Control of food spoiling bacteria in cooked meat products with nisin, lacticin 3147, and a lacticin 3147-producing starter culture

Nisin, in the form of the commercial product Nisaplin, and lacticin3147 in whey powdered form were added to minced pork-meat in amounts of 0.15%(w/w) and 1.5%(w/w), respectively. The meat was cooked and inoculated with a Staphylococcusaureus strain of meat origin and a Listeriainnocua strain at a level of 10⁷ or 10⁵CFU g^-1. The batches were stored vacuum-packaged for 21days at 8°C. Nisin and lacticin3147 immediately reduced the L. innocua population at the time of inoculation. Nisin showed higher inhibitory activity than lacticin3147. During the storage period, a slight L. innocua growth was observed in the batches inoculated with the larger inoculum, and a bacteriostatic effect was observed against Listeria in the batches inoculated with 10⁵CFUg^-1. Nisin maintained a constant S.aureus population in the cooked batch inoculated with 10 ⁷CFUg^-1, although the bacteriocin was capable of reducing the amount of S.aureus by 90% in the batch inoculated with 10⁵ CFUg^-1. On the other hand, lacticin3147 did not show an inhibitory effect against S.aureus in the cooked meat. The starter culture Lactococcuslactis DPC303-T4 (containing the conjugative plasmid encoding production of lacticin3147) was inoculated in a portion of a Longissimusdorsi pork muscle with brine. L.lactis DPC 303-T4 performed a good fermentation, but lacticin 3147 production was not found after 7 days at 12°C of storage.