The interaction between yeasts and bacteria in dairy environments

The general environment from which raw dairy products originate and the mic robiological quality of the products in its processed state inevitably admi t yeast growth and spoilage. Only part of the primary microflora. survives under the selective pressures exerted by the intrinsic and extrinsic biotic factors present, processing procedures and preservatives. Yeasts that poss ess the proper physiological attributes to counteract the specific ecologic al determinants will be favored. Eventually, a particular yeast community w ill develop, and if the environmental factors permit, this characteristic y east community will result in a specific association contributing positivel y or negatively to the final product. The association that develops between yeasts and bacteria is governed by sp ecific key properties selecting for a few predominant yeasts. These yeasts may either stimulate or inhibit normal bacterial growth. The extent to whic h interaction between yeasts and bacteria contribute to the final product i s discussed. (C) 2001 Elsevier Science B.V. All rights reserved.