The Bacterial Lethal Effect of Gaseous or Liquid CO2 in Raw Milk

Abstract: The consumer demands for high-quality, minimally-processed products that are microbiologically safehave been increased. Raw skim milk or pathogenic bacteria-inoculated sterilized milk was treated withgaseous or liquid (subcritical) CO2at different levels and stored at 4°C for 7 days.The bacterial reductionperformed by gaseous or liquid (subcritical) CO2, as nonthermal method, at different levels in raw milkwas compared to those of achieved by laboratory thermal pasteurization. The counts of standard platecount (SPC), coliforms and psychrotrophic bacteria were determined at 1, 3, 5 and 7 days of storageperiod in raw milk treatments and pasteurized milk. The pathogenic bacterial counts were determinedin inoculated sterilized milk during storage period. Changes in the pH values and sensorial propertiesof raw skim milk treated with different levels of gaseous or liquid CO2during storage at 4°C wereevaluated. The results showed that the SPC reduced till the 5th day of storage period with liquid CO2 atdifferent levels, while the SPC of control (without adding CO2) and gaseous CO2 treated raw milktreatments increased with prolonging storage period but the SPC growth rate of gaseous CO2 treatedraw milk treatments was lower than those of control allover storage period. The coliforms and psychrotrophic bacteria of liquid CO2– treated raw milks were lower than those of treated with gaseousCO2 along storage period. The liquid CO2 (28.17 mM) treated raw milk showed the absence of coliformsallover storage period and almost similar low counts of SPC and psychrotrophic bacteria to those of
pasteurized milk. The counts of different studied pathogenic strains inoculated in sterilized milk
declined with increasing liquid CO2 level and prolonging storage period. The counts of E. coli (twostrains) lowered, while S. aureus and B. cereus slightly increased with gaseousCO2. The pH slightlydecreased with increasing gaseous or liquid CO2levels and storage period. Off odors and coagulationare not recorded for liquid CO2 - raw milk treatments along storage period. Hence, the liquid CO2(28.17mM) can be used as effective method of storing bulk raw milk and as nonthermal method formilk pasteurization.
Publication year 2021
Pages 204-211
Availability location 2706 -7947
Availability number 2077- 4613
Organization Name
serial title Middle East Journal of Applied Sciences
Author(s) from ARC
Publication Type Journal