Influence of high pressure treatment on the acidification of bovine milk by lactic acid bacteria

On incubation at 30°C, high pressure (HP)-treated (600 MPa for 30 min) pasteurised whole bovine milk, inoculated with lactic acid bacteria (LAB; Lactococcus lactis subsp. lactis and cremoris), acidified faster than its unpressurised equivalent. Faster acidification of HP-treated milk was due to the faster growth of LAB, although the numbers of LAB after 6 h of incubation at 30°C were similar in unpressurised and HP-treated milk. The buffering capacity of the milk was influenced only slightly by HP treatment. Faster growth of LAB in HP-treated milk was possibly due to HP-induced increases in the level of non-sedimentable (non-micellar) caseins, thereby enhancing the supply of accessible nitrogen for bacteria. Enhanced growth of the LAB in, and resultant faster acidification of, HP-treated milk may indicate possible applications of HP treatment of milk in the manufacture of fermented dairy products, such as cheese and yoghurt.