Mechanisms of food microbial growth and quality changes under low temperature storage conditions

In this paper, the growth dynamics of microorganisms such as coliforms, molds, lactobacilli, Staphylococcus aureus and Salmonella were studied under different low-temperature storage conditions using milk tofu and milk skins as test subjects. The square root equation of the growth kinetic parameters of temperature and total number of colonies was calculated. Environmental factors such as O₂ concentration and CO₂ concentration were introduced to jointly establish a secondary model for the growth of total bacterial counts and verify its effectiveness. Use the model to analyze the inhibitory effect of low-temperature storage on the growth of food microorganisms and its correlation with shelf-life. The maximum values of coliform counts of milk tofu and milk skin were 21 CFU/g and 72 CFU/g at -6℃ for 18 days, respectively. The mold counts of milk tofu exceeded the standard range from the 12th day. The mold counts of most of the milk skin samples exceeded the standard range for the different low temperature conditions and time periods measured. Lactic acid bacteria counts increased with time duration and temperature. Staphylococcus aureus and Salmonella spp. were not detected. There was no interaction effect of O₂ concentration and CO₂ concentration in the variation of growth kinetic parameters of total bacterial population. The deviation of the model fit was 0.998 and the accuracy was 1.002. The correlation coefficients of the growth kinetic parameters of microorganisms with the microbial shelf-life and sensory shelf-life were r=0.65, which was a weak correlation.