Evaluation of the antifungal effect of metabolites of bioprotective cultures: dairy food applications

Abstract

To guarantee the food safety and shelf life of many processed food products, the food industry has made use of artificial preservatives that are each time more questioned and replaced by natural alternatives such as bioprotective cultures. Lactic acid bacteria (LAB) and propionic acid bacteria (PAB) are bacterial groups recognized by their antimicrobial action against bacterial pathogens but their activity against fungi is lesser known. The present study evaluated the antifungal functionality of three strains Lactobacillus casei, three of L. rhamnosus, and three of Propionibacterium freudenreichii against isolates of Mucor circinelloides and Geotrichum candidum and the effect of factors like pasteurization (74°C, 3 min) and culture media (milk and BRFS) on it. The challenge assays in dairy models (yogurt agar) produced the following results in accordance to a qualitative score scale of fungal growth: (1) different strains of LAB and PAB differed in the bioprotective functionality, (2) the heat treatment eliminated or reduced substantially the antifungal power with the exception of P. freudenreichii subsp. shermanii BPL0082, and (3) the cultures developed in media BRFS exhibited greater inhibition capacity.