Study On Water Activity Used In Food Microbial Safety Inspection And Control Of Escherichia Coli

International Standardization Organization (ISO) and Association of Official Analytical Chemists-Food and Drug Administration (AOAC-FDA) have brought water activity as an index into many criteria related with food quality and safety inspection control and Hazard Analysis Critical Control Point.There is a serious insufficient of applications, research and standards establishment about water activity related to food safety in China. In this study, the influence mechanisms of water activity on food quality were introduced. Research progresses are reviewed about its application in food industry, control in quality and safety inspection, water activity detection methods and related standards at home and abroad. The relationship between water activity index and the microbial health indicators is proclaimed, using the model to establish a kind of fast and convenient testing method of controlling the water activity by controlling microorganisms indirectly. The main research subjects and results are listed as follows:1. Measuring the water activity of and moisture sorption isotherm different foods. It is verified that dynamic dewpoint isotherm instrumental measurement method could be used to measure the water activity of food and moisture sorption isotherm and to get accurater results.2. Taking four typical food samples for exsampls, the growth conditions of Escherichia coli in different water activities in four kinds of food samples are monitored, and the phenomena is explored.3. The growth of Escherichia coli in the bread sample was monitored under the same water activity condition to get the growth curve, and the growth mathematical model of Escherichia coli which includes the index of water activity was established. Moreover, the experimental results and data fitting showed that the correlation between the growth coefficient in exponential phase of Escherichia coli and water activity was in a linear relationship. The quality index of water activity about Escherichia coli in the food matrix of sliced breads is calculated as0.93. Moisture absorption isotherm of bread was also determined, and the difference and contact between water activity and moisture content as quality control index to control microorganism was analyzed.