INFLUENCE OF MODIFIED ATMOSPHERE PACKAGING ON GROWTH OF CLOSTRIDIUM PERFRINGENS IN COOKED TURKEY

Shelf-Life of Boiled Salted Duck Meat Stored Under Normal and Modified Atmosphere

The objective of this study was to investigate the physicochemical properties and changes in the microbial counts of boiled salted duck (BSD) meat packed under various conditions. BSD meat was stored under normal atmosphere (C) and two modified atmosphere packaging (MAP) conditions: M1 (N₂ , 100%) and M2 (CO₂ /N₂ , 30%/70%) at 4 °C. Microbiological quality, pH, redness, lipid oxidation, headspace gas composition, and water activity of BSD meat were measured. The results showed that the time to reach the maximum acceptable total viable counts (TVC, 4.9 log CFU/g) was 12, 18, and 21 d in C, M1, and M2 samples, respectively. Significant difference in the redness values was observed in all treatments during storage. The redness value of C group was significantly lower than that in M1 and M2 groups at the end of storage. The thiobarbituric acid-reactive substances (TBARS) values under MAP were 0.24 to 0.26 mg MDA/kg meat at the end of storage, lower (P < 0.05) than that in C group (0.78 mg MDA/kg meat). The water activity in M2 group was the lowest among all 3 groups. The CO₂ concentration in M2 decreased significantly during storage. Our study demonstrates that packaging with 30% CO₂ and 70% N₂ (M2) could extend the shelf-life of BSD meat to 21 d during storage at 4 °C, suggesting that MAP can be a practical approach to extend the shelf-life and maintain the quality of BSD products.

PRACTICAL APPLICATION

This study evaluated the application of MAP for a cooked duck product. Our results showed that MAP can be utilized to extend the shelf-life. This technology may be used for preservation of other cooked meat products.

Influence of several methodological factors on the growth of Clostridium perfringens in cooling rate challenge studies

Proper temperature control is essential in preventing Clostridium perfringens food poisoning. The U.S. Department of Agriculture Food Safety and Inspection Service cooling guidelines offer two options for the cooling of meat products: follow a standard time-temperature schedule or validate that alternative cooling regimens result in no more than a 1-log CFU/g increase of C. perfringens and no growth of Clostridium botulinum. The latter option requires laboratory challenge studies to validate the efficacy of a given cooling process. Accordingly, the objective of this study was to investigate the role of several methodological variables that might be encountered during typical C. perfringens challenge studies. Variables studied included plastic bag type (Whirlpak or Spiral Biotech), sealing method (Multivac or FoodSaver), initial spore inoculum size (1 to approximately 3 log CFU/g), and growth environment (ground beef or Trypticase-peptone-glucose-yeast extract [TPGY] broth). The major factors that affected growth were sample bag type and growth environment. Samples incubated in Whirlpak bags showed significantly less growth than those incubated in Spiral Biotech bags, which was likely due to the former bag's greater oxygen permeability. C. perfringens spores showed shorter germination, outgrowth, and lag times and C. perfringens cells showed faster growth rates in ground beef compared with TPGY broth. No significant difference was observed between two different sealing methods. Initial spore inoculum levels in the range studied had no significant effect on final C. perfringens cell concentration.

The effect of calcium and sodium lactates on growth from spores of Bacillus cereus and Clostridium perfringens in a 'sous-vide' beef goulash under temperature abuse

The effect of calcium and sodium lactates on growth from spores of Bacillus cereus and Clostridium perfringens at three different concentrations (0, 1.5 and 3% w/w) and at different temperatures (10, 15 and 20 degrees C for B. cereus and 15, 20 and 25 degrees C for C. perfringens) was investigated, using beef goulash as a model system for pasteurised vacuum-packaged convenience foods. Calcium lactate at a level of 3% reduced the pH values of the samples from 6.0 to 5.5. No B. cereus growth was observed at 10 degrees C, but after 7 days at an incubation temperature of 15 degrees C, cell number increased by 1 log cfu/g in the control samples. At this temperature, lactates were seen to be effective at inhibiting growth. Calcium lactate was more inhibitory than sodium lactate as the growth of B. cereus was inhibited at 1.5 and 3% concentrations at 20 degrees C, respectively. Growth of C. perfringens was arrested in the presence of 1.5% calcium lactate at all storage temperatures, whereas growth was inhibited by 3% sodium lactate only at 15 degrees C.