Abstrait

Antimicrobial and preservative effect of berries in food models

Massoud Attarianshandiz*

Five different berries including aronia, blackcurrant, blueberry, cranberry and raspberry were examined for their antibacterial property against four different food-borne pathogens: Staphylococcus aureus, Listeria monocytogenes, Escherichia coli and Salmonella Typhimurium. To implicit the experiment standard broth and broth supplemented with food minimizing the inhibitory effect of organic acids, all berry extracts were pH neutralized. To do the experiment berry extracts were added to bacterial cultures (∼5×106 CFU/ml inoculum) and growth was observed over a 24h period. After the duration the determination of Minimal Inhibitory Concentrations (MIC), Minimal Bactericidal Concentrations (MBC) and log CFU/ml reductions, were noted. In addition, the content of the bioactive compounds; total anthocyanins and total polyphenols of all the berries were determined. Aronia, blackcurrant and blueberry had the highest antimicrobial activity and concentrations of polyphenols and anthocyanins. S. aureus and L. monocytogenes were more sensitive to the berry extracts than E. coli and S. Typhimurium. Considering the effect of aronia, blackcurrant and blueberry extracts against S. aureus and L. monocytogenes the antibacterial property remained significant (a=0.05) even at neutral pH and in presence of food constituents. However, the antimicrobial effects were influenced by food constituents with a major reducing effect likely mediated by proteins. Finally, extracts of berries with high content of polyphenols and anthocyanin’s like aronia, blackcurrant and blueberry have a significant antimicrobial effect against some food-borne bacteria, even at neutral pH mimicking common food products. It should be noted that even though, food constituents significantly increased the inhibitory concentration of berries, still, berries kept their potential as natural preservatives against important pathogens in many types of foods.