The ecological diversity of yeasts in dairy products
1998
Viljoen, B.C. (University of the Orange Free State, Bloemfontein (South Africa). Dept. of Food Science)
The field of yeast ecology concerns the manner in which yeasts and yeast-like organisms survive and progenerate in nature, and where the specific organisms can be found. The modern concept of yeast ecology includes every food item as a potential habitat of yeasts because of the availability of the necessary nutrients for growth. Since dairy products have a characteristic nutritional composition, a specific association of yeasts is expected. The origin, development, and succession of this association are not only determined by the composition of nutrients available, but are also governed by environmental ecological factors that influence the physiological expression of the genetic constitution of the yeast cells. Due to the general environment from which the dairy product was originally obtained and the microbiological quality of the product in its raw or processed state, it is inevitable that dairy products become contaminated by yeasts from different sources in the environment. Only a part of the primary microflora will survive under the selective pressures exerted by the intrinsic and extrinsic biotic factors present, processing procedures and preservatives. The yeasts also lend inherently to adapt to certain environmental circumstances. Yeasts that possess the proper physiological attributes to counteract the specific ecological determinants will be favoured. Eventually, a particular yeast community will result in a specific spoilage association determined by the ecological factors in a given product. In this paper I have endeavoured to identify the ecological determinants and the effects thereof on foodborne yeasts.
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