Application of predictive models for spoilage yeast in concentrated grape juice and wines

STURM M.E.; ARROYO-LÓPEZ F.N.; GARRIDO FERNANDEZ A.; LERENA M.C.; MERCADO L.; COMBINA M.

Recife

Jornada; V Jornadas Latinoamericanas de Biología y Biotecnología de Levaduras; 2015

Red Latinoamericana de Levaduras

Spoilage is a serious problem for concentrated grape juice and wine industries because it renders the product unacceptable and can lead to large economic losses. Zygosaccharomyces is the most frequent described spoilage yeast in concentrated juices and Dekkera bruxellensis has been described as the main spoilage yeast in red wines. To avoid these spoilage yeast two predictive models were built. The effects of pH (1.7 ? 3.2) and sugar concentration (64-68 ºBrix,) were assessed on the growth parameters of Zygosaccharomyces rouxii using response surface methodology. Experiments were carried out in concentrated grape juice inoculated with this yeast at isothermal conditions (23 ºC) and non-isothermal conditions for 60 days, trying to reproduce storage and overseas shipping temperature conditions respectively. The time to produce spoilage by Z. rouxii was obtained in both temperature conditions by the predictive model. Results show how pH was the environmental factor with the highest effect to delay the alteration of the product. Thereby, a pH value below 2.0 was enough to increase the shelf life of the product for more than 60 days in both temperature conditions. On the other hand, a probabilistic model to determine the growth/no growth interfaces of the spoilage wine yeast D. bruxellensis as a function of ethanol (10?15%, v/v), pH (3.4?4.0) and free SO2 (0?50 mg/l) using time (7, 14, 21 and 30 days) as a dummy variable was built. The model built in a simile wine medium, could have application in the winery industry to determine the wine conditions needed to inhibit the growth of this species. Thereby, at 12.5 % of ethanol and pH 3.7 for a growth probability of 0.01, it is necessary to add 48 mg/l of free SO2 to inhibit yeast growth for 30 days. Other combinations of environmental variables can also be determined. The information obtained in the present survey could be very useful for producers to predict the growth and time for spoilage of both yeasts in their respective substrates