INCREASING SHELF LIFE BY CARBON DIOXIDE TREATMENT AND LOW TEMPERATURE STORAGE OF BULK PACK FRESH CHICKENS PACKAGED IN NYLON/SURLYN FILM

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Abstract
Simulated commercial bulk pack, whole chickens were subjected to conventional ice pack and three modified atmospheric, vacuum and two levels of CO2 within a Nylon/Surlyn film, storage environments. Pathogenic and nonpathogenic microbial growth, void space gas composition (except ice pack) and off‐odor development were monitored on samples stored at 1.1°C. Polynomial regression analysis of aerobic growth curves revealed that the lag phase was extended to 8‐10 days by using a CO2 addition rate of 3.61 × 10‐4 and 7.22 × 10‐4 m3/kg, respectively. The transition from lag to log phase appeared when the residual level of CO, in the void space reached 15‐55%. Following initial replacement of the air in the pouch with 95% CO2, the growth of anaerobic microorganisms was limited by the presence of CO2. The growth of potential pathogens, salmonella, coliforms, Staphylococcus aureus and Clostridium perfringens in the presence or absence of CO2 was negligible at 1.1°C. Off‐odor development can be detected when the colony forming units (CFU) numbers reach 106/g of body weight. Carbon dioxide restricts the growth of most objectionable putrefactive off‐odor bacteria; lactic acid organisms are encouraged by its presence on the surface of the sample and in the pouch void space. A recommended usage rate of 7.22 × 10‐4 m3 CO2/kg of body weight extends shelf life quality to 27 days at 1.1°C.