Chitosan potentiates the antimicrobial action of sodium benzoate on spoilage yeasts.

The objective of this study was to determine whether low concentrations of chitosan and benzoate in combination could be used to enhance the antimicrobial action of either compound alone against three spoilage yeasts in saline solutions. Saccharomyces exiguus, Saccharomycodes ludwigii and Torulaspora delbrueckii were suspended in 0.05 and 0.005% chitosan glutamate and 0.025% sodium benzoate, alone or in combination, in 0.9% saline solutions at pH 6.2 and 4.5. Survivor curves were constructed from viable counts determined periodically for up to 120 min. Chitosan at 0.005% almost doubled the extent of death caused by 0.025% benzoate alone, from about 1-2 log to about 2-4 log cfu ml(-1), depending on pH and target organism. Chitosan (0.005%) and 0.025% sodium benzoate acted synergistically against spoilage yeasts in saline solutions. These results suggest that the natural compound chitosan may be useful as an adjunct in the potentiation of the biocidal efficacy of antimicrobial compounds such as benzoates.