Antimicrobial Effect of Natural Food Preservatives in Fresh Basil-Based Pesto Spreads

Abstract

Potential hurdle effect of biopreservatives - bacteriocin nisin and sugar alcohol xylitol (at pH=5.2 and 4.8) - on indigenous flora and water activity (Aw) of fresh basil-based pesto spreads was studied as alternative to traditional pasteurization or acidification treatments. Addition of 4% xylitol in pesto spreads (at pH5.2) resulted in a 0.8-log decrease in the total number of bacteria, after 14 days of storage at 4C, and depression of Aw from 0.886 to 0.864. Nisin (0.015%, at pH4.8) decreased the bacterial growth by 1 log after 14 days, at 4C. The antimicrobial activity of nisin and xylitol was evaluated against several microorganisms isolated during the preparation of pesto spreads: Staphylococcus aureus, Pseudomonas aeruginosa and Bacillus sp., and on laboratory cultures of Listeria innocua and Lactobacillus sp. An additive effect of 0.005% nisin and 5% xylitol on growth inhibition of pure culture of S.aureus was found. Practical Applications Application of natural antimicrobial substances may extend the microbiological life by minimizing food safety problems associated with uncooked processed products. Findings obtained in this study suggest a potential future application of bacteriocin nisin combined with additional hurdles: short temperature treatments of components, pH4.8 and intermediate NaCl concentration in preservation of food.