The Effect Of Freezing Treatment On The Storage Characteristics Of Rice

During rice storage or logistics,freezing and low temperatures may be encountered,but the impact of freezing on rice storage is not fully understood.In this paper,using E’zhong-5 rice as raw material,rice was stored for a short time in a simulated freezing environment,and then storage experiments were carried out to study the effect of freezing on rice quality and the change of quality during the storage process of frozen rice.The main research contents are as follows:The quality analysis of the two water(13.5% and 15.1%)paddies was carried out after storage at 4,-18 and-30°C for 30 days and 60 days,respectively,and the changes of rice quality before and after storage in different environments were compared.The results showed that the germination rate of rice stored in the freezing environment decreased significantly,and the germination rate decreased the fastest when the freezing temperature was-30°C and the moisture content was 15.1%.The activity of peroxidase(POD)in rice showed a downward trend in the freezing environment,and the lower the freezing temperature,the higher the moisture content of rice,and the greater the decrease in activity.The activity of polyphenol oxidase(PPO)in rice showed a downward trend in the freezing environment,and the decrease was large from 0 to 30 days,but there were no significant differences between the groups with different moisture content and different freezing temperature.Under freezing environment,the activity of rice catalase(CAT)showed a trend of first increasing and then decreasing.After storage in the freezing environment,the roughness rate and polished rice rate of rice decreased,the moisture content of rice was 15.1%,the freezing temperature was-18°C,and the polished rice rate decreased the most.The water absorption,expansion and solids of rice showed a downward trend in the freezing environment,and the solids of rice soup with a moisture content of 15.1% decreased the most.In the freezing environment,the peak viscosity and valley viscosity of rice showed a downward trend.In the freezing environment,the fatty acid value of rice showed an upward trend,with the largest increase when the moisture content was 13.5% and the freezing temperature was-30°C.The effects of freezing on the storage characteristics of rice were explored by storing rice with moisture content of 13.5% and low temperature of 4,-18 and-30°C for 30 days for 240 days,and the quality of rice at 20 and 30°C was monitored.The results showed that when stored at 20 and 30°C,the germination ability of frozen rice was lost very quickly,and the activities of CAT,POD,PPO,and α-amylase(AMS)decreased faster than those of unfrozen rice,and the enzyme activity of rice at freezing temperature of-30°C and storage temperature of 30°C decreased the fastest.The freezing process accelerated the decline of polished rice rate and the increase of yellow grain rice rate in rice storage.Frozen rice ends up with a higher viscosity when stored.The water absorption rate and expansion rate of frozen rice increased rapidly,and the decline rate of rice soup solids accelerated.Compared with-18°C freezing,-30°C freezing has a greater impact on the cooking quality of rice after storage.After 240 days of storage,the fatty acid value of rice had the greatest increase in freezing temperature of-30°C and storage temperature of 30°C.After storage,the frozen rice has higher hardness and chewiness,and lower adhesion and elasticity.The volatile components of rice were analyzed by gas chromatography-ion mobility spectrometer,and the effect of freezing treatment on the volatile components of rice after storage was discussed.The results showed that compared with rice without frozen treatment,the concentration of some esters in rice decreased or disappeared after storage at 30°C,while the concentration of some ketones and aldehydes increased.When frozen rice is stored at 20°C,the concentration of some alcohols and esters in the rice becomes lighter.