Research On The Quality Difference Of Cooked Japonica Rice By Electric Rice Cooker And The Cause

The taste quality of cooked japonica rice is closely related to the cooking parameters of electric rice cooker.However,which are the key cooking parameters,and how the cooking parameters effect the quality of cooked japonica rice,were the main problem demanding prompt solution.The present study selected japonica rice as the research object,conducting a comparative analysis of the differences between taste quality of cooked rice with eight typical heating curves.Partial least squares regression was adopted to figure out crucial flavor compounds influencing the odor characteristic of cooked japonica rice.The crucial physical and chemical indexes influencing the palatability of cooked japonica rice were also pointed out.The key cooking parameters were also confirmed.At the same time,this research further revealed the effect of the key cooking parameters from the point of water migration in the japonica rice kernel and change of starch structure during the cooking process.This research could provide guidance for the improvement of taste quality of japonica rice cooked by rice cooker.In this study,the sensory score,odor characteristic,texture properties and cooking characteristics were used as indexes to evaluate the quality of cooked japonica rice with different cooking parameters.It was found that the quality of the rice cooked by different cooking parameters was quite different.Therefore,the taste quality of cooked japonica rice could be improved significantly by controlling the cooking parameters.The correlation between odor characteristics and odor sensory quality were analyzed by partial least squares regression.The correlation between texture properties,cooking characteristics and sensory quality were analyzed by the same method.The results showed that hexanal,octanal,2-heptenal,furfural,benzaldehyde,geranyl acetone,2-pentylfuran and 2-acetyl-pyrroline were crucial flavor compounds for evaluating odor in sensory.The hardness and elasticity of texture properties,iodine blue value and gelatinization degree in cooking characteristics were the crucial indicators which are related with palatability in sensory.The changes of the crucial flavor compounds during the cooking process were investigated using GC-MS.It was found that the content of most of the crucial flavor compounds increased at the initial of boiling stage,and decreased gradually during cooking.The contents of the crucial flavor compounds inside the condensed water were also analyzed.The results showed that lots of flavor compounds dissolved in the condensed water,and the odor characteristic could be improved obviously by adjusting the temperature at the lid.The effect of cooking parameters on the crucial physical and chemical indexes was analyzed by partial least squares regression.The results showed that the temperature at the water absorption stage had a significant positive correlation with the gelatinization degree,and had an obvious negative correlation with the others.The results of the duration of the boiling stage was the opposite.It was found that higher temperature of water absorption and shorter boiling time was beneficial to the association of water and rice grain matrix,thus improving the palatability of cooked japonica rice such as stickiness,elasticity and so on.The effect of the key cooking parameters on the migration and distribution of water in the japonica rice kernel during the cooking process was further investigated with the use of low field nuclear magnetic resonance.Meanwhile,the change of the crystallinity of japonica rice starch was also analyzed.The results showed that higher temperature and longer time of water absorption,were beneficial to the uniform distribution of water in the rice kernel.In this condition,the degree of gelatinization starch was improved,the hardness of the cooked rice was reduced,and thus the palatability of cooked japonica rice was improved.In addition,the crystallinity of japonica rice starch changed continuously during the heating process,and it dropped quickly when the temperature was above the gelatinization temperature of rice starch.And higher temperature of water absorption would also accelerate the destruction of crystal structure.The effect of cooking parameters in water absorption stage on palatability of cooked japonica rice was analyzed by single-factor experiment,with the use of prototype.The results showed that 20? is the optimal temperature and 50 min is the optimal time of water absorption stage,which was helpful to beneficial to the association of water and rice grain matrix,thus improving the palatability of cooked japonica rice such as stickiness,elasticity and so on.