Inhibitory Effect of Unripe Grape Products on Foodborne Pathogens

Abstract

Low quality unripe grapes can be processed into various products such as verjuice and sour grape sauce. In this study, the minimum inhibitory concentrations (MICs) of five verjuice and five sour grape sauce samples on Bacillus cereus, Escherichia coli, Listeria monocytogenes, S. Typhimurium, and Staphylococcus aureus were determined. The microbiological quality of the samples and the presence of the test cultures in them were determined before analysis. The pH, titratable acidity (%), and the MIC values of the samples ranged from 2.14 to 2.74, 2.29–7.09%, and, 1:2(50%)−1:16(6.25%), respectively. The MIC values of the neutralized unripe grape products (UGPs) were determined, and it was detected that the inhibitory effects of UGPs mainly depends on the acidity. The inhibitory effect is related to the concentration and it decreases through dilution. It was concluded that UGPs could be considered as good alternatives for functional and safe foods with their antimicrobial properties. Practical Applications In recent years, consumer demands have increased regarding safety and natural foods. Food producers have been avoiding the use of chemical preservatives, and tend to use nonthermally processed foods. Thus, researchers have been studying on examining natural antimicrobial agents to ensure food safety. The natural antimicrobial agents may be obtained from animals, microorganisms, and plants. The effects of plant based antimicrobials are based on the composition of organic acid and phenolic compounds in the materials. The minimum inhibitory concentrations of unripe grape products while they were neutralized and un-neutralized were investigated to evaluate their potential as natural antimicrobials in this study. While the unripe grape products are widely used as acidifying and flavoring agents in foods and beverages, they are also considered as natural antimicrobial agents on foodborne pathogens.