| Glutinous rice is one of the most popular traditional staples in China.It is a staple food in many festivals,while frozen glutinous rice balls are the second most sold frozen food in China.Both are made from glutinous rice.Japonica glutinous rice is mainly grown in northern China.Before it is processed into products,it usually goes through a period of storage during which its quality changes.In this study,three typical japonica glutinous rice products and main varieties representing China’s three major rice varieties were used as raw materials to study their quality changes under different storage conditions,objectively evaluate the use of japonica glutinous rice with different storage periods,and define the optimal storage period and quality change range of raw materials for glutinous rice and frozen glutinous rice balls.(1)In order to investigate the change of raw material quality characteristics of japonica glutinous rice during storage,the physical and chemical properties,gelatinization quality,microstructure and crystal structure of rice were measured by artificial storage method,and their change rules were analyzed.With the prolonging of storage time,the overall trend of a *value,b * value,fatty acid value,malondialdehyde and electrical conductivity of japonica glutinous rice increases.L* value,germination rate,peroxidase and gel consistency decreased,and the higher the temperature,the more significant the changes were.After stored rice,more starch particles were exposed,and the crystallinity increased.The higher the temperature,the greater the influence,and the starch crystal form did not change.The correlation analysis showed that except amylose,the quality indexes of japonica glutinous rice were strongly correlated,and the changes of quality were closely related.(2)In order to study the variation rule of gelatinization characteristics of japonica glutinous rice during storage,and explore its storage characteristics.The gelatinization characteristics of rice were measured by rapid viscometer.With the increase of storage time,the peak viscosity,minimum viscosity,disintegration value,final viscosity and recovery value of japonica glutinous rice all show a significant upward trend.The higher the temperature is,the more obvious the change trend is,while the peak time and gelatinization temperature wave have no obvious changes.Correlation analysis showed that the storage time had a great influence on the storage quality of rice,except for amylose,the quality index of japonica glutinous rice significantly affected its gelatinization characteristics.In addition to the gelatinization temperature,there is a significant correlation between the raw material quality and gelatinization characteristics of japonica glutinous rice samples.Therefore,the gelatinization quality of rice can be predicted by its raw material quality.(3)In order to understand the adaptability of glutinous rice processing from japonica glutinous rice at different storage stages,glutinous rice was processed and its cooking,texture and sensory quality were measured.The quality of glutinous rice was comprehensively evaluated by using correlation,principal components and cluster analysis,and the adaptability of glutinous rice was discussed.The best storage period and the range of raw material quality of the Japonica glutinous rice suitable for glutinous rice processing were determined.The results showed that with the extension of storage time,the hardness of glutinous rice firstly increased and then decreased,the cohesion,masticability and resilience increased,and the elasticity and adhesion decreased.The higher the temperature,the more significant the change was.The quasi-low temperature storage was more conducive to the maintenance of texture and quality of rice,and the shorter the storage time,the better the quality.The physicochemical and gelatinization properties of japonica glutinous rice are strongly correlated with the hardness,cohesion,chewability and resilience of rice,and are also strongly correlated with cooking and sensory quality,indicating that the physicochemical and gelatinization properties of raw materials have a great influence on the edible quality.During the whole storage period,the comprehensive score of japonica glutinous rice was the highest,and the score decreased with the extension of storage time.In the cluster analysis,the Japonica glutinous rice classified as the first category has the best comprehensive quality and is suitable for making glutinous rice,including the glutinous rice made from 0 d,60 d,120 d,180 d and 240 d rice stored at 20℃ and room temperature.The raw material quality of this kind of rice is similar to that of glutinous rice.It has lower b* value(11.49 ～ 12.43),lower fatty acid value(25.51 ～ 39.53 mg/100g),higher gel consistency(103 ～ 120 mm)and moderate peak viscosity(2747 ～ 2887 c P),moderate hardness(1201-1315 g),moderate chewiness(171.5 ～ 194.8 g),and high dry matter of rice soup.(7.29 ～ 10.33%).(4)to understand the adaptability of different storage period of japonica rice processing quick-frozen dumplings,to processing quick-frozen dumplings,rice and cooking,quality and structure,and sensory quality were measured,using the correlation,principal component and cluster analysis on comprehensive evaluation of the quality of quick-frozen dumplings,clear appropriate processing quick-frozen dumplings japonica best of waxy rice storage period,and the quality of the raw material.The results showed that with the prolongation of storage time,the color of glutinous rice flour became dark and yellow,the solubility and swelling power decreased,the water separation rate increased,the paste rate increased,and the water absorption rate of glutinous rice flour did not change significantly.The hardness,chewability and resilience of Tangyuan increased,the adhesion first decreased and then tended to be stable,but the elasticity and cohesion of Tangyuan did not change significantly.After a certain period of storage,the sensory scores such as hardness,masticability,color,elasticity and viscosity of the prepared Tangyuan have been improved to varying degrees,and the eating scores have also been improved.The correlation analysis showed that the physicochemical and gelatinization properties of rice had a strong correlation with the quality of glutinous rice flour and glutinous rice balls.The physicochemical properties of rice are strongly correlated with the color,smell and taste,and the gelatinization properties are strongly correlated with the sensory quality of the dumpling,so the quality of the dumpling can be predicted by the physicochemical and gelatinization properties of the raw materials.Principal component analysis showed that the composite score of Tangyuan at 20℃ and room temperature gradually increased with time,while the composite score at high temperature first increased and then decreased.Cluster analysis showed that the quick-frozen dumplings made from rice stored at 20℃ for 180 ～ 360 d and at room temperature for 120 ～ 360 d had the best comprehensive quality.The rice stored at 35℃ffor 60 ～ 180 d in Wan Kennuo 2 and Zhennuo19 and the rice stored at 60 ～ 240 d in Longjing 57 also had higher comprehensive score.The raw material quality of this kind of rice and the quality characteristics of Tangyuan are close to each other.It has low b*(2.50 ～ 3.56),low amylose content(2.0 ～ 2.7%),high gel consistency(98 ～ 121 mm),moderate peak viscosity(3069 ～ 3428 c P),moderate hardness(395 ～ 498 g)and moderate chewiness(218 ～ 248 g),moderate solubility(4.97 ～ 9.78%)and low water separation rate(1.01 ～ 5.6%). |
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