Bioprotection of musts and wines from white grapes of the Muscat variety as an alternative to sulfur dioxide; use of commercial non-Saccharomyces yeasts with sequential inoculation strategies.

Identifier:  TFG:9293

Handle: https://hdl.handle.net/20.500.11797/TFG9293

Authors:  Santacana Bolet, Joan

Abstract:
Enzymatic browning is a biochemical process in which orthodiphenols oxidize and condense, consequently changing the color of the wine to brown tones. This oxidative process becomes a major problem in white wines. The universal tool used to prevent browning is sulfur dioxide, which has antioxidant, antioxidative and antiseptic properties. Despite being a very necessary and complete additive, its use is increasingly problematic due to being an allergen that can cause health problems. Therefore, different tools have been proposed as an alternative to sulfur dioxide, one of which is bioprotection. This tool, through the coinoculation or sequential inoculation of different species of yeast or bacteria, aims to control the development of unwanted microorganisms and protect the wine from oxidation. In this study, yeast strains of the species Lachancea thermotolerans, Metschnikowia pulcherrima and Torulaspora delbrueckii have been sequentially inoculated in three wines at a dose of 2 g/hl of sulfur dioxide, 48 hours before Saccharomyces cerevisiae, in order to compare with 2 control conditions, at 2 and 5 g/hl of sulfur dioxide and with conventional inoculation with Saccharomyces cerevisiae. Different physicochemical parameters have been analyzed from the resulting wines. From the analyzes carried out, it has been determined that the condition inoculated with Lachancea thermotolerans has generated 2.8 g/l of lactic acid, has generated a smaller amount of acetic acid and has preserved malic acid, inhibiting malolactic fermentation, thus acting as a bioprotector. The conditions inoculated with Metschnikowia pulcherrima and Torulaspora delbrueckii have shown a degradation of malic acid and, therefore, have carried out malolactic fermentation. Regarding browning, the colorimetric parameters have been analyzed and it has been determined that the conditions using sequential inoculation with non-Saccharomyces yeasts show less browning compared to the controls. However, it has been determined that the conditions with sequential inoculation have shown higher concentrations of polysaccharides and proteins compared to the control. In conclusion, the sequential inoculation of the three species of non-Saccharomyces yeast have been effective in terms of browning the color of the wine. In addition, Lachancea thermotolerans has shown inhibitory capacity against lactic acid bacteria. Therefore, sequential inoculations with the non-Sacchamromyces yeast species studied is a useful biotechnological tool to reduce sulfur dioxide doses.