Potential Use of Lactic Acid Bacteria with Pathogen Inhibitory Capacity as a Biopreservative Agent for Chorizo

The biopreservation of meat products is of great interest due to the demand for products with low or minimal chemical additives. Lactic acid bacteria (LAB) have been used as protective cultures for many centuries. The objective of this work was to characterize 10 native LAB isolated from meat masses with biopreservative potential for meat products. The isolates were subjected to viability tests with different concentrations of NaCl, nitrite, and nitrate salts, pHs, and temperature conditions. Antibiotic resistance and type of lactic acid isomer were tested. In addition, the isolates were tested against seven pathogens, and inhibitory substances were identified by diffusion in agar wells. Finally, two isolates, Lb. plantarum (SB17) and Lb. sakei (SB3) were tested as protective cultures of chorizo in a model. As a result, the viability at different concentrations of NaCl and nitrate and nitrate salts were obtained. pH and temperature exerted a negative effect on the growth of some of the isolates. Pathogens were inhibited mainly by the presence of organic acids; P. aurius was the most susceptible, and S. typhimurium and S. marcescens were the most resistant. The strains SB17 and SB3 had similar effects on chorizo, and time exerted a deleterious effect on microbiological quality and pH. The results indicated that the 10 isolates show promising characteristics for the preservation of cooked meat products, with the strain Lb. plantarum (SB17) being the most promising.

Effect of commercial protective cultures and bacterial fermentates on Listeria monocytogenes growth in a refrigerated high-moisture model cheese

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.