Abstract
The aim of the present study was to investigate the evolution of the volatile compounds of aerobically stored sterile pork meat as a consequence of the metabolic activities of inoculated specific spoilage microorganisms. Thus, Pseudomonas fragi, Pseudomonas putida, Lactobacillus sakei and Leuconostoc mesenteroides were inoculated in monocultures, dual cultures and a cocktail culture of all strains on sterile pork meat stored aerobically at 4 and 10 °C. Microbiological and sensory analyses, as well as pH measurements, were performed, along with headspace solid-phase microextraction gas chromatography/mass spectroscopy (headspace SPME–GC/MS) analysis. Data analytics were used to correlate the volatile compounds with the spoilage potential of each stain using multivariate data analysis. The results for the sensory discrimination showed that the volatiles that dominated in spoiled samples consisted mostly of alcohols, ketones and two esters (butyl acetate and ethyl acetate), while at fresh samples, dimethyl sulfide, furans, acetoin and ethyl lactate were detected. On the other hand, 2-butanone, diacetyl and acetaldehyde were among the volatile compounds that were mainly correlated with the inoculated meat during storage. In addition, P. fragi was positively correlated with a higher number of volatiles compared to the other strains, strengthening the hypothesis that volatile compound production is strain-dependent.
Highlights
It is well-established that pseudomonads, lactic acid bacteria (LAB), Enterobacteriaceae, Brochothrix thermosphacta and clostridia are the main contributors to meat spoilage, depending on storage conditions [1,2,3,4,5]
In detail, regarding the pork samples inoculated with monocultures of the strains, results showed that at 4 ◦ C P. fragi reached the highest population level at the end of storage (9.33 ± 0.18 log CFU/g), while the lag phase of this strain was the shortest compared to the other monocultures (Table 1)
For the inoculated meat samples with dual and cocktail cultures at the same temperature, the population of P. fragi and P. putida was ≥ 8.79 log CFU/g in all cases (8.79 ± 0.42 and 9.13 ± 0.97 log CFU/g for dual and cocktail cultures, respectively), while the LAB populations remained at lower levels (5.10 ± 0.25 and 5.72 ± 0.43 log CFU/g for the dual and cocktail culture, respectively)
Summary
It is well-established that pseudomonads, lactic acid bacteria (LAB), Enterobacteriaceae, Brochothrix thermosphacta and clostridia are the main contributors to meat spoilage, depending on storage conditions [1,2,3,4,5]. Species of the genus pseudomonas are recognized more often as causative agents of spoilage on fresh foods of animal origin stored under aerobic conditions [6]. LAB and B. thermosphacta have been found to contribute in meat spoilage stored either under aerobic, modified atmosphere packaging (MAP) or vacuum packaging (VP). In this case, the most frequently isolated species are Lactobacillus spp., Carnobacterium spp. and Leuconostoc spp.
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