Instituto de Biotecnología Vegetal, Edificio I+D+I, Muralla del Mar, 30202, Cartagena, Murcia, Spain.
Int J Food Microbiol. 2012 Aug 1;158(1):36-41. doi: 10.1016/j.ijfoodmicro.2012.06.017. Epub 2012 Jul 2.
Bacillus weihenstephanensis is a psychrotolerant bacterium belonging to the Bacillus cereus group. Some strains may be cytotoxic although they have not been described as food-poisoning agents so far. The objective of this work is to model the effects of temperature and a(w) downshifts on the lag time of B. weihenstephanensis and the dependence of μ(max) on the growth conditions (temperature and a(w)). Effects of temperature downshifts were studied on 30 experimental conditions (shifts magnitude ranging from 2 to 20 °C, temperature after shift from 10 to 20 °C and a(w) ranging from 0.977 to 0.997). Osmotic shifts were studied for 13 conditions (shift magnitude ranging from 0.008 to 0.020 units of a(w), temperature from 10 to 30 °C, a(w) after shift from 0.977 to 0.997). Experimental results show that temperature downshifts were able to induce considerable lag times (up to 20 days) when occurring near the growth limits. At lower temperatures, osmotic shifts had also a significant effect. Validation experiments in food subjected to changing conditions of temperature showed that the model provided valid predictions in diluted creamed pasta but overestimated bacterial growth in carrot soup (fail safe predictions).
解淀粉芽孢杆菌是一种耐冷细菌，属于蜡样芽孢杆菌群。虽然有些菌株可能具有细胞毒性，但迄今为止尚未被描述为食源性中毒剂。本研究的目的是模拟温度和水分活度下降对解淀粉芽孢杆菌的滞后时间的影响，以及μ(max)对生长条件（温度和水分活度）的依赖性。研究了 30 种实验条件下的温度下降影响（下降幅度从 2°C 到 20°C，下降后温度从 10°C 到 20°C，水分活度从 0.977 到 0.997）。研究了 13 种渗透变化条件下的渗透压变化（渗透压变化幅度从 0.008 到 0.020 个水分活度单位，温度从 10°C 到 30°C，渗透压变化后水分活度从 0.977 到 0.997）。实验结果表明，当温度下降接近生长极限时，能够诱导相当长的滞后时间（长达 20 天）。在较低温度下，渗透压变化也有显著影响。在经历温度变化条件的食品中的验证实验表明，该模型在稀释奶油意大利面中提供了有效的预测，但高估了胡萝卜汤中细菌的生长（失效安全预测）。
