Anti-listerial activity of chitosan and Enterocin 416K1 in artificially contaminated RTE products

We investigated the anti-listerial activity of chitosan and Enterocin 416K1 alone or in association by three different experiments performed (i) in agar well diffusion, (ii) in buffer suspensions assay, (iii) in RTE vegetables and fruit artificially contaminated with Listeria monocytogenes NCTC 10888. All tests demonstrated the anti-listerial activity of the natural bioactives and the best action obtained by their use in combination. In the artificially contaminated vegetables (trial 1 zucchini, corn, radishes; trial 2 mixed salad, carrots, zucchini) the inhibition of listeria was almost comparable, with the greatest killing activity observed in samples added with both antibacterial substances. In the artificially contaminated fruits (trial 3 apples, grapes; trial 4 pineapple, melon) a more evident anti-listerial activity in samples treated with chitosan enterocin in association also emerged. In particular, in trial 3 we obtained a total killing of listeria within 72 h, while in trial 4 there was only a minimal inhibition, difference attributable to the composition of the two samples. Considering the results obtained, we can conclude that the use of chitosan and Enterocin 416K1, alone or in combination, could be a feasible solution to extend the shelf life and to obtain the microbiological safety of ready-to-eat vegetable and fruits. (C) 2011 Elsevier Ltd. All rights reserved.