| Three varieties wheat seeds of different hardness were tempered in different ways in this study. The effects of different tempering conditions on wheat tempering process moisture conduction and diffusion were studied by nuclear magnetic resonance. Moisture distribution and seepage path were studied by MRI in tempering process, tempering results of tempering way were analysed and compared comprehensively.The results were as follow:1.T21, A21, T23 were had a significant upward trend when temperature increased in conventional tempering way. T22, A22 were presented a trend of faling before raising, A23 of hard wheat had a downtrend. There existed a siginficant postive correlation between T21, T22,A21, A22 and water addition. However, A23, T23 final steady-state value with the water content had no significant correlation.2. MRI indicated moisture transmission path in conventional tempering way was: Firstly,water went through the nucellus layer into the embryo and spread to pastel side. Secondly,water went through the aleurone layer cell wall outside-in infiltration. And moisture spreaded from the fuzzy gradually to the center of endosperm as auxiliary route way. Study of single grain characteristics indicated that three kinds of wheat hardness had significant changes in conventional tempering. Moreover, the rate of changes on wheat hardness index and the original hardness showed a negative correlation. The grain weight, moisture content, wheat grain diameter were presented a trend of raising before faling. And wheat grain diameter had no significant differences across tempering process. There existed a negative correlation between wheat hardness, grain size and combined water content. The effects of middle water on each index was non-significant.3.T21, T22, A21, A23 had significantly negative correlation with peeling rate. However, T23,A22 had no significant correlation with peeling rate gradient. T21, A21, T23, A23 had positively correlation with tempering temperature, T22 had a positive correlation with tempering temperature when the temperature was 20-30℃. There was no significant correlation between temperature gradient and A22. The best tempering condition was when peeling rate was 6%and the tempering temperature was 30℃. Study of peeling tempering by MRI experiment indicate that water soaked into the aleurone and embryo after endosperm tissue. While water spreaded from the embryo into cotyledon and ruffle cell layer. Besides, it had a higher penetration rate compared with the conventional way.4.There were a positive correlation between T21, T23, T22, A23 and tempering temperature.However, A21 had a opposite correlation. A22 was significantly affected by the wheat varietiesdiversity. T21, T22,T23 had higher value compared with the conventional way. There were a positive correlation between T21, T23, A21 and water addition. The change rate of T22 presented a trend of increased when water addition was 16.5% to 19.5%. With the increase in tempering time, A22 and A23 had a trend of raising before faling.5.Peeling tempering improved flour extraction rate and reduced ash content. Besides the whitness showed no significant difference in conventional and high temperature tempering.But it was higher than peeling tempering. L * and b * had no significant correlation with temperature in peeling tempering. L* and a* had a positive correlation with moisture in conventional and high temperature tempering. There were a negative correlation between protein content, wet gluten, dry gluten content, gluten index and tempering moisture. The protein contents, gluten index of peeling tempering were between the conventional and high temperature tempering. The tempering way had adistinct influence on the contents of damaged starch, falling numbers and pasting properties.6.The tempeing effects of three tempering way were analysed comprehensivly. The result was as follow: the best tempering condition was wheat peeling rate as 6% and temperature as30 ℃. |
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