TEA EXTRACTS AS POSSIBLE NATURAL FOOD PRESERVATIVE FOR ORGANIC FOOD

Abstract

The inhibitory effect of hot water extracts of green and black tea on some food spoilage and poisoning microorganisms was assayed using the in vitro zone inhibition technique. The antimicrobial effect of tea extracts was evaluated on various representatives of different microbial groups i.e. filamentous fungi (Aspergillus niger, Aspergillus oryzae, Fusarium moniliforme, Trichoderma viride & Trichoderma reesei), yeasts (Candida lipolytica, Candida utilis, Geotricum candidum & Saccharomyces cerevisiae), gram positive bacteria (Bacillus cereus & Staphylococcus aureus) and gram negative bacteria (Erwinia carotovora and Escherichia coli). Generally, extracts of the black tea showed stronger antifungal action on the different tested fungi than that of the green tea. Also, the highest concentrations of both tested tea extracts gave the strongest antifungal action. However, Staphylococcus aureus was the only gram positive bacteria which were inhibited by the higher tested concentrations of black tea, while green tea gave no inhibition effect. Whereas, the different tested concentrations of black tea inhibited the tested gram negative bacteria i.e. Erwinia carotovora and E. coli while green tea extracts at 3 and 4 % concentration inhibited only E. coli. Also, C. lipolytica was the only tested yeast which expressed growth inhibition at the different tested concentrations of both green and black tea extracts. It could be concluded that tea extracts could be used as natural food preservative in the processed organic food and/or beverage, which might be subjected to fungal spoilage.