Bacterial spore resistance to acid

Abstract

Available data on the effects of acidic pH on bacterial spores (Bacillus and Clostridium genera) and the possible mode of inhibition of bacterial growth are reviewed and discussed relative to food safety or food quality defects. Many factors affect the conversion of spores to cells (activation, germination, outgrowth leading to increased turbidity) and the growth and survival of spore-forming bacteria. Other factors affect spore resistance: the type of acid present, water activity on minimum pH necessary for growth, the oxidation-reduction potential of the medium, and the type and level of reducing agent present. Antimicrobial treatments (heat, nitrite, EDTA, phenolics, trace fatty acid levels, nisin, sanitizers) enhance growth inhibition at reduced pH. Data concerning Clostridium botulinum growth below pH 4.6 are discussed. Extensive tabular data are presented from bacterial growth inhibition studies. (wz)