Assessment of the antifungal activity of Lactobacillus and Pediococcus spp. for use as bioprotective cultures in dairy products.

Fungi are commonly involved in dairy product spoilage and the use of bioprotective cultures can be a complementary approach to reduce food waste and economic losses. In this study, the antifungal activity of 89 Lactobacillus and 23 Pediococcus spp. isolates against three spoilage species, e.g., Yarrowia lipolytica, Rhodotorula mucilaginosa and Penicillium brevicompactum, was first evaluated in milk agar. None of the tested pediococci showed antifungal activity while 3, 23 and 43 lactobacilli isolates showed strong antifungal activity or total inhibition against Y. lipolytica, R. mucilaginosa and P. brevicompactum, respectively. Then, the three most promising strains, Lactobacillus paracasei SYR90, Lactobacillus plantarum OVI 9 and Lactobacillus rhamnosus BIOIII 28 at initial concentrations of 105 and 107 CFU/ml were tested as bioprotective cultures against the same fungal targets in a yogurt model during a 5-week storage period at 10 °C. While limited effects were observed at 105 CFU/ml inoculum level, L. paracasei SYR90 and L. rhamnosus BIOIII 28 at 107 CFU/ml respectively retarded the growth of R. mucilaginosa and P. brevicompactum as compared to a control without selected cultures. In contrast, growth of Y. lipolytica was only slightly affected. In conclusion, these selected strains may be good candidates for bioprotection of fermented dairy products.