The Pork Meat or the Environment of the Production Facility? The Effect of Individual Technological Steps on the Bacterial Contamination in Cooked Hams

Abstract

The aim of this study was to analyse the influence of the contamination level of fresh meat on the bacterial population in raw material before cooking and on the microbiota of cooked hams following heat treatment. The effect of incubation temperatures of 6.5 and 15 °C on the results obtained was also evaluated during the bacteriological investigation. The total viable count (TVC), the number of Enterobacteriaceae and lactic acid bacteria (LAB) were determined in the samples. LAB were isolated from 13 samples out of the 50 fresh meat samples. The species most frequently detected included Latilactobacillus sakei, Leuconostoc carnosum, Enterococcus gilvus, Latilactobacillus curvatus, and Leuconostoc gelidum. The meat sampled after the brine injection and tumbler massaging showed higher bacterial counts compared to fresh meat samples (p < 0.001). The heat treatment destroyed the majority of the bacteria, as the bacterial counts were beneath the limit of detection with a few exceptions. Although the primary cultivation of samples of cooked hams did not reveal the presence of LAB, their presence was confirmed in 11 out of 12 samples by a stability test. Bacteria of the genus Leuconostoc were the most numerous.

Characterization of Leuconostoc carnosum and Latilactobacillus sakei during Cooked Pork Ham Processing

“…Moreover, previous studies also reported rapid LAB growth from initially low LAB levels in freshly packed cooked ham [ 5 , 30 , 33 ]. The intrinsic characteristics of cooked ham, such as water activity, sugar-enriched preparations, and the presence of sodium chloride and sodium nitrite, provided a selective advantage for the growth of strict and facultative anaerobic LAB [ 7 , 8 , 12 , 30 ]. The observation of a plateau in LAB growth when the limit of 7.4 log10 CFU/g was exceeded could be attributed to acid production and nutrient depletion, as previously reported when LAB counts reached 8.0 or 9.0 log 10 CFU/g [ 5 , 33 ].…”

“…gasicomitatum , L. curvatus , C. divergens , which are known to form slime and produce acidic or buttery off-flavors [ 10 ]. Both species were identified as part of a raw meat psychrotrophic microbiota identified in meat during the tumbling process, following their isolation in cooked ham [ 12 ]. It was surprising to observe the absence of microbial growth during the 20 days of storage of cooked ham lot 6.…”

“…The most frequently isolated strains included Leuconostoc carnosum (Leuc) PFGE types Leuc 2, Leuc 3, and Latilactobacillus sakei (Sakei) PFGE types Sakei 3 and Sakei 4, which were both present in raw meat and the post-cooking area of the FPE. Prior studies have addressed the impact of raw meat and FPE on the composition of the final microbiota in cooked ham mainly by 16S rRNA gene profiling and by culture-dependent methods [ 9 , 11 , 12 , 16 , 19 , 20 ]. However, the present study provides confirmation of these observations at the strain level.…”

“…Although the cooking step at a core temperature of ≥70 °C reduces the bacterial load close to the detection limit of the used microbiological methods, some thermoduric LAB species, enterococci, and other microbes may survive this process [ 10 ]. Furthermore, there is a risk of product recontamination with spoilage-associated bacteria in the post-cooking area during cooling, slicing, and packaging [ 11 , 12 ]. To counteract this, cooked ham is typically vacuum packed and refrigerated to prevent the growth of Gram-negative spoilage bacteria such as Pseudomonas and Enterobacteriaceae spp.…”

“…gelidum , Latilactobacillus ( Lb .) sakei from FPE and demonstrated their presence in cooked ham as a result of cross-contamination events from raw meat in the pre- and post-cooking areas of the FPE [ 9 , 11 , 12 , 16 , 19 , 20 ]. Furthermore, a slicing machine has been identified as a critical point for the introduction of LAB into cooked ham [ 9 ].…”