Acid and Acidified Food Microbiology

Since C. botulinum spores cannot germinate and grow in foods at pH values below approximately 4.8 (regulations setting pH 4.6 as the cutoff between low-acid and acid/ acidified include a safety factor), heat treatments for acid and acidified foods need not destroy the spores of this organism. Heat treatments for products with pH values <4.0 are designed to inactivate yeast, molds, and lactic acid bacteria that can cause spoilage. The most resistant of these organisms have D15(rF values on the order of 1.0 min. A notable exception are the ascospores of the heat-resistant molds such as Byssochlamys, Neosartorya, and Talaro-myces (6-8). These organisms may have D194oF values of 1 to 12 min, which allow them to survive commercial processes; fortunately, such spoilage is rare.

For products with pH values between 4.0 and 4.6, there are spore-forming bacteria that can be important in spoilage. Of greatest importance are Bacillus coagulans and the butyric anaerobes such as Clostridium pasteurianum and C. butyricum. Products in this pH range are usually given more severe heat treatments to prevent spoilage from these organisms. Recently, spoilage in fruit juices has been caused by spore formers of the newly recognized genus Ali-cyclobacillus (9). These organisms can grow and spoil products at pH 3.5, and they can survive the commercial processes for juice products. Studies to characterize and control these organisms are under way; as with heat-resistant molds, spoilage of this type is not common.

Although the ability of pathogens such as Salmonella and E. coli 0157:H7 to grow in acid and acidified foods depends on the food, the pH, the acidulent, and other factors, it is not always necessary for these pathogens to grow to make someone sick. Thus it is important that these organisms be destroyed by a heat treatment. The pasteurization treatments given acid and acidified foods are more than adequate to kill these pathogens, as well as organisms such as the enteric protozoan parasite Cryptosporidium. In recent years, all three of these pathogens have caused outbreaks of foodborne illness as the result of consumption of contaminated, unpasteurized fruit juices (10).

The Mammoth Book of Bath and Beauty Recipes

The Mammoth Book of Bath and Beauty Recipes

This electronic book has all you will ever need for making homemade bath and beauty products in one place.

Get My Free Ebook


Post a comment