Abstract
The effect of high-pressure processing (HPP) on Listeria monocytogenes, the indigenous microbiota and the shelf-life of chicken fillets was evaluated. Chicken fillets were inoculated with different inocula (2, 4, and 6 log CFU/g) of a 4-strain cocktail of L. monocytogenes, vacuum-packed, processed or not with HPP (500 MPa/10 min) and stored at 4 °C and 12 °C. Total viable counts (TVC), L. monocytogenes, Pseudomonas spp., Brochothrix thermosphacta, lactic acid bacteria (LAB), Enterobacteriaceae and yeasts/molds were determined along with the pH and sensory analysis. Pulsed-field gel electrophoresis (PFGE) was used to monitor the succession of indigenous Brochothrix isolates and inoculated Listeria strains. The main spoilage microorganism of HPP-treated samples was B. thermosphacta detected after 3 days of storage. HPP decreased the inoculated Listeria population. For the low and medium inoculum case it was detected throughout the shelf-life at both temperatures in populations near to the detection limit or after enrichment. In the high inoculum case, the pathogen decreased ≥5-log cycles after HPP, while increased subsequently to 1.6 and 4.5 log CFU/g at 4 °C and 12 °C, respectively, by the end of the shelf-life. PFGE showed that Brochothrix isolates exhibited a significant diversity among control samples, whereas this was limited for the HPP-treated samples. The survival and distribution of different Listeria strains depended on the initial inoculum and storage temperature. In conclusion, HPP increased the shelf-life (for 5 and 4 days, at 4 °C and 12 °C, respectively) and enhanced the safety of chicken meat.
Highlights
It is well established that poultry meat is a highly perishable food with a short shelf-life limited from 4 to 15 days under refrigeration, depending mostly on the packaging type used [1]
The microbiological results obtained in this study demonstrated similar or higher reductions in the population of indigenous microbiota after the application of high-pressure processing (HPP), as compared to literature findings of poultry products or other meat products treated with HPP
In the current work B. thermosphacta was found to be the dominant microorganism after HPP, a result that was observed by Argyri et al [25], while a small increase of Pseudomonas spp. and yeasts/molds at 4 ◦C and Pseudomonas and Enterobacteriaceae at 12 ◦C was observed after the end of the shelf-life of the HPP-treated chicken fillets
Summary
It is well established that poultry meat is a highly perishable food with a short shelf-life limited from 4 to 15 days under refrigeration, depending mostly on the packaging type used [1]. The metabolic activity of the specific microbiota leads to changes dependent on the availability of energy substrates i.e., low molecular weight compounds (glucose, lactate, amino acids, etc.) of meat and spoilage prevails because of accumulation of metabolic by-products [4,5]. B. thermosphacta is capable of growing at a wide range of pH (5–9), temperature (0–30 ◦C), or NaCl (up to 10%) and is thought to be a ubiquitous microorganism throughout the meat production chain [7]. It is responsible for spoilage of meat stored under aerobic, modified atmosphere packaging (MAP) or/and vacuum packaged conditions and can become the dominant microbiota leading to souring of the meat. Brochothrix can utilize glucose and produce unpleasant off-flavors, like cheesy odors responsible for a distinct type of meat spoilage [4,8]
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