DISINFECTION OF BREWING YEAST WITH ACIDIFIED AMMONIUM PERSULPHATE

Abstract

Acidified (pH 2.8) ammonium persulphate (0.75%) was more effective than an acid wash at pH 2.8 or straight 0.75% ammonium persulphate in the disinfection of contaminated yeasts obtained from breweries. The contaminating bacteria in the samples of brewery yeast were isolated and grown in mixed fermentations with yeast. The data from disinfection trials with the contaminated yeasts showed that acidified ammonium persulphate provided the most effective treatment. The following patterns of bacterial resistance to the various treatments were noted: (a) lactobacilli tend to be resistant to disinfection with 0.75% ammonium persulphate; (b) acetic acid bacteria resist acid treatments, unless the pH is 2.4 or lower; and (c) flavobacteria are sensitive to acid washes and to treatments with ammonium persulphate, but the acidified ammonium persulphate killed this bacterial type more rapidly.