Antifungal activity and mechanism of monocaprin against food spoilage fungi

Monocaprin is generally recognized as a safe food additive and widely used as a functional emulsifier in food industry. In this work, the preservative ability of monocaprin against three food spoilage fungi, Saccharomyces cerevisiae, Aspergillus niger and Penicillium citrinum was investigated to evaluate the potential use of monocaprin as a potent food preservative. The minimum inhibitory concentrations (MIC) of monocaprin against these fungi were 0.31, 0.63 and 0.63 mg/mL, and the minimum fungicidal concentrations were 1.25, 2.50 and 2.50 mg/mL, respectively. The MICs remained unchanged when the pH values were increased from 3 to 9. After being exposed to monocaprin at MIC, the growth of A. niger or P. citrinum was completely inhibited for one week, and S. cerevisiae began to degrade at 100 h. These results indicated that monocaprin may be a potential preservative independent of pH. The mechanism of action was then investigated by the measurement of damage of cell walls, permeability of cell membrane, release of cellular contents and morphological observation. Results indicated that monocaprin may kill S. cerevisiae by disrupting the cell wall and plasma membrane, resulting in the release of cellular contents. Monocaprin inhibited A. niger spore and P. citrinum by increasing the permeability of the cell membrane and release of cellular contents, but not involving cell structure alteration. (C) 2017 Published by Elsevier Ltd.