The influence of modified atmosphere packaging on shelf life of ćevapčići

The aim of this study was to determine the microbiological, sensory and chemical changes of modified atmosphere packaged ćevapčići in a gas mixture consisting of 70% O2 and 30% CO2. Packaged ćevapčići were stored for 10 days at 3ºC. Microbiological examination comprised determination of pathogenic microorganisms (Salmonella spp., coagulase positive staphylococci, Escherichia coli and Listeria monocytogenes) as well as indicators of hygiene and spoilage (total viable count, psychrotrophic bacteria, Enterobacteriaceae, lactic acid bacteria and Brochothrix thermosphacta). Using quantitative-descriptive test with grading scales from one to five, sensory properties of ćevapčići were assessed (color and odor in raw condition and odor, texture and taste after roasting) on the 1st, 4th, 6th, 8th and 10th days of storage. Regarding the chemical parameters, every day during the storage, pH was examined and on 4th and 8th days, acid value and peroxide number were established. On the basis of the results obtained and the recommended total viable count, which should not be higher than 7 log cfu/g, and taking into consideration sensory properties, we can conclude that ćevapčići packed in the modified atmosphere containing 70 % O2 and 30% CO2 had a shelf life of seven days.

Natural Methoxyphenol Compounds: Antimicrobial Activity against Foodborne Pathogens and Food Spoilage Bacteria, and Role in Antioxidant Processes

The antibacterial and antioxidant activities of three methoxyphenol phytometabolites, eugenol, capsaicin, and vanillin, were determined. The in vitro antimicrobial potential was tested on three common foodborne pathogens (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus) and three food spoilage bacteria (Shewanella putrefaciens, Brochothrix thermosphacta, and Lactobacillus plantarum). The antioxidant assays were carried out for studying the free radical scavenging capacity and the anti-lipoperoxidant activity. The results showed that eugenol and capsaicin were the most active against both pathogens and spoilage bacteria. S. aureus was one of the most affected strains (median concentration of growth inhibition: IC50 eugenol = 0.75 mM; IC50 capsaicin = 0.68 mM; IC50 vanillin = 1.38 mM). All phytochemicals slightly inhibited the growth of L. plantarum. Eugenol was the most active molecule in the antioxidant assays. Only in the oxygen radical absorbing capacity (ORAC) test did vanillin show an antioxidant activity comparable to eugenol (eugenol ORAC value = 2.12 ± 0.08; vanillin ORAC value = 1.81 ± 0.19). This study, comparing the antimicrobial and antioxidant activities of three guaiacol derivatives, enhances their use in future applications as food additives for contrasting both common pathogens and spoilage bacteria and for improving the shelf life of preserved food.

Quantification of Viable Brochothrix thermosphacta in Cold-Smoked Salmon Using PMA/PMAxx-qPCR

The aim of this study was to develop a rapid and accurate PMA-qPCR method to quantify viable Brochothrix thermosphacta in cold-smoked salmon. B. thermosphacta is one of the main food spoilage bacteria. Among seafood products, cold-smoked salmon is particularly impacted by B. thermosphacta spoilage. Specific and sensitive tools that detect and quantify this bacterium in food products are very useful. The culture method commonly used to quantify B. thermosphacta is time-consuming and can underestimate cells in a viable but not immediately culturable state. We designed a new PCR primer set from the single-copy rpoC gene. QPCR efficiency and specificity were compared with two other published primer sets targeting the rpoC and rpoB genes. The viability dyes PMA or PMAxx were combined with qPCR and compared with these primer sets on viable and dead B. thermosphacta cells in BHI broth and smoked salmon tissue homogenate (SSTH). The three primer sets displayed similar specificity and efficiency. The efficiency of new designed rpoC qPCR on viable B. thermosphacta cells in SSTH was 103.50%, with a linear determination coefficient (r2) of 0.998 and a limit of detection of 4.04 log CFU/g. Using the three primer sets on viable cells, no significant difference was observed between cells treated or untreated with PMA or PMAxx. When dead cells were used, both viability dyes suppressed DNA amplification. Nevertheless, our results did not highlight any difference between PMAxx and PMA in their efficiency to discriminate viable from unviable B. thermosphacta cells in cold-smoked salmon. Thus, this study presents a rapid, specific and efficient rpoC-PMA-qPCR method validated in cold-smoked salmon to quantify viable B. thermosphacta in foods.

