Objective: To establish the principles for determination and evaluation of the preservative properties demonstrates the effectiveness of a substance when used as a food preservative.
Methods: Sorbic acids were chosen as the model food preservative and the Gram positive bacterium Staphylococcus aureus, Gram negative bacteria Escherichia coli and Salmonella enteritidis, yeast Candida albicans and the filamentous fungus Aspergillus niger, A. flavas, Geotrichum candidum, Penicillium islandicum and Peniciuium cyclopium were employed as the experimental microorganisms. The test involves adding fresh and active cultures standardized to a concentration between 10(2) and 10(5) cfu/ml directly to sorbic acid solution at different concentrations ranged from 0.25 to 2 g/L to simulate contamination. The mixture was held for two days and microorganism survivals were monitored at regular intervals of 3, 6, 24 and 48 h, respectively.
Results: Sorbic acids were active against an extensive range of bacteria, yeasts and molds. The inhibition got stronger and stronger with either the extension of time against microorganisms or the increasing in concentration of sorbic acid. The antibacterial activity of sorbic acid were a little bit stronger than its antimycotic activity, with the lower minimum inhibitory concentration and the shorter inhibitory time in bacteria than those in fungi. In general, Gram negative bacteria were more sensitive to sorbic acid than Gram positive one.
Conclusion: The experimental design could be science-based, sound and available in evaluation of the antimicrobial effectiveness of food preservatives.