Evaluation of High Hydrostatic Pressure as an Alternative Method for Camel Milk Preservation

Abstract

In this work, high hydrostatic pressure was applied to preserve camel milk. It is used as an alternative method to heat treatment which usually damage some nutrient components of milk. Fresh samples were subjected to pressure treatments at 200-600 Megapascals (MPa) for 5 minutes and 40°C. Treatment at 200 MPa reduced microbial contamination up to 0.12 log cycles. The killing effect increased with increased pressure to exceed three log cycles at pressures up to 400 MPa. Gram negative bacteria were more affected by high pressure treatments that gram positive ones. Enterobacteriaceae can be controlled by pressure treatments up to 300 MPa. Pressure treatments up to 350 MPa can cause clotting of camel milk, a phenomenon not observed in cow or goat milk and also not observed in camel milk at heat treatment up to boiling. Camel milk treated at 300 MPa and stored at 3ºC showed no signs of microbial spoilage up to 15 days of storage, while the microbial load of untreated samples stored at the same temperature reached the spoilage level in about a week. High pressure treatment of camel milk resulted in a decrease in its proteolytic activity, but had no significant effect on other chemical attributes such as color, fat oxidation, pH value and the organoleptic characteristics. High hydrostatic pressure up to 300 MPa can be successfully used to preserve camel milk against microbial spoilage. The phenomenon of camel milk clotting at pressures above 300 MPa needs investigation.