Survival of Listeria monocytogenes Scott A on vacuum-packaged raw beef treated with polylactic acid, lactic acid, and nisin.
Low-molecular-weight polylactic acid (LMW-PLA) and lactic acid (LA) were used to inhibit growth of Listeria monocytogenes Scott A on vacuum-packaged beef. Nisin was also used simultaneously as an additional hurdle to the growth of this pathogen. Inoculated beef cubes were immersed in a solution of 2% LMW-PLA, 2% LA, 400 IU/ml of nisin, or combinations of each acid and nisin for 5 min and drip-dried for 15 min. The cubes were then vacuum-packaged and stored at 4 degrees C for up to 42 days. Surface pH values of beef cubes treated with 2% LMW-PLA, the combination of 400 IU/ml of nisin and 2% LMW-PLA (2% NPLA), or 400 IU/ml of nisin alone were significantly reduced from 5.59 to 5.18, 5.01, and 5.19, respectively, whereas those decontaminated with 2% LA or 400 IU/ml of nisin and 2% LA (2% NLA) were significantly decreased from 5.59 to 4.92 and 4.83, respectively, at day 0 (P < or = 0.05). The 2% LMW-PLA, 2% LA, 2% NPLA, 2% NLA, and 400 IU/ml of nisin showed immediate bactericidal effects on L. monocytogenes Scott A (1.22-, 1.56-, 1.57-, 1.94-, and 1.64-log10 reduction, respectively) compared with the initial number of 5.33 log10 CFU/cm2 of the untreated control at day 0 (P < or = 0.05). These treatments, combined with vacuum-packaging and refrigeration temperature, succeeded to inhibit growth of L. monocytogenes during storage up to 42 days. At the end of 42 days, the numbers of L. monocytogenes Scott A remaining viable on these samples were 1.21, 0.36, 2.21, 0.84, and 0.89 log10 CFU/cm2, respectively.
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Department of Food Science, University of Missouri-Columbia, 65211, USA.
Mustapha
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Clarke
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D000818:Animals; D002417:Cattle; D005516:Food Microbiology; D018857:Food Packaging / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000494:pharmacology*; D008089:Listeria monocytogenes / Q000187:drug effects / Q000302:isolation & purification*; D008460:Meat / Q000382:microbiology*; D008970:Molecular Weight; D009561:Nisin / Q000494:pharmacology*; D011091:Polyesters; D011108:Polymers / Q000494:pharmacology*; D014618:Vacuum
D011091:Polyesters; D011108:Polymers; D009561:Nisin; D019344:Lactic Acid; C033616:poly(lactide)