When I was asked to write on "Aspects of Shelf-life," I was uncertain how to proceed. The factors that limit shelf-life and means to extend shelf-life are at once complex and simple. So, I will begin and end this piece with the same advice: "To maximize shelf-life, pay close attention to the quality of the incoming milk and other ingredients, product formulation, the selection of starter culture, the sanitation program in your plant and maintain the appropriate low-storage temperature."
The second category of microbial problems are those brought about by post-pasteurization contaminants. Common defects associated with these microorganisms include slime formation, changes in color, production of gas, development of "unclean" or "yeasty" flavors, and the visible presence of mold on the surface of products. In addition, some spoilage microorganisms produce diacetyl reductase, an enzyme that converts the buttery-flavored diacetyl to a flavorless compound.