Читать книгу Handbook of Enology: Volume 1 - Pascal Ribéreau-Gayon - Страница 37

The principal yeast species involved in grape must fermentation, particularly S. cerevisiae and S. uvarum, comprise a very large number of strains with extremely varied technological properties. The yeast strains involved during winemaking influence fermentation speed, the nature and quantity of secondary products formed during alcoholic fermentation, and the aroma characteristics of the wine. The ability to differentiate between the different strains of S. cerevisiae is required for the following fields: the ecological study of wild yeasts responsible for the spontaneous fermentation of grape must, the selection of strains presenting the best enological qualities, production and marketing controls, the verification of the implantation of selected yeasts used as yeast starter, and the constitution and maintenance of wild or selected yeast collections.

The initial research on infraspecific differentiation within S. cerevisiae attempted to distinguish strains by electrophoretic analysis of their exocellular (Bouix et al., 1981) or intracellular (Van Vuuren and Van Der Meer, 1987) proteins or glycoproteins. Other teams proposed identifying the strains by the analysis of long‐chain fatty acids using gas chromatography (Tredoux et al., 1987; Augustyn et al., 1991; Bendova et al., 1991; Rozes et al., 1992). Although these different techniques differentiate between certain strains, they are irrefutably less discriminating than genetic differentiation methods. They also present the major drawback of depending on the physiological state of the strains and on cultural conditions, which must always be identical.

In the late 1980s, owing to the development of genetics, certain techniques from molecular biology were successfully applied to characterize wine yeast strains. They are based on the clonal polymorphism of the mitochondrial and genomic DNA of S. cerevisiae and S. uvarum. These genetic methods are independent of the physiological state of the yeast, unlike the previous techniques based on the analysis of metabolism by‐products.