In order to find a convenient way to monitor and control the microbial quality and shelf life of chill-stored perishable foods, microbial growth and package headspace gas concentration changes were measured during storage of three foods (seasoned pork meat, Manila clam and seasoned spinach) at 10°C, and their interrelationship was investigated. Aerobic bacterial count was the highest among the measured counts of microbial groups including specific spoilage organisms and thus may be potentially used as an index of microbial spoilage of the foods. Spoilage bacterial growth on the foods accompanied O 2 depletion and CO 2 build-up in package headspace with some delay. There was a wide variation among the foods in the headspace package atmospheric change resulting from or related to microbial spoilage. Except for CO 2 production of Manila clam, lag times of the O 2 and CO 2 changes, determined by applying logistic function, amounted to 10 5.1 -10 7.3 CFU/g, which is in the range of the microbial quality limit commonly used for shelf life determination. Overall, lag times of gas concentration changes may be used as an indicator of shelf life periods of perishable foods to a limited extent.

Levels of carbon dioxide gas, a metabolite of microbial growth, have been reported to parallel the onset of microbial spoilage and may be used as a convenient index for a packaged food's shelf life. This study aimed to establish a kinetic model of CO2 production from perishable food for the potential use for shelf life control in the food supply chain. Aerobic bacterial count and package CO2 concentration were measured during the storage of seasoned pork meat at four temperatures (0, 5, 10 and 15 o C), and their interrelationship was investigated to establish a mathematical model. The microbial growth at constant temperature was described by using model of Baranyi and Roberts. CO2 production from the stored food could be explained by taking care of its yield and maintenance factors linked to the microbial growth. By establishing the temperature dependence of the microbial growth and CO2 yield factor, CO2 partial pressure or concentration in package headspace could be estimated to a limited extent, which is helpful for controlling the shelf life under constant and dynamic temperature conditions. Application and efficacy of the model needs to be improved with further refinement in the model.