Biopreservatives are clean-label ingredients used to control pathogenic and spoilage microorganisms in ready-to-eat foods including cheese. The efficacies of six commercial biopreservatives in controlling L. monocytogenes growth at 4°C were tested in a high-moisture model cheese (pH 6.00, 56% moisture, 1.25% salt) made of cream, micellar casein, water, salt, lactose, lactic acid, and a single protective culture (PC-1, PC-2, or PC-3, 10 6 CFU/g target) or bacterial fermentate (CM-1 or CM-2 [cultured milk] or CSV-1 [cultured sugar-vinegar blend], 0.5% or 1.0% level). Cheeses were inoculated with 3-log CFU/g L. monocytogenes (5-strain cocktail), after which 25-g samples were vacuum-sealed and stored at 4°C for 8 weeks. L. monocytogenes populations from triplicate samples were enumerated weekly on Modified Oxford agar in duplicate trials. L. monocytogenes growth (≥1-log increase) was observed in approximately 1 week in control cheese and those formulated with 10 6 CFU/g PC-1 or PC-2. Growth was delayed to 2.5 weeks in model cheeses formulated with 10 6 CFU/g PC-3 or 0.5% CM-2 and to 3 weeks with 0.5% CM-1 or CSV-1. Growth was further delayed to 6.5-7.5 weeks in model cheeses formulated with 1.0% CM-1 or CM-2, while formulation with 1.0% CSV-1 inhibited L. monocytogenes growth for 8 weeks. In a second set of experiments, the combined effect of pH and 0.5% CSV-1 on L. monocytogenes inhibition was investigated. Incorporation of 0.5% CSV-1 delayed L. monocytogenes growth to 3, 6, and >10 weeks in cheeses of pH 6.00, 5.75, and 5.50, respectively, versus growth observed in 1, 1, and 3.5 weeks in control cheeses. These data suggest that certain fermentates have greater antilisterial activity than protective cultures in directly acidified cheeses with direct biopreservative incorporation and refrigerated storage. Further research is needed to optimize conditions to prevent listerial growth utilizing protective cultures in fresh, soft cheeses.
Effect of a Lactobacillus sakei and Staphylococcus xylosus protective culture on Listeria monocytogenes growth and quality traits of Italian fresh sausage (salsiccia) stored at abusive temperature
