Selection of native yeast of Calchaqui Salteño Valley for Torrontes wine

Abstract

The Torrontés Riojano is an emblematic variety in the Calchaquí Salteño Valley. The obtaining of selected native yeasts is a tool of differentiation of the wines, highlighting unique characteristics of the terroir. Native yeasts were isolated from spontaneous fermentations of Torrontés grapes harvested in nine zones of the Valley. We obtained 45 isolates. Three fermentations were chosen for their sensorial profile, of which 13 strains were analyzed for their macro and microscopic characteristics and molecular biology. We studied the production of hydrogen sulphide and the fermentation efficiency of some isolates compared to two commercial reference strains. Micro-vinifications with Saccharomyces cerevisiae were selected based on their distinctive oenological characteristics, as compared to a commercial strain and spontaneous fermentation. The wines obtained were analyzed chemically and sensorially. Fifteen strains were analyzed by interdelta PCR, 8 molecular patterns were obtained, 2 correspond to commercial strains and 1 non-amplified. In the efficiency study, the native strain F9-3 presented a fermentation rate (2.38 g CO₂/d) significantly higher than all strains studied. The native strain F9-5 presented the highest fermentation yield (16.33 AR / Et) and produced the highest concentration of alcohol (13.35%v/v). The strains EC1118, F9-5 and F6-7 presented similar fermentative vigor and were significantly superior to the other strains. In the sensory evaluation, the wine of strain F9-5 obtained a better score in its overall impression and was preferred by 47% of experts.