Treatment of Raw Milk with CO2 - Effects on Microbial Characteristics and Self Life of Raw Milk

Treatment of raw milk with CO2 as a procedure for preventing of microbial growth, control of psychrotrophic bacteria and extending of self life of milk products was studied using normal raw milk, as control samples, and raw milks treated with CO2 up to pH = 6.4, 6.2 and 6. Experimental milk samples were stored for 10 days at 4◦C and used for microbial assessment at 1, 5, 8 and 10 days of storing. The experimental design was split plot based on randomized complete blocks with four replications. Results showed adding of CO2 to raw milk up to pH=6.2 and 6 inhibited significantly (P<0.05) microbial growth and those samples had a difference of 1.082 and 0.85 logarithmic unit in total count and also 1.089 and 0.923 in Psychrotrophic bacteria populations with control samples, respectively. It is concluded that adding of CO2 to raw milk up to pH= 6.2 and 6 can be considered as an effective pretreatment for preventing of increasing microbial population and preservation of raw milk. Samples treated by CO2 with pH=6 had a self life of 3 days longer than control samples and was selected as the most effective treatment, although there were not significant differences in most parameters between pH=6 and pH= 6.2.