Effect of high pressure treatment on starter bacteria and spoilage yeasts in fresh lactic curd cheese of bovine milk

The effect of high pressure treatment on the inactivation of starter bacteria and spoilage yeasts in a commercially manufactured fresh lactic curd cheese was investigated. Fresh cheeses made from pasteurised bovine milk using a commercial Lactococcus starter preparation were vacuum-packaged and subjected to high pressure treatment within the range of 200 to 600 MPa for 5 min at ambient temperature (≤ 22 °C), and subsequently stored at 4 °C for up to 8 weeks. The number of viable starter bacteria and spoilage yeasts were enumerated immediately after treatment and at time intervals of 1, 2, 3, 4, 6, and 8 weeks during refrigerated storage. The viable count of Lactococcus in the cheeses treated at 200, 300, 400, and 600 MPa, showed approximate reductions of 2, 5, 6, and 7 log units under aerobic incubation conditions; and 3, 5, 6, and 7 log units under anaerobic incubation conditions. Treatment at 200 MPa did not significantly prevent the growth of yeasts, but in samples subjected to pressures ≥ 300 MPa, the growth of yeasts was effectively controlled for 6 to 8 weeks.Industrial relevanceAustralian specialty cheese manufacturers are interested in extending the shelf-life of selected products to extend domestic distribution and to take advantage of export opportunities. The potential domestic and export market of fresh lactic curd cheese can be hampered by relatively short shelf-life. High pressure processing (HPP), under optimised conditions, can be utilised as an effective tool to extend shelf-life while maintaining the quality attributes of this product.