| The southwest agricultural university paddy research room provided gathering in the crops the extensive (long-grained nonglutinous rices ) of the Ming Hui-63 of paddy to be used as the experimental material, and adopting the method of man-made ageing on this article. The change characteristics of the important nutrients, such as fat, restricted amino acid( lysine and tryptophan) and vitamin B1 and B2, which were easy to occurring the change in the paddy storage course were studied from the dynamics angle.The results showed that under the temperature for 8-15 of paddy storing, lipase activity was unclear change along with storing time lengthening. Extracted lipase activity was strong, approaching the contrast enzyme activity (6.43U).Explaining that the lipase was not destroyed. Along with the increase storing time, the lipase activity assumed monotonous descent to trend when the temperature moving upward to 30癈. The lipase activity descended about 85%, and that the lipase lost basically lives when paddy stored near 5 months in 45 . Explaining that lipase activity was stable basically in shorter time ( 10d ) under 30 - 40 . However, along with the increase of storing time, remnants' activity of lipase constantly reduced, and it was higher to store the temperature, and the speed that the enzyme activity reduced was quicker. This probably was due to the lipase as one kind of living things catalyst, and long time stores to lead to its enzyme protein heat denaturation partly( Li Jianghua 1992 ) under the higher temperature.When paddy storing the temperature to serve as 8 , and it along with storing time lengthens, the free fatty acid content had hardly the change. Changing the temperature for 15 , the free fatty acid content slowly increased. The free fatty acid contentclearly enlarged when the storing temperature moving upward to 30 ,and the temperature was higher, and it was quicker to increase speed. Free fatty acid in the paddy was produced by lipase hydrolysising fat. From the pure enzyme chemical reaction, the lipase activity was higher, and free fatty acid content was higher. But the paddy under the different storing temperature, its lipase activity was reduced along with stores time increased. And at the same time, the free fatty acid content increased following to the increase storing time. Therefore, it was improper that explaining the change trend of free fatty acid content only with the change relation of lipase activity with storing time.The change relation of lipase activity with storing temperature was studied. The results showed that the lipase relative activity increased firstly and then decreased along with the temperature lengthens. At 8 low temperature, the lipase activity in paddy was almost unchangeable after stored closely 5 months, and it was also very low equally to serve as 5.26%.This could be explained by lipase activity being restrained under low temperature. Storing after the 120d under 45 , lipase relative activity was only about 2%, so the lipase lost work basically. Under the temperature for 30-37 , the lipase relative activity could got to the highest along with the time lengthens. Comparing the increase rate of free fatty acid with the change trend of lipase relative activity, both had notable related nature. The result showed that the speed of growth of fatty acid content became being mutually related with oppositeeing to each other lipase relative activity, and the correlation coefficient was: r=0.927,n=7; notable nature standard was smaller than 0.01. The mutually related nature was served as highly notably. It might be fail-safe that we would regard the fully speed of growth of free fatty acid content as the sensitive quota that the quality of paddy was gone bad during the period of paddy storage.The results also showed that the paddy lysine content and tryptophan content reduced gradually when it was stored under the temperature at the difference, and what it was along with storing time lengthens. The higher temperature was, the faster lysine content and t... |
