Determination of CO₂ Content in the Headspace of Spoiled Yogurt Packages

Abstract

The CO 2 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 CO 2 in the headspace of yogurt packages can lead to the eventual blowing off of the package. Therefore, determination of CO 2 in the yogurt packages can indicate eventual unsafety of the product. The aim of this paper was to determine CO 2 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 CO 2 concentration. The CO 2 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 CO 2 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/cm 3 was reached after 40 h of incubation. The significant increase in the yeast number can be correlated with the CO 2 content in a way that CO 2 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.