Growth Response of Putrefactive Anaerobe 3679 to Combinations of Potassium Sorbate and Some Common Curing Ingredients (Sucrose, Salt, and Nitrite), and to Noninhibitory Levels of Sorbic Acid

Abstract

ABSTRACT The effects of some common curing ingredients (sucrose, sodium chloride, and nitrite) on sorbate-induced inhibition were tested in putrefactive anaerobe (PA) 3679, a proteolytic species of Clostridium. A noninhibitory concentration (1%) of sucrose was not synergistic with the inhibitory action of potassium sorbate (30 mM; pH 6). The effect of sodium chloride depended upon the concentration used; a combination of 3% NaCl and sorbate (30 mM; pH 6) was more inhibitory than either compound alone but 1% NaCl reduced the inhibitory action of sorbate (30 mM; pH 6). Combining a noninhibitory concentration of nitrite (100 pM) and sorbate (30 mM; pH 6) was bactericidal to PA 3679. Nitrite raised the intracellular pH (pHi) and increased the protonmotive force (PMF) of untreated and sorbate-treated cells. Growth of PA 3679 was stimulated by the addition of a noninhibitory level of undissociated sorbic acid (5.5 mM; pH 7) or 0.1% glucose (5.5 mM) to a nutrient-deficient medium (0.25% trypticase [BBL]) but growth initiated more rapidly when sorbic acid was added than when the medium was supplemented with glucose. Results of this study are discussed in relation to the possible mechanisms of preservative action and suggest that certain recent changes in methods of food processing and packaging may increase the possibility of growth of clostridial organisms, including Clostridium botulinum.