Quality Changes Of Brown Rice During Processing And Storage

This paper studied the effects of moisture content and husking times on the roughness ratio of rice.On this basis,atomic absorption spectrometry,atomic fluorescence spectrometry,gas phase chromatography,and microbial analysis method were used to determine and analyze the heavy metal content,pesticide residue biomass and microbial growth of rice and brown rice.At the same time,the quality changes of brown rice with different moisture content stored under different temperature conditions were studied.Brown rice samples with different moisture content(13.5%,16%,18%,respectively)were stored at temperature of 4 ℃,16 ℃ and 30 ℃,respectively to simulate the conventional storing conditions,the physiological activity indexes(germination rate,electrical conductivity and malondialdehyde content),chemical indexes(moisture content,fatty acid value),and edible quality indexes(color and texture)were collected according to the methods of GB and related reports.The changes of quality characteristics of brown rice under different conditions were investigated and the correlation between the quality changes of brown rice samples was also discussed.This paper would provide more information of brown rice qualities during storage,which would facilitate the detection personnel obtaining the quality information directly from those several biochemical indexes in brown rice samples.The results showed that the quality changes in rice before and after hulling showed that the bulk density of brown rice significantly increased 30% ~ 40% after hulling.The number of microorganisms decreased,but there was no significant correlation between the decrease and the roughness of rice.Pesticide residue(for example Dimethoate)decreased apparently;however,the changes in chlorpyrifos residues were more complex.Chlorpyrifos residues in most samples in the experiment group decreased after the hulling,but chlorpyrifos residues in several groups did not decreased,but increased,and there was no correlation between chlorpyrifos residues and the roughness.Changes in heavy metal content had no clear rules,and there was no significant correlation between the heavy metal content and the roughness rice.And the quality changes of brown rice samples with different storage conditions were significantly different during the 3-month period.1.Germination rate dropped significantly,especially the high temperature and high humidity group.It’s germination rate has dropped to 51.7% after 21 days;2.Moisture content decreased,but with volatility;3.Conductivity and fatty acid value were affected significantly by water and temperature(P<0.01),more the moisture content and higher the temperature,more rapidly the conductivity and fatty acid value increased;4.MDA content was affected by temperature significantly,higher the temperature,faster the MDA content increased,but was little influenced by water;5.The hardness and adhesiveness of brown rice were changed by temperature and moisture content,more the moisture content and higher the temperature,more rapidly the hardness increased and the adhesion reduced;6.Color difference were in different degrees,too.Conclusion: Hulling will affect the physical and chemical indicators of paddy rie,especially for the microbial indicators.Therefore,this study has great practical significance for change the traditional rice storing pattern to brown rice storing pattern.The qualities of brown rice samples stored under different conditions significantly changed with the store time,and low temperature and low water condition were the key factors to ensure the storage quality of brown rice.The physiological and chemical characteristics are generally consistent with the edible qualities of brown rice,especially MDA value.This paper provides great reference value in obtaining their quality information.