Beer-Spoiling Yeasts: Genomics, Detection, and Control
Chris D. Powell and Daniel W.M. Kerruish
from: Brewing Microbiology: Current Research, Omics and Microbial Ecology (Edited by: Nicholas A. Bokulich and Charles W. Bamforth). Caister Academic Press, U.K. (2017) Pages: 289-328.
Beer-spoiling yeasts comprise a diverse group of organisms that can have a variety of impacts on beer production. Invariably, contamination of wort or beer by these yeasts leads to inconsistencies within the process, and quality defects in packaged beer. Beer-spoiling yeasts can be broadly separated into non-fermentative (aerobic) and fermentative yeasts. The former typically exploit process steps associated with raw materials, and areas where oxygen ingress is difficult to prevent, such as unpasteurized cask beers or dispense. Fermentative yeasts are arguably more problematic due to their capacity to compete with production strains during fermentation. Major impacts include altered sugar utilisation, flocculation and ethanol production, as well as the formation of phenolic compounds, acidity, estery off-flavours, and haze or turbidity. These effects occur primarily due to differences in the genetic, metabolic and physiological characteristics of the spoilage yeast and the production strain. In this chapter, we describe the characteristics and functionality of beer-spoiling yeasts, as well as methods for their isolation and identification read more ...