Determination of CO2 Content in the Headspace of Spoiled Yogurt Packages

The CO2 formation during food storage can often be correlated with the increase in yeast population. Yogurt and other dairy products are susceptible to yeast contamination. Accumulation of CO2 in the headspace of yogurt packages can lead to the eventual blowing off of the package. Therefore, determination of CO2 in the yogurt packages can indicate eventual unsafety of the product. The aim of this paper was to determine CO2 concentration in the headspace of different yogurt containers contaminated with yeast at the levels of 1 and 5 CFU/ml. Yeast Candida kefyr, previously isolated from spoiled yogurt, was used for contamination. Contaminated and control samples of yogurt were incubated at 30°C. A device based on tunable diode laser absorption spectroscopy was used for the measurement of CO2 concentration. The CO2 content in all analysed samples changed in a similar manner with slow increase to the value of 6% during the first 30 h and, after that, rapid accumulation to 17–20%. The initial level of yeast contamination did not have significant influence to the CO2 content trend. The increase in the number of yeast was observed after 10 h of incubation, and the final value of 6-7 log·CFU/cm3 was reached after 40 h of incubation. The significant increase in the yeast number can be correlated with the CO2 content in a way that CO2 concentration of 6% can be considered as critical for microbial spoilage. Since the TDLAS technique is simple and nondestructive, it can be a promising possibility for detection of the microbial spoilage in food.