Witbier Fermented by Sequential Inoculation of Schizosaccharomyces pombe and Saccharomyces cerevisiae: Influence of Starchy Ingredients and S. cerevisiae Strain Used for In-Bottle Refermentation

Great attention has recently been dedicated to the use of non-Saccharomyces yeast strains for the development of new beer formulations. However, the effect of the Saccharomyces strain used in the refermentation of this type of beer has never been investigated. The research described aimed to optimize the quality of beers fermented by an oenological Schizosaccharomyces pombe strain alternately combined with two S. cerevisiae strains (WB06, commercial; 9502, of an oenological origin). The influence of both in-bottle refermentation (alternately carried out by one of the two Saccharomyces cerevisiae strains used in the sequential first fermentation) and starchy ingredients (three mixtures of 65% of malted barley alternately combined with 35% of unmalted common, durum, or emmer wheat) was studied. The beer formulation was optimized through a two-factor mixed three- and two-level design, where the two factors were the starchy ingredients and the refermenting S. cerevisiae. Beers from durum wheat beers refermented by WB06 had the highest alcohol contents. Common wheat beers refermented by 9502 showed the highest antioxidant activity values. The highest overall sensory score was assigned to the beers refermented by 9502. The fitted quadratic model had a good predictive ability for five physicochemical and fourteen sensory characteristics, with an R2 often higher than 0.9.