Room and low temperature brewing with yeast immobilized on gluten pellets

A biocatalyst prepared by the immobilization of a cryotolerant strain of Saccharomyces cerevisiae on gluten pellets was used for batch and continuous fermentation at low temperatures. The immobilized yeast showed important operational stability in repeated batch fermentations without a decrease of activity even at 0 and 5 degrees C. Repeated batch fermentations using the biocatalyst resulted in improvement of ethanol productivity in comparison with bottom brewing fermentation and free cells using the same yeast strain. At 0 and 10 degrees C, the fermentation rate was four and seven times higher than that of free cells, respectively. For immobilized yeast, diacetyl and polyphenol contents were lower and the alcohol concentration higher at low temperatures (0-7 degrees C) when compared to free cells. Fine clarity was also observed in the beers. Continuous brewing using gluten-supported biocatalyst had an operational stability of 3 months with relatively high productivity and without contamination. Polyphenol and bitterness contents were lower in the continuous process than those of batch fermentations, but at low temperature (5 degrees C) they were higher. The diacetyl content was higher than in batch fermentations and beers had a fine aroma and taste. (C) 1997 Elsevier Science Ltd.