Inhibition of Listeria monocytogenes on Beef Tissue by Application of Organic Acids Immobilized in a Calcium Alginate Gel

Organic acids added to calcium alginate gels and immobilized on lean beef tissue inoculated with Listeria monocytogenes (Lm) reduced the population significantly more than did acid treatment alone. Lactic acid (1.7% v/v) immobilized in alginate reduced counts by 1.3 log₁₀ units vs 0.03 log unit decrease from the acid treatment alone. Acetic acid (2% v/v) reduced counts 1.5 and 0.25 log units, respectively. Over 7 days, Lm proliferated in samples without acid and/or alginate treatment. Differential counts on selective and non-selective agars indicated sublethal cellular injury occurred. Alginate coatings did not enhance acid inhibition on fat tissue. Immobilized agents may have potential for raw meat decontamination.