The inhibition of Saccharomyces cerevisiae population during alcoholic fermentation of grape must by octanoic, decanoic and dodecanoic acid mixture

Department of Viticulture and Enology, Faculty of Horticulture, Mendel University in Brno, Valticka 337, CZ-691 44 Lednice, Czech Republic

Abstract

The inhibition of alcoholic fermentation by octanoic, decanoic and dodecanoic acid mixture was investigated. Middle chain fatty acids (MCFA) mixture contained 10 grams of C₈:C₁₀:C₁₂ in a ratio of 2:7:1 was dissolved in 100 ml of 70% ethanol, and in such form, it was subsequently applied into the fermenting must samples. A flow cytometry test showed that the 10 mg/L dose of MCFA mixture had a toxic effect on Saccharomyces cerevisiae (45.9% of viable cells) compared with the control variant (74.35%). In combination with 60 mg/L of SO₂, it had a higher efficiency (3.1% of viable cells) than using a dose of SO₂ alone (13.9%). Direct counting of yeast cells confirmed a higher concentration of dead cells with a higher concentration of MCFA. A dose of 10 mg/L of MCFA mixture caused the highest percentage of dead yeast after 24 hours (about 60%) compared to the control variant without MCFA dosage (about 24%). The results of residues showed that there is no significant quantitative difference between the treated and untreated musts because of fixing of MCFA inside the yeast cells. This method can effectively reduce the cost of production technology for wines with residual sugar and, in general, reduce the dosage of SO₂.