Control of Listeria spp. and Salmonella spp. in Regular and Ultrafiltered Raw Milk Cheddar Cheese Curds Stored at Room and Refrigeration Temperature

Abstract

Cross contamination of ready-to-eat food is a substantial concern in spreading pathogenic organisms, such as Salmonella spp. and Listeria monocytogenes. During the production of cheddar cheese curds, the lactose sugar molecules naturally present in the milk are converted to lactic acid via the good bacteria inoculated into the milk. Lactic acid bacteria can produce antimicrobial molecules known as bacteriocins. Milk also naturally contains the anti-microbial protein lactoferrin. Listeria spp. and Salmonella spp. were inoculated onto the surface of different cheese varieties and stored at either room or refrigeration temperature. Regarding Listeria spp. contamination, cheese curds and raw ultrafiltered milk cheese curds stored at room temperature showed the most considerable statistically significant log reductions of 1.2 and 3.4, respectively. In terms of Salmonella spp. contamination, these treatments also showed the most considerable statistically significant log reductions of 3.3 and 4.7, respectively. In addition, raw regular milk cheese curds also showed a significant log reduction for Salmonella spp. of 4.7. Overall, cheeses stored at room temperature exhibited the most significant log reductions. Cheeses manufactured with ultrafiltered milk tended to reduce pathogens significantly more than cheeses made with regular milk. Ultrafiltration technology could reduce the number of recalls seen on cheese, giving consumers a sense of ease while at the grocery store and providing the dairy industry with an overall economic benefit. Further research is needed to confirm if the lactoferrin levels are higher in ultrafiltered milk than regular milk.