Evaluating the Effectiveness of Low Pressure Carbon Dioxide as a Hurdle in Raw Milk Storage

Aims: To evaluate the effectiveness of low pressure carbon dioxide as a hurdle in raw milk storage. Study Design: Milk samples were stored at under low pressure carbon dioxide at 29°C for 6 hours and the microbial quality of milk was compared with control milk. Place and Duration of Study: Department of Dairy Microbiology, Verghese Kurien Institute of Dairy and Food Technology (VKIDFT), Kerala Veterinary and Animal Sciences University, Mannuthy between January 2020 and December 2020. Methodology: Milk samples were collected from an organized farm. The initial microbial quality of milk was determined and samples were carbonated to a pressure of 20 psi and stored for six hours 29°C, uncarbonated milk sample kept at 29°C acted as the control. The microbial quality of the carbonated milk and uncarbonated milk was determined after storage in terms of total viable count, coliform count and gram negative organism count. Results: Significant growth suppression (P=0.05) of bacteria was observed in the carbonated milk. Total Viable count showed a suppression of 1.05 log cfu/ml while coliforms showed a suppression of 1.3 log cfu/ml. The greatest log reduction was observed in gram negative organisms with a difference of 2.2 log cfu/ml and psychrotrophic organisms with 1.54 log cfu/ml. Conclusion: Carbon dioxide was found to be an effective bacteriostatic agent which could be used for extending the keeping quality of raw milk. The bacteriostatic action could be due to anaerobic conditions developed by carbon dioxide and also due to the increased acidity of the medium.