Developing, validating processes for fermented foods.

We know that fermentation increases the vitamin and enzyme content of foods, aids digestion and facilitates the assimilation of nutrients. Fermented foods also colonize the intestinal tract with flora that control putrefactive bacteria, maintain proper pH balance in the colon, and increase the bulk and frequency of bowel movements.

Acidified and fermented foods have enjoyed excellent safety records, with few or no cases of foodborne disease reported from the consumption of these products. However, there have been reports of disease outbreaks caused by E. coli O157:H7 and Salmonella species in juice products that have pH values of less than 4.0. These outbreaks may raise concerns about the safety of some acidified products.

Acidified foods contain acid or acid food ingredients and must have a water activity of 0.85 or greater and a final equilibrium pH of 4.6 or less. These regulations were promulgated by the FDA in 1979, with the intent of preventing spore germination and any growth of C. botulinum. At that time, vegetative cells of bacteria were not considered to be a significant health risk for acidified or fermented food products. Acid foods, including fermented products, and refrigerated foods are exempt from these regulations. In 2001, the FDA began holding commercial process filings for acidified foods that were not heat-processed. Exceptions included products with an equilibrium pH value at or less than 3.3 that are acidified with acetic acid. For theses products, only a holding time of 48 hours is needed before their distribution to ensure safety.

For acidified foods with a pH greater than 3.3, the minimum heat treatments needed for a 5-log reduction in the number of pathogenic bacteria are the objective of current research efforts. Research is underway in several laboratories to determine how organic acids present in fermented and acidified vegetable products can be used to destroy acid-resistant food pathogens. Scientists also are determining the molecular mechanisms by which these pathogens resist killing by acid. Results from this research may lead to specific recommendations for the safe production of acidified and fermented food products.

Further information. Fred Breidt, Department of Food Science, North Carolina State University, 322 Schaub Hall, Box 7624, Raleigh, NC 27695; phone: [phone]; fax: [phone]; email: [e-mail].