Application of Lactobacillus helveticus CNRZ 32 to Control the Microbial Contaminants in Cheese by Addition of Bacterial Extracts or by In Situ Production of Bioactive Metabolites

Microbial spoilage of cheese represents a major concern from both health and economic views. The addition of food preservatives is considered the most applied strategy to ensure food quality and to control microbial contamination. It well established that natural preservatives such as Nisin and Natamycin are of great effectiveness against a wide range of microbial concerns, but the lack of wide spectrum effect induces looking for more efficient alternatives. This research suggests alternative treatments to be evaluated side by side with both Nisin and Natamycin within real cheese models to control microbial contamination during the storage period. To evaluate this, two varieties of cheese were manufactured and inoculated with a set of pathogen and cheese spoiling microorganisms. Talaga cheese batches were separately treated with extract of MRS that previously fermented by Lactobacillus helveticus CNRZ 32, Nisin and Natamycin at Free State and Chitosan Nanoparticles-loaded state to become 6 treatments (T1 – T6) other than the control (C). The same treatments were applied to Karish cheese batches, in addition to inoculation of Lactobacillus helveticus CNRZ 32 1% (v/v) in the seventh batch. Upon microbiological analyses, results show that T2; the extract loaded on Chitosan Nanoparticles completely reduced the count of all pathogens and spoiling populations after two weeks of cold storage (2 – 6oC) in Talaga cheese. In the case of Karish cheese, the 7th batch treated with Lactobacillus helveticus CNRZ 32 inoculation had no pathogenic nor spoiler growth after one week of cold storage (2 – 6oC). These results suggest that Lactic acid bacteria especially Lactobacillus helveticus CNRZ 32 can efficiently ensure the safety and quality of cheese if applied in appropriate form.