Determination of CO2 Content in the Headspace of Spoiled Yogurt Packages
Danilović, Bojana | Savić, Dragiša | Cocola, Lorenzo | Fedel, Massimo | Poletto, Luca
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.
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