等温水分活度及其对低水分食品中微生物抗热性的影响研究进展

Water Activity at Isothermal Temperature and Its Effect on Microbial Heat Resistance in Low-moisture Foods

水分活度(Water activity,a_(w))是定义低水分食品(a_(w,25℃)<0.85)的关键指标,对低水分食品(LMFs)中微生物的抗热性起着决定性的作用。食品的水分活度受到食品组分、质构等的影响,并且与温度密切相关,在温度改变时呈现不同的变化趋势,是典型的温度依赖型指标。等温水分活度(a_(w,T))反映了食品在高温灭菌过程中的实时水分活度,其准确测定或推算有助于学者量化低水分食品中微生物抗热性指标,进而设计、验证、完善相关热灭菌工艺。但商业化的水分活度仪只能测量低温区间(20~50℃),人们对高温区间(>55℃)的水分活度还了解甚少。本文首先介绍了低水分食品微生物安全及其抗热性指标,然后对等温水分活度的定义、检测方法、模型预测、影响因素及其对微生物抗热性的影响研究进行综述。等温水分活度的认知与测定有利于食品企业降低低水分食品的微生物污染程度,保障消费者食品安全。

Water activity (a_(w)) is the key factor defining low-moisture foods (LMFs,a_(w,25℃)<0.85),and also determines the heat resistance of microorganisms in LMFs.However,a_(w) of food is a temperature-dependent factor,and is highly influenced by food components and texture.When temperature rises,a_(w) has shown different trends of changes.Water activity at isothermal temperature (a_(w,T)) reflects the real-time a_(w) of foods during high-temperature pasteurization.Accurate measurement and calculation of a_(w,T) enable scholars to quantify the heat resistance parameters of microorganisms in LMFs,and to design,verify,and improve associated thermal pasteurization processes.However,commercial a_(w) meters can only conduct the measurement at low temperature range (20~50℃).Little is known on the a_(w) in the high temperature range(>55℃).The microbial safety of LMFs and its microbial heat resistance parameters are first introduced in this article.Then the definition,detection methods,model predictions,influencing factors of a_(w),T and the effects of a_(w,T) on microbial heat resistance of LMFs are summarized.Recognition and measurement of a_(w,T) are beneficial for food industries to reduce the degree of LMFs microbial contamination and ensure consumers food safety.