| In this study,the newly harvested long-grain high-quality late indica rice was stored in artificial climate incubators at low temperature(15℃),quasi-low temperature(20℃)and normal temperature(25℃)for 180 days.After unsealing,the rice was stored in artificial climate incubators at 15 ℃,25 ℃ and 35 ℃ for 180 days,during which sampling was conducted every 20 days.The quality indexes,cooking quality,internal water migration rule,grain structure and mechanical properties of rice were measured during storage.Based on the clear effect of storage temperature on quality of high quality late indica rice,the quality changes of high quality late indica rice under different storage temperatures after the removal of low temperature storage were further studied.In order to provide theoretical basis and guidance for scientific storage of long grain quality late indica rice after low temperature storage and unsealing.The main results of this study are as follows:(1)The quality index,physiological quality and storage quality of rice after being unsealed at low temperature were measured.The results showed that the storage quality index of rice changed with the extension of storage time.The quality of rice stored at 15℃was better than that stored at 25℃ and 35℃.Storage of unsealed rice at lower temperature can delay quality deterioration to a certain extent.The influence of temperature difference before and after unsealing on rice quality was mainly reflected in the early stage of unsealing,and the influence gradually decreased with the extension of storage time.Storage time,temperature and temperature difference have different degrees of correlation with each quality index of rice,storage time is one of the main factors of rice quality change,storage temperature has a limited effect on the quality index of rice,storage temperature has the least effect on each quality index of rice.(2)The cooking,texture and sensory qualities of rice were measured.The results showed that with the extension of storage time,the eating quality of unsealed rice changed to some extent.Water absorption rate and volume expansion rate increased;Rice soup p H drops.The higher the temperature,the more obvious the quality change.The hardness and adhesion of rice decreased.The change of elasticity of rice unsealed at 15℃ and 20℃ was not obvious,while that of rice unsealed at 25 ℃ showed a decreasing trend.The cohesiveness and recovery are on the rise.The change of mastication was not obvious;Rice should be kept at lower temperature after unsealing to delay the decline of texture quality of rice.The quality indexes of rice during storage had strong correlation with the edible quality of rice.The rice unsealed at 15℃ can be stored at 15℃ for 0 ～ 60 days,25℃ for 0 ～ 40 days,35℃ for 0 ～ 20 days,the rice unsealed at 20℃ can be stored at 15℃ for 0 ～ 80 days,25℃ for 0 ～ 80 days,35℃ for 0 ～ 60 days.The rice unsealed at 25℃ can be stored for 0 ～ 80 days at 15℃,0 ～ 80 days at 25℃ and 0 ～ 40 days at 35℃,which is suitable for making rice.(3)The moisture change of rice after low-temperature storage and unsealing was collected.The results showed that with the extension of storage time,the moisture inside the rice changed to a certain extent.The peak time of different inversion peaks of high quality late indica rice with long grain type was relatively stable after unsealing based on low field nuclear magnetic field,but with the increase of storage time,the peak time decreased slightly,and the freedom of rice water quality seed decreased.The adsorbed water of rice is significantly affected by storage temperature after unsealing.The higher the temperature is,the faster the adsorbed water drops.The adsorbed water of rice after unsealing decreases in the later storage period.Peak T22 did not appear after 180 days of storage.Peak T23 rises.(4)The structural and mechanical properties of rice were measured.The results showed that the microstructures and mechanical properties of endosperm changed with the extension of storage time,the starch crystal type did not change,and the crystallinity increased.Most starch grains in indica endosperm have the same size and are closely arranged.After 180 days of storage,cracks appeared in different degrees between starch cells,and there were more cracks and more smooth cross sections under high temperature.After unsealing,the size of rice stored at different temperatures for 0d and 180 d and the change of the three kinds of crushing displacements were not obvious,and the three kinds of crushing forces were greater than those in the early unsealing stage.The compressive force is greater than the shear force and the three-point bending force,and the shear force is greater than the threepoint bending force.The crushing displacement and deformation of compressive force are higher than those of three-point bending force and shear force.After husking,the three kinds of breaking forces of brown rice vary widely.There was a certain correlation between grain crushing force and grain size under shear force.The lower the water content in the grain,the greater the crushing force,the lower the percentage of coarse and milled rice.The higher the amylose content is,the greater the crushing force,the lower the percentage of roughing and milling rice.The longer the storage time of unsealed rice,the more obvious the quality change;Storage at low temperature can prolong the shelf life of rice and is beneficial to the texture of rice.The quality index of rice has strong correlation with that of rice.With the extension of storage time,the water content of rice changes obviously,and the storage temperature has great influence on the adsorbed water.With the extension of storage time,the structural characteristics of rice changed in different degrees,and the crushing force was affected by water content and amylose content,which had a certain correlation with the processing quality of rice. |
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