Water activity change at elevated temperatures and thermal resistance of Salm...

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Water activity change at elevated temperatures and thermal resistance of Salmonella in all purpose wheat flour and peanut butter
万能面粉和花生酱中的水分活度变化及沙门氏菌的耐热性

     Water activity (aw) is a major factor affecting pathogen heat resistance in low-moisture foods. However, there is a lack of data for aw at elevated temperatures that occur during actual thermal processing conditions, and its influence on thermal tolerance of pathogens. The objective of this studywas to gain an in-depth understanding of the relationship between temperature-induced changes in aw and thermal resistance of Salmonella in all purpose flour and peanut butter at elevated temperatures (80 oC). Equilibrium water sorption isotherms (water content vs. water activity) for all purpose wheat flour and peanut butter over the range of 20 to 80 °C were generated using a vapor sorption analyzer and a newly developed thermal cell. The thermal resistance (D80-values) of Salmonella in all purpose wheat flour and peanut butter with initial aw of 0.45 (measured at room temperature,  ~20 °C) was determined via isothermal treatment of small (b1 g) samples.When increasing sample temperature from20 to 80 °C in sealed cells, the aw of all purpose flour increased from 0.45 to 0.80, but the aw of peanut butter decreased from 0.45 to 0.04. The corresponding estimated D80-values of Salmonella in all purpose flour and peanut butter with 20 oC aw of 0.45were 6.9±0.7 min and 17.0±0.9 min, respectively. The significantly (P b 0.05) higher D80-value of Salmonella in peanut butter than in all purpose flour may be partially attributed to the reduced aw in peanut butter in comparison to the increased aw in all purpose flour at 80 °C. The improved understanding of temperature-induced changes in aw of low-moisture products of different composition provides a new insight into seemly unpredictable results, when using heat treatments to control Salmonella in such food systems.

      水分活度(Water活度，aw)是影响病原耐热性的主要因素。然而，对于在实际的热处理条件下发生的高温aw，以及其对病原体热耐受性的影响，缺乏数据。本研究的目的是深入了解高温(80℃)下，由温度引起的aw变化和万能面粉和花生酱中沙门氏菌的耐热性之间的关系。所有用途的小麦面粉和花生酱的平衡吸水等温线(水分含量与水活度)在20 - 80℃范围内使用蒸汽吸附分析仪和新开发的热电池产生。对小样品(b1 g)进行等温处理，测定了初测aw为0.45的通用小麦粉和花生酱中沙门氏菌的热阻(d80 -值)。在封闭的细胞中，当样品温度从20℃提高到80℃时，所有目的粉的aw从0.45提高到0.80，而花生酱的aw从0.45降低到0.04。20℃aw为0.45时，普通面粉和花生酱中沙门氏菌的d80估计值分别为6.9 0.7 min和17.0 0.9 min。显著(P b 0.05)高D80-value花生酱沙门氏菌的比中筋面粉可以部分归因于减少在花生酱相比增加了aw aw中筋面粉80 c .改进的理解温度引起的变化在aw不同成分的低湿度产品提供了一个新的见解有礼的不可预知的结果,当使用热处理控制沙门氏菌的食物系统。

Keywords:Low-moisture foods；Water activity；Decimal reduction time；Salmonella；Water sorption isotherm；All purpose flour；Peanut butter


关键词:低湿度的食物；水活动；十进制时间减少；沙门氏菌；水吸附等温线；中筋面粉；花生酱