Evaluation of the efficacy of four weak acids as antifungal preservatives in low-acid intermediate moisture model food systems

• Published in: Food microbiology 2010-02, Vol.27 (1), p.33-36
• Main Authors: Huang, Yang, Wilson, Mark, Chapman, Belinda, Hocking, Ailsa D.
• Format: Article
• Language: English
• Subjects: Acids - pharmacology; Antifungal Agents - pharmacology; antifungal properties; Aspergillus flavus; Aspergillus niger; culture media; dehydroacetic acid; dissociation; Eurotium; Eurotium herbariorum; Eurotium rubrum; food contamination; food industry; food preservation; food preservatives; Food Preservatives - pharmacology; food spoilage; Food spoilage fungi; Fungi - drug effects; Minimal inhibitory concentration; minimum inhibitory concentration; model food systems; Models, Biological; molds (fungi); octanoic acid; Penicillium roqueforti; Penicillium roquefortii; potassium sorbate; salt concentration; salts; sorbic acid; Undissociated form; water activity; water content; Weak acid
• ISSN: 0740-0020; 1095-9998
• DOI: 10.1016/j.fm.2009.07.017

The potential efficacy of four weak acids as preservatives in low-acid intermediate moisture foods was assessed using a glycerol based agar medium. The minimum inhibitory concentrations (MIC, % wt./wt.) of each acid was determined at two pH values (pH 5.0, pH 6.0) and two a w values (0.85, 0.90) for five food spoilage fungi, Eurotium herbariorum, Eurotium rubrum, Aspergillus niger, Aspergillus flavus and Penicillium roqueforti. Sorbic acid, a preservative commonly used to control fungal growth in low-acid intermediate moisture foods, was included as a reference. The MIC values of the four acids were lower at pH 5.0 than pH 6.0 at equivalent a w values, and lower at 0.85 a w than 0.90 a w at equivalent pH values. By comparison with the MIC values of sorbic acid, those of caprylic acid and dehydroacetic acid were generally lower, whereas those for caproic acid were generally higher. No general observation could be made in the case of capric acid. The antifungal activities of all five weak acids appeared related not only to the undissociated form, but also the dissociated form, of each acid.