Antibacterial activity of water activity, lemon essential oil and leuconostoc mesenteroides on escherichia coli growth in tomato puree at 4 and 30°c

Abstract

In a previous work we demonstrated that Leuconostoc mesenteroides ssp. mesenteroides Tsc inhibited the development of the autochthonous microflora on tomato purée. We investigated the antibacterial effect of reduced water activity (0.97), lemon essential oil (150 ppm), L. mesenteroides Tsc and its metabolites, D-lactic (3.5 g/l) and acetic (3.0 g/l) acids, on E. coli ATCC 25922 growth in tomato purée at 4 and 30°C. At 30oC E. coli ATCC 25922 grew about 2 log cycles for 24 h, thereafter followed by complete elimination at day 10. At refrigeration temperature, it did not develop but survived during storage. In culture performed with the Tsc strain or D-lactic and acetic acids the initial population of E. coli began to decrease rapidly, no viable cells being detected at 3-4 days at 30oC. In this condition the reduced aw also showed a significant inhibitory effect. At 4oC, the Tsc strain or its metabolites showed the highest inactivation rates, although to a lower extent than at the higher temperature. In both tested conditions lemon essential oil caused the lowest inactivation rate. In conclusion, the Tsc strain and its metabolites would be more efficient for potential application for the preservation of minimally processed vegetable products.