Research On Determination Of Nutritional Components In Rapeseed And Sesame Based On Metabolomics

Edible oils play an irreplaceable role in dietary life,providing with not only energy and essential fatty acids,but also functional nutrients such as fat-soluble vitamins,phytosterols,polyphenols and tocopherols.With the improvement of people's living standards and the enhancement of health awareness,high-quality,nutritious and healthy edible vegetable oils are favored by consumers.The quality of edible vegetable oil depends on the content of characteristic nutrients in the oilseeds.Therefore,discovery and use of these characteristic nutrients of vegetable oilseeds has become the key technologies to industrial development.However,there were few reports on the composition and mechanism of characteristic nutrients in oilseeds,which has become a bottleneck restricting the development and evaluation of high-quality edible oil.Therefore,it is of great significance for improving the quality of edible oil,meeting the quality requirements of consumers,and promoting the development of oil industry to excavate the characteristic nutrient components in oilseeds.In this thesis,taking the common oilseed of rapeseed and the special oilseed of sesame as the research objects,the high-sensitivity simultaneous determination of multiple functional nutrients was developed,and the environmental factors and formation mechanism affecting the accumulation of nutrients were preliminarily investigated.The detailed research contents are as follows:1.Folin-Ciocaileu colorimetric determination method and near-infrared rapid determination method of total phenol contents in rapeseed were established and employed to analyze the rapeseeds from main producing aera to discover the environmental factors affecting the total phenol content in rapeseeds.The extraction time,extract concentration and solid-liquid ratio were optimized by single factor experiment.The optimal extraction process was obtained:50%methanol solution was used as extract,the ratio of material to liquid was 1:20?g/mL?,and the extraction time was 3 h.332 rapeseeds from 14 provinces of main rapeseed producing areas was determined,and their near-infrared spectra were collected.The near-infrared prediction model of total phenol contents in rapeseed was established by partial least squares method.Root Mean Squared Error of Cross Validation?RMSECV?of the model was 124.54 mg/kg,and the coefficient of determination?R²?was 0.9728,indicating that the model prediction results are reliable.Comparing the average total phenol contents in rapeseeds from different provinces,it was found that the total phenol content of rapeseeds in Shaanxi,Chongqing and Zhejiang provinces was higher.Correlation analysis between total phenol content of rapeseeds and environmental factors indicated that the key environmental factors affecting total phenol content were the highest surface temperature and daily average pressure in one month before harvest.The high surface temperature is conducive to the accumulation of phenolic compounds in rapeseeds,and the high pressure impedes the accumulation of phenols.It provides important technical supports for the accurate and rapid determination of total phenol content in rapeseeds,the cultivation of high phenol rapeseed varieties and the delineation of dominant production areas.2.The idea of quantification using isotope ion was proposed to establish a targeted metabolomic method for main phenolic compounds in rapeseeds,which overcame the difficulty of simultaneous quantification of micro and trace components.Simultaneous quantitative detection of 13 kinds of compounds in metabolic pathway from phenylalanine to sinapine was proposed.The methodological investigation found that the limit of detection was 0.01-9.84?g/kg,the limit of quantification was0.03-32.8?g/kg,and the intra-day precision and inter-day precision were 1.5%-8.4%and 3.3%-14.4%,respectively.The recoveries ranged from 81.9%to 117.2%,and the matrix effects ranged from-11.5%to 13.7%,which indicated that the method has high sensitivity and good stability,and the recoveries and matrix effects could meet the analysis requirements of actual samples.Metabolic difference analysis showed that there was a significant difference in the content of phenylalanine and sinapine between high and low total phenol rapeseeds.That means that sinapine is the main cause of the difference in total phenol content of rapeseeds Sinapine can be converted into canolol during processing,which greatly improves the nutritional quality of rapeseed oil.This method provides a basis for the in-depth study of the regulation mechanism of polyphenol formation in rapeseeds,and also provides a reference for the simultaneous quantitative analysis of other micro and trace components.3.The central design method was used to optimize the simultaneous extraction process of different kinds of compounds,and the simultaneous detection method of 10 characteristic nutrients in sesame seeds was established to discover the characteristic nutrients in black sesame seeds such as coniferyl aldehyde and phloretin.Ultrasonic extraction of differential compounds of black and white sesame seeds was optimized by single factor experiment,Plackett-Burman design and Box-Behnken design experiment.The optimal extraction conditions were determined:methanol concentration of 75.0%,liquid to material ratio of 20:1?mL/g?,ultrasonic temperature of 50°C,ultrasonic time of 65 min,and ultrasonic power of 410.0 W,and one round of extraction.The mobile phase used was 0.1%formic acid acetonitrile and 0.1%formic acid in water,and the column was a Thermo Syncronis C18 reverse phase column?100 mm×2.1 mm,3?m?.The target compounds were separated and determined within 7minutes.The results showed that the content of vitamin B₂,phloretin,hesperidin,L-hyoscyamine,and coniferyl aldehyde in black sesame seeds was significantly higher than that of white sesame seeds.This study provides important testing technology support for the selection of high-quality sesame varieties and the development of functional products.