The Effect Of Rice Yellowing On The Quality Characteristics And Volatile Compounds

The raw materials of this experiment were non-yellowed rice and yellowed rice of Taihu glutinous rice,Jiahua japonica rice,Fengliangyou indica rice,Japonica glutinous rice,Yanfeng 47 japonica rice and Yanfeng series japonica rice.The physical and chemical indicators of non-yellowed rice and yellowed rice were studied by automated seeds and grains analyser,rapid viscosity analyzer(RVA)and the differential scanning calorimetry(DSC).The volatile compounds of non-yellowed rice and yellowed rice were detected by gas chromatography-mass spectrometry(GC-MS),gas chromatography-ion migration spectrometer(GC-IMS)and electronic nose.Samples were observed by rice appearance quality detector.It was found that although rice yellowing was found to have no significant effect on the transparency of glutinous rice,the transparency of japonica rice and indica rice was significantly decreased.The rice yellowing caused a significant increase in the chalkiness of six varieties.The thermodynamic properties of samples were detected by differential scanning calorimetry(DSC).It was found that the effect of rice yellowing on ΔH was not significant.Although the effect of rice yellowing on peak temperature was not significant in Taihu glutinous rice,Fengliangyou indica rice and Yanfeng series japonica rice,it caused a significant increase in the other three varieties.The gelatinization characteristics of six varieties of rice were studied by rapid viscosity analyzer(RVA).It showed that the effect of rice yellowing on the breakdown was not significant in Jiahua japonica rice and Yanfeng series japonica rice,but it caused Taihu glutinous rice,Japonica glutinous rice and Yanfeng 47 japonica rice to decreasse.Although the setback of Taihu glutinous rice,Jiahua Japonica rice and Japonica glutinous rice did not change so much,it increased significantly in Fengliangyou indica rice,Yanfeng 47 Japonica rice and Yanfeng series Japonica rice due to rice yellowing.The volatile compounds of non-yellowed rice and yellowed rice were evaluated by gas chromatography-mass spectrometry(GC-MS)and gas chromatography-ion migration spectrometer(GC-IMS).The volatile compounds detected in all samples were mainly aldehydes,alcohols,ketones,alkanes,esters and heterocyclic compounds,in which the relative contents of aldehydes,alcohols and hydrocarbons accounted for a large proportion of all volatile compounds.Both the GC-MS and GC-IMS results showed that the relative content of aldehydes in yellowed rice was much higher than that in non-yellowed rice.The non-yellowed rice and yellowed rice of Yanfeng series japonica rice were mixed evenly in a certain proportion.The volatile compounds of six different proportions of samples were quickly detected by electronic nose and the data were analyzed by principle component analysis(PCA).It was found that the proportion change of the samples has a certain correlation with the distribution of the sample in the PCA chart.