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 been recently 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 was never investigated. This investigation aimed to op-timize quality of beers fermented by an oenological Schizosaccharomyces pombe strain alterna-tively combined with two S. cerevisiae strains (WB06, commercial; 9502, of oenological origin). The influence of both in-bottle refermentation (alternatively carried out by one of the two Sac-charomyces cerevisiae strains used in the sequential first fermentation) and starchy ingredient (three mixtures of 65%-malted barley alternatively combined with 35%-unmalted common, du-rum, or emmer wheat) was studied. Beer formulation was optimized through a 2-factor mixed 3- and 2-level design, where the two factors were the starchy ingredient 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 greatest 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 physico-chemical and 14 sensory characteristics, with R2 often higher than 0.9.