Laboratory of Food Microbiology and Food Preservation, Member of Food2know, Department of Food Safety and Food Quality, Ghent University, Coupure Links 653, 9000 Ghent, Belgium.
Food Microbiol. 2012 Dec;32(2):437-43. doi: 10.1016/j.fm.2012.07.011. Epub 2012 Aug 7.
The major objective of this study was to determine the role of psychrotrophic lactic acid bacteria (LAB) in spoilage-associated phenomena at the end of the shelf-life of 86 various packaged (air, vacuum, modified-atmosphere) chilled-stored retail food products. The current microbiological standards, which are largely based on the total viable mesophilic counts lack discriminatory capacity to detect psychrotrophic LAB. A comparison between the total viable counts on plates incubated at 30 °C (representing the mesophiles) and at 22 °C (indicating the psychrotrophs) for 86 food samples covering a wide range - ready-to-eat vegetable salads, fresh raw meat, cooked meat products and composite food - showed that a consistent underestimation of the microbial load occurs when the total aerobic mesophilic counts are used as a shelf-life parameter. In 38% of the samples, the psychrotrophic counts had significantly higher values (+0.5-3 log CFU/g) than the corresponding total aerobic mesophilic counts. A total of 154 lactic acid bacteria, which were unable to proliferate at 30 °C were isolated. In addition, a further 43 with a poor recovery at this temperature were also isolated. This study highlights the potential fallacy of the total aerobic mesophilic count as a reference shelf-life parameter for chilled food products as it can often underestimate the contamination levels at the end of the shelf-life.
本研究的主要目的是确定低温嗜热乳酸菌（LAB）在 86 种不同包装（空气、真空、改良气氛）冷藏零售食品保质期结束时与变质相关现象中的作用。目前的微生物标准主要基于总可培养需氧中温菌计数，缺乏区分能力来检测低温嗜热 LAB。对涵盖广泛范围的 86 种食品样品（即即食蔬菜沙拉、新鲜生肉、熟肉制品和复合食品）的平板总活菌计数在 30°C（代表中温菌）和 22°C（代表低温菌）下进行比较，结果表明，当总需氧中温菌计数用作保质期参数时，微生物负荷会一直被低估。在 38%的样品中，低温菌计数比相应的总需氧中温菌计数显著更高（+0.5-3 对数 CFU/g）。共分离出 154 株不能在 30°C 下增殖的乳酸菌，此外，还分离出 43 株在该温度下回收效果较差的乳酸菌。本研究强调了总需氧中温菌计数作为冷藏食品保质期参考参数的潜在谬误，因为它往往会低估保质期结束时的污染水平。
