Application of yeast and bacteria as starter cultures

Abstract

The two main organisms involved in vinification Saccharomyces cerevisiae and Oenococcus oeni are somewhat unusual in selectively employing fermentative metabolism. They are also atypical in withstanding higher alcohol concentrations. Yeast are significant in winemaking because they carry out the alcoholic fermentation, causing the change from grape juice to wine by their metabolic activity as it was demonstrated by Louis Pasteur 1866. Besides having a major effect on the sugar content of juice or must yeast produces the most important wine volatiles, notably higher alcohols, fatty acids, and esters. Via its enzymatic properties it can also liberate grape derived bound aroma compounds. To a minor extend the statement above is also valuable for the wine lactic acid bacteria responsible for the malolactic fermentation. Malolactic fermentation is not only the simple decarboxylation of malic acid to lactic acid and CO2 resulting in a decrease of the total wine acidity. Utilizing wine as a substrate for growth, malolactic bacteria will remove some wine constituents and will produce others as a result of their metabolism. The metabolic activity of the MLB influences the aroma compounds of wine that are derived from fruit and the alcoholic fermentation, and it also confers biological stability upon the final product. © 2009 Springer-Verlag Berlin Heidelberg. All rights reserved.