The Changes Of Rice Quality Under Different Environmental Conditions After Low Temperature Storage

In order to study the changes of rice’s quality after low temperature storage, selectingnortheast non-glutinous rice as experiment materials, and using two kinds of climateconditions in China, conditional simulation storage settings were35℃and80%RH,30℃and70%RH, and with the climatic conditions in Zhengzhou as a control. Regularly textinganalysis of rice quality, such as the appearance of the sample characteristics, physical andchemical index, microorganism activity index, the rice cooking quality, structure index. Andanalysis physical and chemical index correlation, combining with the valuator value change;screening influence rice quality uses the grey correlation analysis method in order to changethe sensitivity of indicators. The primary conclusions are as follows:(1) At35℃,80%RH environment, and30℃,75%RH environment the moisture contentreach balance trend in the end.But stored at room temperature environment, rice water contentdecreased sharply. With the extension of storage time, the more serious the rice rancid odor,surface color darkening, gloss disappear. Three conditions, along with the storage timeprolonging, rice brightness L*showed a downward trend, b*rice was gradually increasedtrend, rice a*was negative and decreased during the storage time.(2) The storage time of rice and rice dry matter and pH value was significantly negativelyrelated substances, significantly positive correlation with the volume and rice waterabsorption and expansion of rice. Storage time and steamed rice flexibility, adhesiveness wassignificantly negatively correlated with steamed rice, the hardness, gumminess, chewinessshowed significant positive correlation. Steamed rice taste value and storage time of rice, rice,water absorption rate, pH value and volume expansion of rice rice dry matter wassignificantly correlated, steamed rice taste value and hardness, gumminess, resilience,cohesiveness was significant correlation, and chewiness were significantly correlated withcohesion. Show close hardness, gumminess, flexibility, adhesion between rice cooking andtexture characteristics of steamed rice. And steamed rice taste value and rice dry matter thecorrelation coefficient was the highest, reaching0.953.(3)Along with the storage time prolonging, the activity of polyphenoloxidase and theperoxidase activity and the amylase activity were decreased; the fatty acid value, conductivityand microbial activity gradually increased; MDA content of rice increased at first, thendecreased. Storage time and fatty acid value, the landing was significantly positively related to numerical, MDA content and microbial activity, and significantly negatively correlatedwith the activity of polyphenoloxidase and peroxidase activity. Steamed rice taste value wassignificantly correlated with the fatty acid value, falling number, MDA content, electricalconductivity and water, showed a significant correlation between rice cooking quality andphysicochemical index.(4) In the aging process of milled rice with the rice cooking and eating value influence is mostsensitive indicators are: the fatty acid (X3), L*value (X6), falling number (X4),malondialdehyde (X5). Establishment of regression mathematical model: Y=138.28-0.310*-4.79*-0.11*falling number of fatty acid. With the first order kinetic model can be indicatorsof quality changes during storage was rice’s, and according to the rice the first order kineticmodel can predict the rice is very good quality, through the validation of the model is reliable.