Formation and Cumulation of CO2 in the Bottles of the Fermented Milk Drinks

Abstract

Abstract. As in majority of food during storage, the development of CO 2 in headspace of yogurt is mainly the result of contamination and yeast growth. Thitherto, the monitoring of the changes of CO 2 concentration in the yogurt package"s atmosphere can be an indicator of the product quality and safety. The aim of this paper is to determine the accumulation of the CO 2 in the headspace of bottles of fermented milk products: yogurt ""Vedro 2.8% milk fat"" and fermented milk drink with probiotics ""FidoBe 0.5% milk fat"", both produced in ""Niška mlekara"", AD Niš, Serbia. To examine these phenomena, the products were incubated at 30 o C and contaminated with yeast at the levels of 1 and 5 CFU/ml. The strain of yeast used for the contamination was isolated from the spoiled yogurt. During the incubation, the CO 2 measurements were continuously performed with a device specially constructed for this purpose. The instrument was based on Tunable Diode Laser Absorption Spectroscopy with a Wavelength Modulation Spectroscopy technique. The number of lactic acid bacteria and the number of yeasts were monitored, too. Also the pH value was measured. The content of CO 2 in the headspace of contaminated (initial yeast concentration -1 CFU/ml) bottles of yogurt ""Vedro"" slightly increased from the start value to cca 5,0% at the 30th hour of incubation reaching yeast level of cca 4 logCFU/ml. After that, the CO 2 content and the number of yeasts increased faster until the 40th h and reached the values of cca. 16% and 6 logCFU/ml, respectively. During the incubation of the contaminated bottles of fermented milk drink ""FidoBe"", the CO 2 level slightly increased from the initial cca 1% to cca 5% during 36 h in bottles contaminated with 1 CFU/ml, and after 30 h in the bottles contaminated with 5 CFU/ml. Hereupon, the increase of CO 2 content was faster reaching 20% after 40h in experiment with the initial 5 CFU/ml yeasts, and after 48h in experiment with the initial 1 CFU/ml of yeast. During the incubation, the yeast level increased until the final level of 6.0 logCFU/ml.

Determination of CO2 Content in the Headspace of Spoiled Yogurt Packages

“…According to the results, the CO 2 content above 6% can be considered critical for microbial spoilage since at this point the level of detected number of yeast is significant. is confirmed our previous state [20,24] that this content of CO 2 in the headspace of fermented milk products is an indicator of possible contamination.…”

“…e yogurt samples were contaminated with the yeast Candida kefyr at two levels of initial cell concentrations: 1 CFU/cm 3 (bottles) and 5 CFU/cm 3 (cups and bottles). In order to discuss and compare changes in the CO 2 content in the headspaces of two types of yogurt, the results of the previous experiment [20] with the bottles (500 g) contaminated at the initial level of 1 CFU/cm 3 are also included.…”

Super-Earths, M Dwarfs, and Photosynthetic Organisms: Habitability in the Lab

“…Vital photosynthetic microorganisms in a liquid medium inside the cell are expected to produce oxygen. Hence, the cell is provided with a commercial fluorescence quenching oxygen sensor (Nomasense O P300), while the CO concentration is monitored via a custom Wavelength Modulation Spectroscopy (WMS) Tunable Diode Laser Absorption Spectroscopy (TDLAS, [ 58 ]) set up. To monitor the gas, four wedged windows of 2.5 cm are pierced and paired two by two in opposite positions on the wall of the cell.…”

Super-Earths, M Dwarfs, and Photosynthetic Organisms: Habitability in the Lab

“…Vital photosynthetic microorganisms in a liquid medium inside the cell are expected to produce oxygen. Hence, the cell is provided with a commercial fluorescence quenching oxygen sensor (Nomasense O 2 P300), while the CO 2 concentration is monitored via a custom Wavelength Modulation Spectroscopy (WMS) Tunable Diode Laser Absorption Spectroscopy (TDLAS, [58]) set up. To monitor the gas, four wedged windows of 2.5 cm are pierced and paired two by two in opposite positions on the wall of the cell.…”