Effect of irradiation of frozen meat/fat trimmings on microbiological and physicochemical quality attributes of dry fermented sausages.

Changes in microbiological and physicochemical quality attributes resulting from the use of irradiation in the production of Greek dry fermented sausage were investigated as a function of fermentation/ripening time. Results showed that irradiating meat/fat trimmings at 2 or 4kGy prior to sausage production eliminated natural contamination with Listeria spp., and reduced pseudomonads, enterococci and pathogenic staphylococci, and enterobacteria, to less than 2 and 1logcfug(-1), respectively. Pseudomonads were very sensitive (>3.4 log reduction) to either radiation dose. Yeasts were the most resistant followed by inherent lactic acid bacteria; their reductions on the trimmings were radiation dose-dependent. Residual effects of irradiation were noted against enterococci, but not against gram-negatives which died off fast during fermentation even in non-irradiated samples. Growth of the starter bacteria, Lactobacillus pentosus and Staphylococcus carnosus, inoculated in the sausage batters post-irradiation was unaffected by the 2 or 4kGy pre-treatment of the trimmings. Irradiation had little or no effect at the end of ripening period (28 days) on pH, moisture content and color (parameters L(∗), a(∗), and b(∗)). Changes in TBA values were small but statistically significant with irradiated samples having higher TBA values than control samples.

Shelf-life of a chilled precooked chicken product stored in air and under modified atmospheres: microbiological, chemical, sensory attributes.

This study evaluated the effect of modified atmosphere packaging on shelf-life extension of a precooked chicken meat product stored at 4 degrees C using microbiological, physico-chemical and sensory analyses. The following gas mixtures were used: M1: 30%/70% (CO2/N2), M2: 60%/40% (CO2/N2) and M3: 90%/10% (CO2/N2). Identical chicken samples were aerobically packaged and used as control samples. Sampling was carried out at predetermined time intervals namely: 0, 4, 8, 12, 16 and 20 days. Total viable counts (TVC), Lactic acid bacteria (LAB), Brochothrix thermosphacta, pseudomonads, yeasts and molds, and Enterobacteriaceae were monitored. TVC of precooked chicken product reached 7 log cfu/g, after days 12 and 16 of storage (air and M1 samples), respectively. The M2 and M3 gas mixture packaged samples did not reach this value throughout the 20 days storage period under refrigeration. LAB and to a lesser degree B. thermosphacta, constituted part of the natural microflora of precooked chicken samples stored in air and under MAP reaching 7.0-8.1 log cfu/g at the end of storage period. Of the remaining bacterial species monitored, both pseudomonads and yeasts/molds were significantly higher (P<0.05) for chicken samples stored in air than under MAP (M1, M2, M3) throughout the entire storage period under refrigeration. Finally, counts of Enterobacteriaceae were low (<2 log cfu/g) in all chicken samples irrespective of the packaging conditions throughout the entire storage period. Of the chemical indices determined, thiobarbituric (TBA) values in all cases remained low, equal or lower than 3.0 mg malonaldehyde (MA)/kg during the entire storage period. Results of the present work show that the limit of sensory acceptability was only reached for the aerobically stored and M1 gas mixture chicken samples somewhat before days 16 and 20 of storage, respectively. This limit coincided with high TVC and LAB populations (>6.8 log cfu/g), increased lipid oxidation (aerobic storage only) and apparent growth of yeasts/moulds on the surface of chicken samples. The use of MAP as shown in the present study, resulted in an extension of shelf-life of precooked chicken by ca. 4 days (M1 gas mixture), and by more than 6 days (M2 and M3 gas mixtures), respectively. Precooked chicken meat was better preserved under M2 and M3 mixtures maintaining desirable odor/taste attributes even on final day of storage tested.

Microbiological, biochemical and sensory assessment of mussels (Mytilus galloprovincialis) stored under modified atmosphere packaging.

AIMS: To determine the microbiological, biochemical and sensory changes of mussels during storage under aerobic, vacuum packaging (VP) and modified atmosphere packaging (MAP) conditions at 4 degrees C, and to determine shelf-life of mussels under the same packaging conditions using the above assessment parameters. METHODS AND RESULTS: Aqua-cultured mussels (Mytilus galloprovincialis) were obtained from a local culture farm, packaged aerobically under VP and MAP (50%/50% CO2/N2: M1, 80%/20% CO2/N2: M2, 40%/30%/30% CO2/N2/O2: M3), and stored at 4 degrees C. Quality evaluation was carried out using microbiological, chemical and sensory analyses. Microbiological results revealed that the M2 and VP delayed microbial growth compared with that of air-packaged samples. The effect was more pronounced for total viable count (TVC), Pseudomonas spp., lactic acid bacteria (LAB) and H2S-producing bacteria. TVC was reduced by 0.9-1.0, Pseudomonas spp. by 0.7-0.8, LAB by 1.0-2.2, H2S-producing bacteria by 0.7-1.2. Enterobacteriaceae were not significantly affected by MAP conditions. Of the chemical indices determined, the total volatile basic nitrogen and trimethylamine nitrogen values remained lower than the proposed acceptability limits of 35 mg N 100 g(-1) and 12 mg N 100 g(-1), respectively, after 15 days of storage. Both the VP and air-packaged mussel samples exceeded these limits. The thiobarbituric acid value of all MAP and VP mussels remained lower than the proposed acceptability limit of 1 mg malondialdehyde kg(-1). The air-packaged samples exceeded this limit. All samples retained desirable sensory characteristics during the first 8 days of storage. CONCLUSIONS: Based on odour and taste evaluation, the M1 and M3 samples remained acceptable until ca day 11-12, the M2 samples remained acceptable until ca day 14-15 days while the VP and air-packaged mussel samples remained acceptable until ca days 10-11 and 8-9 of storage respectively. Based primarily on sensory, but also on biochemical and microbiological parameters determined, M2 gas mixture was the most effective for mussel preservation achieving a shelf-life of ca 14-15 days. SIGNIFICANCE AND IMPACT OF THE STUDY: MAP (M2) can be used to increase the shelf-life of refrigerated mussels. A shelf-life extension of refrigerated mussels by ca 5-6 days under MAP may be obtained.