Study Of Lipid Changes In High Quality Indica Rice Under Different Storage Conditions

The quality of rice grain changes continuously during storage,and changes in storage environment and internal chemical components of rice grain can lead to deterioration of rice grain quality,among which lipid is the fastest changing component in rice grain.Therefore,studying lipid changes in rice grain under different storage conditions can help to clarify the mechanism of rice grain aging,so as to optimize the storage conditions of rice grain and slow down the deterioration of rice grain quality.In this experiment,the initial moisture content of paddy was adjusted to 13.5%,14.5%,and 15.5%,and stored at different storage temperatures(15℃,20℃,25℃,and 30℃)for 360 d.The changes of lipid physical and chemical indexes,fatty acid fractions,edible quality,and microorganisms were measured periodically to analyze the relationship between rice aging and lipids.In order to investigate the changes of lipid quality after the rice grain was infected by grain storage pests,the experiment selected the moth-eating pest corn weevil to attack the rice grain for 4 weeks,set different population densities(0/500 g,5/500 g,15/500 g)and attack temperatures(20℃,25℃,30℃),and regularly(1 week)measured the changes of lipid quality indexes.The main results were as follows:(1)The changes of lipid indexes of rice grains under different storage conditions were studied.With the increase of storage time and temperature,the electrical conductivity,fatty acid value and malondialdehyde content of rice grains under different storage conditions showed an increasing trend;while the crude fat content,non-starchy lipid content,lipid oxidase activity,catalase activity and peroxidase activity all showed a decreasing trend.The correlation analysis of different indicators showed that fatty acid value,malondialdehyde content and electrical conductivity were positively correlated with each other,and highly significantly negatively correlated with crude fat content and non-starchy lipid content.This indicates that there is a highly significant correlation between rice lipids and rice aging.(2)To study the changes of fatty acid fractions and edible quality of rice grains under different storage conditions.A total of five fatty acid fractions were detected by GC-MS:myristic acid,palmitic acid,stearic acid,oleic acid and linoleic acid.Myristic acid,palmitic acid,stearic acid and oleic acid content all showed highly significant positive correlation with storage time;linoleic acid content showed highly significant negative correlation with storage time.The taste value of rice was found to decrease gradually with increasing storage time by rice taste meter.The correlation analysis revealed a highly significant positive correlation between rice taste value and crude fat,non-starch fat and linoleic acid content;and a highly significant negative correlation with myristic acid,stearic acid,palmitic acid and oleic acid content.This indicates that a decrease in fat content leads to a decrease in the edible quality of rice.(3)The changes in the amount of mycorrhizal fungi in rice under different storage conditions were studied.With the extension of storage time and the increase of storage temperature,the amount of mycobacteria in rice grain gradually increased and reached the highest value at 240 d.The correlation analysis found that the amount of mycobacteria in rice grain correlated with storage time and storage temperature.The correlation analysis showed that the amount of mold was positively correlated with storage time and storage temperature.The correlation between the amount of mold and fatty acid value was highly significant,and the correlation between the amount of crude fat and non-starchy fat was highly significant and negative.It indicates that the mold will decompose the fat in the rice during the storage process and produce free fatty acid,which will increase the fatty acid value.(4)The effects of storage pest infection on the lipid changes of rice grains were studied.The results showed that the electrical conductivity,fatty acid value and malondialdehyde content of rice grains tended to increase with the increase of infestation time and population density;the crude fat content,catalase activity and peroxidase activity all tended to decrease.Correlation analysis of each index revealed that there was a highly significant correlation between crude fat content and each index,indicating that there was a correlation between the changes in quality and the changes in fat content after the corn weevil infested the rice grains.