Changes In Quality Of High-quality Indica Rice Under Different Storage Conditions

This article mainly studies the quality changes of paddy rice during storage with temperature variations.The high-quality Indica called Yue Nong Si Miao harvested in November 2018 are taken as the research material.The moisture content(13.5%)of the paddy rice were stored for 360 days in glass bottles with 6 kinds of modes in early January 2019.The bottle cap is opened once a week to ensure that there is sufficient air in the bottle for normal breathing of paddy rice.Each storage mode is divided into6 stage,6 kinds of modes are:(1)15-15-15-15-15-15 ℃(15℃ constant temperature),(2)30-30-30-30-30-30-30℃(30℃ constant temperature),(3)15-30-15-30-15-30 ℃,(4)30-15-30-15-30-15℃,(5)15-15-15-30-30-30 ℃,(6)30-30-30-15-15-15 ℃.Each Stored for 60 days in each phase.Every 60 days,physical and chemical indexes(germination rate,enzyme activity,gelatinization characteristics,cooking quality,fatty acid value),volatile components,and microstructure of embryo were detected.The main objectives are to study the differences of the quality changes between the temperature-changing and constant-temperature mode,as well as the temperature-changing and the constant temperatures modes.The results show that:(1)The quality of paddy rice was great influenced by the different storage modes.Comparing these physical and chemical indicators under the six kinds of storage modes,we found that:(1)further verified that long-term low temperature can significantly delay the deterioration of rice quality;(2)Comparing the mode 3 and 4,which were two temperature-changing modes with relatively high frequency of temperature-changing(alternate/60d),founding mode 3(15-30-15-30-15-30 ℃)can delay the deterioration of some physical and chemical indicators of rice in a certain period of time,such as germination rate,enzyme activity,final viscosit,retrogradation value,rice soup p H and water absorption rate.The other indicators have no significant difference with mode 4(30-15-30-15-30-15℃);(3)For the two modes of 5 and 6 with relatively low frequency of temperature-changing(alternate/180d),the temperature-rising mode is not conducive to the later storage of paddy rice,such as physiological activity(germination rate,enzyme activity),final viscosity,and retrogradation value deteriorated faster than the experiencing same temperature conditions but the frequency of temperature changes is relatively high(mode 3),but within a certain time(within 300d),p H soup and solids content of rice paddy were higher than the other four storage modes(except mode 1).The temperature-coolingmode can delay the declining of physiological activity,rice soup p H,and solid content of rice soup to a certain extent during the later storage period.for the final viscosity and rebound value,low temperature in the later period cannot delay the deterioration of the two indicators because the starch structure has greatly changed for the early high temperature.In the two modes,the change trend of fatty acid value was similar in the late stage,so was the water absorption.The new complex range test was performed on the physical and chemical indicators in the experiment,and the results were comprehensively analyzed.The decline degree of the rice quality during storage with the 6 storage modes was sorted from large to small,as follows:Mode 2> Mode 6> Mode 4 > Mode 3> Mode 5>Mode 1.(2)The changes of volatile components during storage were studied.The principal component study found that the composition changes of the main volatile components of brown rice obtained from rice under 6 storage modes were different:(1)Mode 1(15℃constant temperature)is similar to the mode 3(15-30-15-30-15-30℃)in the composition of the main volatile components of brown rice obtained from paddy rice.The first two main components with larger contribution rates are aromatics and alkanes;(2)Both the main components that contribute most to the volatile components of brown rice obtained from rice in mode 5(15-15-15-30-30-30-30℃)and mode 6(30-30-30-15-15-15℃)are esters;the main components of the second and third contribution ratios in mode 6 and mode 4(30-15-30-15-30-15℃)are Olefins and heterocyclic rings;(3)Brown rice obtained from rice under mode 2(30℃constant temperature)has the largest volatile component contribution rate:aldehydes,esters,and olefins;Mode 4 is ketones,olefins,Some studies have shown that when the contribution rate of aldehydes and ketones in volatile components are high,it indicates that the deterioration of rice quality is more serious.(3)The microstructure of the original and paddy rice stored under modes 1,2,3,and 4 for 240 d were studied.we found that the oringal had normal cell morphology and organelle structure,However,the function of accounting,energy and material metabolism in the cells are relatively strong.When the storage reaches 240 days,the order of the internal integrity of the rice germ cells and the structure of the organelles are: Mode 1> Mode 3 > Mode 4> Mode 2,it also reflects the speed of cell aging in the 4 modes.