Evaluation of frankfurters formulated with potassium lactate and sodium diacetate and innocualted with Listeria monocytogenes before and after irradiation treatment

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.