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.

Use Carum copticum essential oil for controlling the Listeria monocytogenes growth in fish model system

This study was conducted to evaluate the antibacterial effect of Carum copticum essential oil (Ajowan EO) against Listeria monocytogenes in fish model system. Ajowan EO chemical composition was determined by gas chromatography/mass spectral analysis and the highest concentration of Carum copticum essential oil without any significant changes on sensory properties of kutum fish (Rutilus frisii kutum) was assigned. Then the inhibitory effect of Ajowan EO at different concentrations in presence of salt and smoke component was tested on L. monocytogenes growth in fish peptone broth (FPB), kutum broth and cold smoked kutum broth at 4 ºC for 12 days. Ajowan EO completely decreased the number of L. monocytogenes in FPB after 12 days of storage, however, antimicrobial effect of EO significantly reduced in kutum and cold smoked kutum broth. Addition of 4% NaCl and smoke component improved the anti-listerial activity of Ajowan EO in all fish model broths.

Combination of Origanum vulgare L. essential oil and lactic acid to inhibit Staphylococcus aureus in meat broth and meat model

This study assessed the occurrence of an enhancing inhibitory effect of the combined application of Origanum vulgare L. essential oil and lactic acid against Staphylococcus aureus by the determination of Fractional Inhibitory Concentration (FIC) index and cell viability in meat broth and meat model. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of the oil was 0.6 and 1.25 µL.mL-1, respectively. Lactic acid showed MIC and MBC of 2.5 and 5µL.mL-1, respectively. FIC indices of the combined application of the oil and lactic acid were 0.5 showing a synergic interaction. The essential oil and lactic acid showed similar (p>0.05) anti-S. aureus effect in meat broth over 96 h of exposure. Treatment with essential oil or lactic acid presented a smaller anti-staphylococcal effect in meat in comparison to meat broth. No significant difference (p>0.05) was found for the microbial counts in meat treated with each antimicrobial alone or in mixture. These results could arise as an interesting approach for the improvement of food preservation using more natural procedures, considering the current demand of consumer and sensory quality of foods.