Journal of Microbial & Biochemical Technology

Are natural antimicrobial phenolic compounds still efficient to limit Listeria monocytogenes growth in model food systems rich in poly-unsaturated fatty acids?

Joint Event on 4^th World Congress and Expo on Applied Microbiology & 2^nd International Conference on Food Microbiology

November 29-December 01, 2017 Madrid, Spain

Aurelia Pernin, Veronique Bosc, Stephanie Roux, Marie-Noelle Maillard and Florence Dubois-Brissonnet

UMR Micalis, INRA, AgroParisTech, France
UMR Ingéniérie Procédés Aliments, INRA, AgroParisTech, France

Posters & Accepted Abstracts: J Microb Biochem Technol

Abstract:

Over the last decade, in order to respect nutritional recommendations, food companies have modified the fatty acids�?? profile in their products. The proportion of polyunsaturated fatty acids (PUFA), mainly omega-3, is higher and as consequences, lipid oxidation and growth of some pathogenic microorganisms can be favored: bacteria could grow faster at low temperature due to the incorporation of exogenous PUFA that help to regulate their membrane fluidity. One solution to limit these phenomena is the use of molecules having both antioxidant and antimicrobial properties. Phenolic compounds, present in plants or agro-industry by-products, exhibit a well-known antioxidant potential and to a lesser extent, have been reported as antimicrobials even if their mechanism of action is not fully understood yet. The aim of this study was to evaluate the ability of natural phenolic compounds to inhibit Listeria monocytogenes growth in a complex food system: oil-in-water emulsions, rich in PUFA. The first step was to evaluate the antimicrobial activity of a series of natural phenolic compounds against L. monocytogenes by determining their Minimum Inhibitory Concentration and Non-Inhibitory Concentration in a simple broth medium. Results bring evidence on antimicrobial structure-activity relationships of several phenolic compounds and allow to hypothesize mechanisms of action of phenolic acids. The most efficient compounds were then challenged in oil-in-water emulsions. Microbial growth in emulsions containing antimicrobials was followed by colony counting on agar. Results point out significant differences compared to the simple broth. The partition coefficient (log P) of the compounds appears to be a key factor to determine their antimicrobial activity. In broth, a phenolic compound having a higher logP would partition more into the bacterial membrane and act as a better antimicrobial. In an emulsion, on the contrary, the compound would partition more into the lipid droplets, thus appearing less active by being physically separated from bacteria located into the aqueous phase.