Effect Of Storage Condition On Rice Quality

It would be decreased of paddy quality in the process of be stored, it was called ageing, with the storage time longer, the quality of paddy worse. Storage environment would affect the ageing speed, the research studied the relationship between paddy quality and environment factors like as temperature, relative humidity and storage time. The change of germination rate, milling quality, fatty acid and -SH content, phenolics, cooking quality and the rate of starch digestion during different storage conditions. The results were made as follows:With the storage time longer, paddy germination rate lower, brown rice recovery was no law to follow, head yield a downward trend. With rising temperature and increasing relative humidity, the change was more obvious. Paddy germination and head yield were influenced by temperature, relative humidity and storage time, the effect order was as follow:storage time> storage temperature> relative humidity, the difference of head yield was significantly while storage time changed (P<005).The main fatty acid in paddy were octadecadienoic acid, C18:1,11 and octadecenoic acid, there were a little of C16:、C18:0、C18:1,9. With prolonging the storage time, the relative content of octadecadienoic acid and C18:1,11 had a upward trend, the effect was more remarkable under higher temperature and relative humidity, but the relative content of octadecadienoic acid was increasing more than C18:1,11. The relative content of octadecenoic acid reduced because of oxidation, higher temperature and relative humidity reduced quickly. Orthogonal analysis showed that storage time played the most important role in effecting the relative content of octadecenoic acid, and the difference of the relative content of octadecenoic acid was significantly while temperature changed. With increasing storage time,-SH content decreased, under effected by temperature and relative humidity together, the effect was more remarkable.The main phenolics in paddy were p-coumaric acid and ferulic acid. With prolonging the storage time, the content of free phenolics was no law to follow. With increasing storage temperature, free phenolics had an upward trend in whole, there was a relationship between the content of free phenolics and relative humidity, the content of free phenolics raised with increasing relative humidity in the ranger of RH55%-85%, but there were some variable in different temperature. The content of bound phenolics decreased with the storage processing. With rising temperature and increasing relative humidity, the content of bound phenolics reduced, and the effect was more remarkable with higher temperature and relative humidity. The content of free p-coumaric acid increased with prolonging storage time, rising temperature and increasing relative humidity, but the change was not obvious. With storage time longer, the content of bound p-coumaric acid decreased, and the temperature and relative humidity played the same role in the content of bound p-coumaric acid. The content of free ferulic acid rised with prolonging storage time, rising temperature and increasing relative humidity, the content of bound ferulic acid reduced with prolonging storage time, rising temperature and increasing relative humidity. Orthogonal analysis showed that in the storage process, storage time was the main effect factor on the change of content of bound p-coumaric acid and bound ferulic acid, the difference of content of bound p-coumaric was significant while storage time changed(P<0.05).orage temperature was the main effect factor on the change of content of bound phenolics, and the impact by temperature was remarkable (P<005).Rice water absorption ratio increased in the storage process, and the temperature rised, the change was more obvious. With increasing relative humidity, rice water absorption ratio had an upward trend, but the uptrend between rice water absorption ratio and relative humidity was different as temperature changed. Orthogonal analysis showed that relative humidity played the most important role in effecting the rice water absorption ratio, temperature was the second factor, time was the last factor, but the impact of three factors was not remarkable. In the storage process, there was no significant correlation between rice expansion ratio and storage time, rice expansion ratio had an upward trend with increasing temperature, with increasing relative humidity, rice expansion ratio rised, especially relative humidity over 65%. With prolonging storage time and rising temperature, pH value of residual cooking water lower, there was no relationship between relative humidity and pH value of residual cooking water. With storage processing, there was a relationship between iodine-blue value of residual cooking water and storage time, storage time longer, iodine-blue value of residual cooking water lower, and the change was more obvious under effected by temperature and relative humidity together because of the content decline of amylose influenced by higher temperature and relative humidity, rice eating quality was deterioration.With prolonging storage time, the rate of starch digestion declined. There was small impact on the rate of starch digestion when the temperature and relative humidity were low, and with rising temperature and increasing relative humidity, the rate of starch digestion decreased. Orthogonal analysis showed the rate of starch digestion was influenced by that storage time, storage temperature, relative humidity, but it played different role, the effect order was as follow:storage temperature> storage time> relative humidity, the difference of the rate of starch digestion was significantly while storage temperature changed (P<005).