Food Processing Center, University of Nebraska, Lincoln 68583.
Department of Food Science, Purdue University, West Lafayette, IN 47907.
J Dairy Sci. 2012 Sep;95(9):4851-4862. doi: 10.3168/jds.2011-5028.
The objective of this study was to determine the effectiveness of high-pressure processing to inactivate Listeria innocua (a Listeria monocytogenes surrogate) in Queso Fresco, and to study the effects of the high-pressure treatment on cheese-crumbling properties. Queso Fresco was made with pasteurized, homogenized milk, lactic acid bacterial starter culture, chymosin, and flake salt. Cheeses were pressed (0.1 MPa) for 1h before crumbling and inoculation with a cocktail of 3 strains of L. innocua, and then pressed for 12 h (0.1 MPa). High-pressure processing treatments of sliced cheese rounds included pressure from 400 to 600 MPa for 1 to 25 min. Cheese sample temperatures, initially approximately 21°C, increased during pressurization and decreased gradually during the holding time. The highest temperature increase was to 23.6°C at 600 MPa. Greater than 5-log reductions occurred at set-point pressures of 500, 550, or 600 MPa when held for at least 15, 3, or 1 min, respectively. However, because inactivation was neither complete nor permanent and crumbling properties were not maintained under the conditions tested in this study, high-pressure processing is not recommended for Queso Fresco applications.
本研究旨在确定高压处理对弗雷斯克干酪中无毒李斯特菌（李斯特菌单核细胞增生症的替代品）的灭活效果，并研究高压处理对奶酪易碎特性的影响。弗雷斯克干酪采用巴氏杀菌、均质牛奶、乳酸菌发酵剂、凝乳酶和片状盐制成。奶酪在压碎和接种 3 株无毒李斯特菌混合物之前（0.1 MPa）先压制 1 小时，然后再压制 12 小时（0.1 MPa）。高压处理的奶酪片包括在 400 至 600 MPa 的压力下处理 1 至 25 分钟。奶酪样品的温度最初约为 21°C，在加压过程中会升高，并在保持时间内逐渐降低。在 600 MPa 的压力下，温度最高升高到 23.6°C。在设定压力为 500、550 或 600 MPa 时，保持至少 15、3 或 1 分钟，分别可实现大于 5 个对数减少。然而，由于在本研究测试的条件下，灭活既不完全也不持久，并且易碎特性无法维持，因此不建议将高压处理用于弗雷斯克干酪的应用。
