Monitoring and modelling of headspace-gas concentration changes for shelf life control of a glass packaged perishable food

Gas concentrations in the headspace of hermetically sealed glass packages of seasoned soybean sprouts were monitored and related to their microbial quality, i.e., the change in aerobic bacterial count, in order to examine the potential for using package gas changes as a primary quality index for shelf life control. Aerobic bacterial count, CO₂ and O₂ concentrations were measured from packages stored at four different temperatures: 0, 5, 10 and 15 °C. The CO₂ concentration increased and the O₂ concentration decreased with microbial growth. The microbial growth and CO₂ concentration change were described by a logistic function to yield kinetic parameters, and their temperature dependence was analysed by a square-root model. The kinetic parameters for microbial growth and CO₂ production differed in their magnitude and temperature dependence. The lag time observed for the increase in CO₂ concentration could be used as a shelf life index that corresponds to the time to reach a given microbial limit (here, 10⁷ CFU/g) under different temperature conditions, particularly under conditions of temperature abuse.