Efficacy of Reuterin and Bacteriocins Nisin and Pediocin on Preservation of Raw Milk Procured from Dairy Farms

Abstract

Research background. In the current scenario of milk production in developing and developed countries, several factors influence the shelf-life of raw milk and add significant numbers of microbial contaminants that drastically lower the initial microbial quality leading to milk spoilage by the time it reaches the processing points. Experimental approach. The present study was undertaken to study the bio-preservative efficacy of reuterin system along with different combination of bacteriocins to control the initial microflora of raw milk at farm level. Lactobacillus reuteri strain LR47, having effective antimicrobial activity was shortlisted from our previous study and further characterized for reuterin production and tested in raw milk system. Results and conclusions. Preliminary testing of the cell-free supernatant from L. reuteri LR47 significantly demonstrated inhibition of growth of the majority of the tested bacterial indicators. Further genetic analysis of the L. reuteri LR47 revealed the presence of two genes (pduC and dhaB) involved in the utilization of glycerol to produce reuterin using two different pathways. The strain LR47 was also found to possess comparatively higher capacity to convert glycerol into reuterin when checked through colorimetric assay. In the raw milk bio-preservation experiment with reuterin alone or in combination with bacteriocins, the highest level of growth suppression in the total bacterial load and coliform counts was observed in the sample that was treated with a triple combination of reuterin, nisin, and pediocin. The treatment combining these 3 natural bio-preservatives at specific concentrations was able to maintain the initial microbial quality and extend the shelf-life of raw milk by 6 h at 37 °C based on the microbial counts and physicochemical properties viz. pH and titratable acidity. In conclusion, the results confirm that the use of reuterin combinations with bacteriocins is a promising approach for temporarily controlling the raw milk microflora and extend its shelf-life until further processing. Novelty and scientific contribution. This study demonstrates for the first time the use of reuterin for the extension of shelf-life of raw milk as an alternative treatment method.