Purpose: The objectives of this study were to determine the efficacy of individual treatments of acidified calcium sulfate with lactic acid (ACSL; 25%), ε-polylysine (EPL; 10%), hydrogen peroxide (HP; 5%), lauric arginate (LAE; 2%, 5%), and sodium caprylate (SC; 10%) applied as aqueous dip solutions to control Lm on fresh cheese; and, to identify antimicrobial interactions of combinatory treatments of LAE+EPL, EPL+SC, ACSL+SC, and LAE+SC.
Methods: Samples of Queso Fresco (25 g), from three independent batches of cheese, were surface inoculated with an Lm cocktail to achieve ca. four log CFU/g. The cheese was submerged in antimicrobial solutions for 60 s, vacuum-packaged, and then stored at 7°C for 35 days. Counts of Lm were determined after 24 h and then weekly throughout storage.
Results: Overall, HP was the most effective bactericidal and bacteriostatic treatment, reducing counts to <one log CFU/g within 24 h and through 35 days. Treatment with SC was the only other single treatment with Lm counts significantly lower than the control count on day 35 (P<0.0001). The combination treatment of EPL+LAE initially produced a two log CFU/g inactivation, but over time there was no difference in Lm counts. In contrast, counts from the combination treatments of ACS+SC, EPL+SC, and LAE+SC were significantly lower than the control throughout storage and when each of the compounds was applied individually at day 35 (P<0.05). Though these combinations were effective, the only synergistic treatment identified was ACSL+SC.
Significance: These data indicate that HP and several combinatory dip treatments, notably ACSL+SC, are promising approaches for controlling Lm on fresh cheese throughout a 35-day shelf-life.