented a pH of 3.31 ± 0.01, a total acidity of 2.86 ± 0.45 g/L (sulfuric acid equivalent), a total polyphenol content of 2041 ± 233.35 mg/L GAE (Gallic acid equivalent), and an antioxidant activity of 59.03 ± 4.25 % inhibition against DPPH radicals. 

In order to ferment the wines lees by Kombucha Scoby, wine lees were subject to two dilutions of 1:2 and 1:4. These dilutions were fermented for 24 days at 25°C. Samples were taken each 3 days in order to monitor the physico-chemical evolution of the new beverage. Results showed that the sugar consumption (70 g/L) was not complete after 24 days of fermentation. pH of the new beverage is 2.88. Fermentation time and substrate concentration influenced the studied variables, for instance the strongest antioxidant activity was detected on the 9th day for the lees kombucha diluted to the half (93.27%) whereas the highest quantity of polyphenols was found on day 21 (1599.30 mg/L GAE).

Presenting author: Youssef El Rayess – Department of Agriculture and Food Engineering, Holy spirit University of Kaslik, Jounieh, Lebanon

Additionnal authors: Nathalie Barakat | Laboratoire de Génie Chimique, Université de Toulouse, CNRS, INPT, UPS, Toulouse, France, Sandra Beaufort | Laboratoire de Génie Chimique, Université de Toulouse, CNRS, INPT, UPS, Toulouse, France, Samar Azzi-Achkouty | Department of Agriculture and Food Engineering, School of Engineering, Holy Spirit University of Kaslik, Jounieh, Lebanon, Ziad Rizk | Lebanese Agricultural Research Institute, Fanar Station, P.O. Box 90-1965, Jdeidet El-Metn, Fanar, Lebanon, Chantal Ghanem | Lebanese Agricultural Research Institute, Fanar Station, P.O. Box 90-1965, Jdeidet El-Metn, Fanar, Lebanon, Abdo Tannoury | Lebanese Agricultural Research Institute, Fanar Station, P.O. Box 90-1965, Jdeidet El-Metn, Fanar, Lebanon, Jalloul Bouajila | Laboratoire de Génie Chimique, Université de Toulouse, CNRS, INPT, UPS, Toulouse, France, Patricia Taillandier | Laboratoire de Génie Chimique, Université de Toulouse, CNRS, INPT, UPS, Toulouse, France, Youssef El Rayess | Department of Agriculture and Food Engineering, School of Engineering, Holy Spirit University of Kaslik, Jounieh, Lebanon 

Email: youssefrayess@usek.edu.lb

Keywords: wine lees-Kombucha-polyphenols-antioxidants

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