Evaluation of autochthonous Saccharomyces bayanus strains under stress conditions for making ice ciders

- A method for screening of yeast strains to be used under stress conditions is proposed.
- Synthetic media could discriminate yeasts by their ability to grow and ferment sugars.
- Ten indigenous yeast strains have been selected for the making of good quality ice ciders.

The product diversification policy being carried out by the Asturian cider industry includes the development of beverages similar to so-called ice ciders. During apple juice fermentations, yeast cells are affected by several stress conditions. In this study, 74 Saccharomyces bayanus strains isolated from Asturian cider, have been analyzed in synthetic media for their growth ability, sugar fermentation capacity and acetic acid production under the stress conditions that occurr during the production of ice cider. According to the data obtained 23 strains high proliferation capabilities, sugar fermentation capacity and low acetic acid production have been differentiated. Ten strains were chosen to produce ice ciders from apple juice (31.8 ºBrix) at 12 °C. The products obtained were characterized by not having developed the malolactic conversion and their low contents of acetic acid, methanol and ethyl acetate. Significant differences among ciders were detected for alcoholic degree, total acidity, and contents of glycerol, pyruvic, fumaric and shikimic acids due to the yeast strain used. A Multiple Correspondence Analysis showed four strains associated with sensory quality variables. Our results open up the possibility of using autochthonous S. bayanus strains as starters in the making of Asturian ice ciders.