I I Ground pork shoulders were combined with SO/SO pork trimmings to achieve fat levels of 20.0, 23.3, 26.6, and 30.0%. Salt/phosphate (NaCl/POq) combinations of O/O, l/O, l/O.25 and 2%/0.5% were blended with each fat level. Each treatment combination was stored at 3°C for 7 days in air-permeable film (AP), 21 days in vacuum pouches (VP) and at -23°C for 90 days in double-wrapped (DW) freezer paper. Fat level did not affect pH, expressed moisture (EM), peroxide value (PV), 2-thiobarbituric acid (TBA) values or cooking losses. Patties with 30.0% fat were jucier and required less energy to compress. A combination of 1% NaCl/0.25% PO4 reduced cooking losses, enhanced sensory properties and moderated the oxidation effects of NaCl up to 60 days of frozen storage. The NaCl treatment accelerated lipid oxidation most during all storage conditions while the control remained the least oxidized.

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Combining food antimicrobials can enhance inhibition of Listeria monocytogenes in ready-to-eat (RTE) meats. A broth dilution assay was used to compare the inhibition of L. monocytogenes resulting from exposure to nisin, acidic calcium sulfate, ε-poly-L-lysine, and lauric arginate ester applied singly and in combination. Minimum inhibitory concentrations (MICs) were the lowest concentrations of single antimicrobials producing inhibition following 24 h incubation at 35 °C. Minimum bactericidal concentrations (MBCs) were the lowest concentrations that decreased populations by ≥3.0 log(10) CFU/mL. Combinations of nisin with acidic calcium sulfate, nisin with lauric arginate ester, and ɛ-poly-L-lysine with acidic calcium sulfate were prepared using a checkerboard assay to determine optimal inhibitory combinations (OICs). Fractional inhibitory concentrations (FICs) were calculated from OICs and were used to create FIC indices (FIC(I)s) and isobolograms to classify combinations as synergistic (FIC(I) < 1.00), additive/indifferent (FIC(I)= 1.00), or antagonistic (FIC(I) > 1.00). MIC values for nisin ranged from 3.13 to 6.25 μg/g with MBC values at 6.25 μg/g for all strains except for Natl. Animal Disease Center (NADC) 2045. MIC values for ε-poly-L-lysine ranged from 6.25 to 12.50 μg/g with MBCs from 12.50 to 25.00 μg/g. Lauric arginate ester at 12.50 μg/g was the MIC and MBC for all strains; 12.50 mL/L was the MIC and MBC for acidic calcium sulfate. Combining nisin with acidic calcium sulfate synergistically inhibited L. monocytogenes; nisin with lauric arginate ester produced additive-type inhibition, while ε-poly-L-lysine with acidic calcium sulfate produced antagonistic-type inhibition. Applying nisin along with acidic calcium sulfate should be further investigated for efficacy on RTE meat surfaces.

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