PREDICTION OF THE FERMENTATION PERFORMANCE OF BREWING YEAST WITH THE ACIDIFICATION POWER TEST

Abstract

Fermentation performance (defined as the time required, in hours, to attenuate an all malt wort from OG 1040° to 1020°) can be accurately predicted for Saccharomyces cerevisiae NCYC 1681 using the Acidification Power test (r =0.943, p = <0.001: 37 samples). The results obtained with four other yeasts suggest that the test has wide applicability. The test measures the ability of a population of yeast cells to maintain different intracellular and extracellular hydrogen ion concentrations when placed in distilled water. It also measures the change in these concentrations induced by the presence of glucose. The method is reproducible (standard deviation of the mean =0.61 %) and is unaffected by variations of ±11 % of yeast weight in the assay, this makes the Acidification Power test a ‘stand alone’ test, no secondary analyses (such as dry weight determination) are necessary. The test can be performed using common laboratory equipment and can be applied routinely in breweries for yeast selection based on the use of Reject Quality Limits (RQL). In addition, the technique may find application in the evaluation of yeast handling protocols, in the assessment of new or novel yeast strains, and in the assessment of yeast condition prior to acid washing.