Wuytack E Y, Michiels C W
Laboratory of Food Microbiology, Katholieke Universiteit Leuven, Belgium.
Int J Food Microbiol. 2001 Mar 20;64(3):333-41. doi: 10.1016/s0168-1605(00)00478-5.
Bacillus subtilis spore suspensions were subjected to pressure treatments at 100 and 600 MPa at 40 degrees C and over a pH range from 3 to 8. Inactivation of spores under these conditions was maximally 80% and was not increased at low pH. However, higher levels of inactivation were obtained when spores were first pressure treated at neutral pH and then exposed for 1 h to low pH. This large difference in inactivation could be explained by the finding that pressure-induced spore germination, which is known to occur at neutral pH, was inhibited at low pH (< 5). Pressure treatment at low pH made spores more sensitive to heat inactivation, suggesting that demineralized H-spores had been formed. Changes in spore core hydration and pH upon exposure of spores at low pH were studied in a more direct way using green fluorescent protein expressed in recombinant B. subtilis as a reporter protein, and it was confirmed that pressure and heat increase spore permeability for protons. Based on these results, the potential of low temperature, high pressure processes for spore inactivation in acid products is discussed.
将枯草芽孢杆菌孢子悬浮液在40℃、100和600MPa压力下以及pH值3至8的范围内进行压力处理。在这些条件下，孢子的最大失活率为80%，且在低pH值下不会增加。然而，当孢子先在中性pH值下进行压力处理，然后在低pH值下暴露1小时时，可获得更高水平的失活。这种失活的巨大差异可以通过以下发现来解释：已知在中性pH值下发生的压力诱导孢子萌发在低pH值（<5）下受到抑制。低pH值下的压力处理使孢子对热失活更敏感，这表明已形成了脱矿质的H型孢子。使用重组枯草芽孢杆菌中表达的绿色荧光蛋白作为报告蛋白，以更直接的方式研究了孢子在低pH值下暴露时孢子核心水合作用和pH值的变化，并证实压力和热会增加孢子对质子的渗透性。基于这些结果，讨论了低温、高压处理对酸性产品中孢子失活的潜力。
