Evaluation of frankfurters formulated with potassium lactate and sodium diacetate and innocualted with Listeria monocytogenes before and after irradiation treatment
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Abstract
Microbial safety and quality attributes were evaluated for frankfurters formulated with potassium lactate/sodium diacetate (0 or 3%) and inoculated with a four-strain Listeria monocytogenes cocktail before and after treatment with pasteurizing doses of irradiation (0, 1.8, or 2.6 kGy). Frankfurters were inoculated after irradiation and stored aerobically for 4 wk at 4 ??C to simulate the product becoming contaminated after opening, or they were inoculated prior to vacuum packaging and stored for 8 wk at 4 ??C. Incorporation of lactate/diacetate into frankfurter formulations with or without irradiation had a strong listeriostatic effect throughout 4 wk of aerobic storage. Total microbial counts for frankfurters formulated with lactate/diacetate remained constant throughout storage while those without increased steadily (5.4 to 9.3 log cfu). Over 4 wk of storage, the outgrowth of L. monocytogenes on frankfurters formulated with lactate/diacetate was effectively suppressed and counts were not significantly different from initial counts (5.2 vs. 5.0 log cfu, respectively). Irradiation treatments alone had significantly higher L. monocytogenes counts after 3 wk of storage. Both treatments together or alone were not detrimental to sensory aroma or flavor attributes. Meaty/brothy complex, smoke, spice aroma, springiness, and cohesiveness attributes were judged slightly lower for frankfurters formulated without lactate/diacetate than those with lactate/diacetate at the end of aerobic storage. Sensory color was not dramatically influenced by either treatment, however, Lab* values of all treatments decreased slightly during storage. Both the addition of lactate/diacetate to a frankfurter formulation and irradiation were effective towards controlling microbial growth of L. monocytogenes in an unopened vacuum package after 8 wk of storage. Large and incremental reductions in total microbial counts were seen with irradiation treatment, which were maintained throughout storage with lactate/diacetate treated frankfurters. There were fewer influences on sensory characteristics for vacuum packaged frankfurters compared to those aerobically packaged. Overall, lactate/diacetate addition and irradiation to a lesser extent were effective towards retarding the outgrowth L. monocytogenes on frankfurters while maintaining quality attributes throughout aerobic storage. The combination of irradiation and lactate/diacetate were effective for reducing and retarding growth of L. monocytogenes and especially during the last two weeks of vacuum packaged storage.