The Effect Of Temperature Fluctuation On Stored-Wheat Safe Moisture Content And Microbial Activity

In this paper, we made an intensive study on the factors that may have influences on the growth and reproduction of mold during the storage process of wheat, those factors including the speed of temperature variation, the particular pattern of temperature change and moisture. At first time, we confirmed the safety moisture and storied period of wheat with different water content under changed temperature; also the activity of mold was studied. Those findings provide a better scientific reference than routine analogy by experience for wheat storage and food safety control thus may have a promising application prospect.Consider the facts that the temperature of grain may be influenced by air temperature, So we analysised the temperature changing properties of granary.The results indicated that the surface temperature is the most susceptible to air temperature and the temperature change of granary is lagging behind the air temperature, the farther the distance, the more obvious the trends is. On the basis of the thories, choosing four rates of temperature change(1d/℃、2d/℃、3d/℃、4d/℃), two changes of temperature model--the heating and cooling, temperature range from10℃to35℃,six kinds of water content of wheat(13.0%、13.5%、14.0%、14.5%、15.0%、15.5%). The significant experimental data were analysised using SPSS software, and the safe moisture and mold activity pattern during wheat storage periods were studied.The temperature change rate and pattern are important factors that can affect the safe moisture of grain. Under the same temperature range, the safe moisture of grain in heating mode is higher than in the cooling mode to0.5%, besides, the faster the temperature changes, the more obvious the difference is. Under the same temperature range and the same model, when the period of the temperature changes1℃increased by1d, the safe moisture content decreased by0.5%. The mildew under the cooling model is happened easily than the heating model, the mildew period differs by21d mostly.When water content, initial temperature of wheat under two kinds of different rates of temperature patterns are the same, the safe storage time of different rates of temperature patterns showed some differences. During the hating process, when the period of the temperature changes1℃increased by1d, the safe storage period decreased7d at most, the time of mildew occurrence earlier by14d at most. While during cooling process, when the period of the temperature changes1℃increased by1d, the safe storage period decreased by21d at most. When The temperature change rate and temperature pattern are the same, the initial temperature is lower by5℃, safe moisture content increased by1%at most, wheat mildew starting time increased by7d at most. Under2d/℃storage process, the initial temperature is lowered by5℃lower, safe moisture of wheat increased by1%, mildew start time increased by7d; under3d/℃storage process, the initial temperature is lowered by5℃, safe moisture content of wheat increased by0.5%at most, mildew starting time up to7d at most.The theroy of the small simulation granary and the small scale simulation are similar. Under the similar storage conditions, the mildew of the small scale trial is easier than the small granary, the period of small scale trial began to mildew up to35d at most, or the small granary is safe; The small-scale test is safe, so is the small barn.