EFFECT OF ENVIRONMENTAL CONDITIONS ON FLOCCULATION AND IMMOBILISATION OF BREWER'S YEAST DURING PRODUCTION OF ALCOHOL-FREE BEER

Abstract

A method using immobilised yeasts has been developed and successfully applied for production of alcohol-free beer. The influence of environmental conditions present during alcohol-free beer production on the flocculation and immobilisation of the yeast Saccharomyces cerevisiae var. uvarum was investigated in the present study. In wort, the cells developed flocculation at the end of exponential growth, according to the NewFlo phenotype. In defined medium, the flocculation capacity appeared to be temporary and was lost rapidly during the stationary phase. No increase in cell wall hydrophobicity at the onset of flocculation was observed in either medium. Low growth temperatures increased flocculation capacity approximately four-fold, compared to growth at high temperatures. The optimum temperature for flocculation was at 25°C with cells grown at low or high temperature. A novel method using carboxyfluorescein-stained cells was developed to analyse the initial adhesion of cells to carrier. This method also allowed rapid analysis of the effects of immobilisation to DEAE-cellulose carrier during alcohol-free beer production process. It appeared that a high flocculation capacity stimulated adhesion to the DEAE-carrier.