The Microbiota of Modified-Atmosphere-Packaged Cooked Charcuterie Products throughout Their Shelf-Life Period, as Revealed by a Complementary Combination of Culture-Dependent and Culture-Independent Analysis

Although refrigeration and modified-atmosphere packaging (MAP) allow for an extended shelf life of cooked charcuterie products, they are still susceptible to bacterial spoilage. To obtain better insights into factors that govern product deterioration, ample information is needed on the associated microbiota. In this study, sliced MAP cooked ham and cooked chicken samples were subjected to culture-dependent and culture-independent microbial analysis. In total, 683 bacterial isolates were obtained and identified from 60 samples collected throughout the storage period. For both charcuterie types, lactic acid bacteria (LAB) constituted the most abundant microbial group. In cooked ham, Brochothrix thermosphacta was highly abundant at the beginning of the shelf-life period, but was later overtaken by Leuconostoc carnosum and Lactococcus piscium. For cooked chicken products, Latilactobacillus sakei was most abundant throughout the entire period. Additionally, 13 cooked ham and 16 cooked chicken samples were analyzed using metabarcoding. Findings obtained with this method were generally in accordance with the results from the culture-dependent approach, yet they additionally demonstrated the presence of Photobacterium at the beginning of the shelf-life period in both product types. The results indicated that combining culture-dependent methods with metabarcoding can give complementary insights into the evolution of microorganisms in perishable foods.

Impact of a Combination of UV-C Irradiation and Peracetic Acid Spray Treatment on Brochothrix thermosphacta and Yersinia enterocolitica Contaminated Pork

Efficient ways of decontamination are needed to minimize the risk of infections with Yersinia (Y.) enterocolitica, which causes gastrointestinal diseases in humans, and to reduce the numbers of Brochothrix (B.) thermosphacta to extend the shelf-life of meat. While many studies have focused on a single treatment of peracetic acid (PAA) or UV-C-irradiation, there are no studies about a combined treatment on meat. Therefore, in the present study, pork was inoculated with either Y. enterocolitica or B. thermosphacta, and was treated with a combination of 2040 mJ/cm2 UV-C irradiation followed by a 2000 ppm PAA spray treatment (30 s). Samples were packed under modified atmosphere and stored for 1, 7, or 14 days. The samples were examined for Y. enterocolitica and B. thermosphacta content, chemical and sensory effects, and meat quality parameters. For Y. enterocolitica, a significant reduction of up to 2.16 log10 cfu/cm2 meat and for B. thermosphacta, up to 2.37 log10 cfu/cm2 meat was seen on day 14 after UV-C/PAA treatment compared to the untreated controls.

Influence of antioxidative and antibacterial activity of sage aqueous extract and chitosan formulation on chicken burger quality

The aim of the present study was to assess the antioxidative and antibacterial activity of sage (Salvia officinalis L.) aqueous extract and chitosan formulation in chicken burgers during storage. Four burger treatments were prepared: C – without sage extract and chitosan formulation, S – with 2.0% of sage extract, CH – with 1.0% of chitosan formulation, and SCH – with 2.0% of sage extract and 1.0% of chitosan formulation. On the production day, the chemical composition of poultry burgers was analyzed. After 0, 7 and 14 days of storage in burgers, the advancement of the lipid oxidation process was assessed and microbiological analyses were performed. Microbiological analyses included the determination of the total count of mesophilic aerobic microorganisms and that of psychrotrophic bacteria, count of coliform bacteria, count of Pseudomonas, and count of lactic acid bacteria. One of the tested groups of bacteria was Brochothrix thermosphacta, which can cause spoilage of packaged meat products stored under refrigeration temperature. It has been found that aqueous sage extract had significantly (p <0.05) the best antioxidative effect compared to chitosan and the combination of sage extract and chitosan formulation in chicken burgers during the entire storage period. Both aqueous sage extract and chitosan formulation exhibited antibacterial activity in chicken burgers, although the efficiency of growth inhibition differed between the tested bacteria groups. After 14 days of storage of burgers, the significantly (p <0.05) lowest number of mesophilic aerobic microorganisms, Pseudomonas spp., and B. thermosphacta were found in burgers with the combination of sage extract and chitosan formulation.