Heat Processing

Pasteurization of milk is a legal requirement in the United States for manufacture of fresh cultured products (CFR Title 21, part 133:1995). Heat treatments typically employed for selected fermented milk products are depicted in Table 1.

The most important impact of heat processing is microbiological. Due to heat treatment, most vegetative bacteria, yeast, molds, and pathogens are destroyed (>5 log cycle reduction is required). This has a strong impact on safety and quality of the resultant product. Surviving spores are unlikely to cause problems, because Bacillus and Clostridium endospores do not germinate at the pH of most fermented milks (i.e., pH < 4.5) (20). Heat-stable enzymes are reported to not pose a significant problem in semisolid fermented milk products (21), with the exception of products like sour cream that may be critical for lipo-lytic or proteolytic spoilage. With regard to starter culture, reduced competition between

Table 1 Typical Heat Treatments Employed for Fermented Milk Preparations

Product

Typical heat treatment(s)

Reference

Yogurt

90-95°C for 2-5 min

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