Yeasts and their possible beneficial and negative effects on the quality of dairy products

Abstract

This review deals with yeasts and their potential use as starter cultures in dairy products as well as their role as spoilage organisms. The taxonomy of relevant yeasts is described, with emphasis on molecular techniques and simplified identification systems applicable to industry. Quantitative assessment of undesirable yeast contamination is discussed with regard to present requirements for quality assurance in dairies. Special attention is given to the role of yeasts in the complex microbial interactions prevailing in several dairy products and to controlling fermentation, maturation and important product characteristics. Antimicrobial activities of yeasts, including secretion of ‘killer factors’ with broad antimicrobial spectra are linked with the reported probiotic starter cultures. The desired properties of yeasts to be used as starter cultures in the dairy industry are summarized and areas of research are proposed to gain the insight required to obtain full advantage of the active use of yeast cultures in a wider range of products.