A Comparative Study On The Quality Of Rapeseed From Different Producing Areas

As a local oil crop,rapeseed is widely cultivated in our country and has a very high yield.It has reached the world’s leading level.Rapeseed oil contains high amounts of unsaturated fatty acids,including oleic acid,linoleic acid andα-linolenic acid.The ratio of omega-6 toomega-3 fatty acids(2:1)that is beneficial to human health occurs naturally in rapeseed oil.Itis recommended to use rapeseed oil as cooking oil However,lipid oxidation leads to adecreased concentration of bioactive nutrients and the formation of unwanted compounds.This would deteriorate the quality of edible rapeseed oil,or even pose a hazard to human health.Chlorophyll and amino acids are important quality parameters of rapeseed.This paper establishes the rapid nondestructive detection technology of rapeseed chlorophyll and studies the effect of chlorophyll on lipid oxidation of rapeseed oil,and the comparative study on the amino acid composition of rapeseed in different producing areas,in order to quality rapeseed.Control provides a basis for improving the quality of edible oil.1.Rapid Detection of Chlorophyll Content in Rapeseed Based on Near Infrared SpectroscopyWith the advancement of mechanization of rapeseed production in China,chlorophyll content of rapeseed increases significantly due to the inconsistent maturity of silique,which directly affects the quality of rapeseed oil and increase the processing cost.Therefore,establishment of rapid and non-destructive detection techniques for chlorophyll in rapeseed is important to quality control of rapeseed oil.In this study,the chlorophyll contents of 450 representative rapeseeds were quantitatively analyzed by UV-Vis spectrophotometry.Subsequently,these rapeseeds were analyzed by near infrared spectroscopy(NIR).After the pretreatment of the first derivative and standard normal variate(SNV),and wavelength selection by competitive adaptive reweighted sampling(CARS),partial least squares(PLS)regression method was employed to construct the prediction model for chlorophyll content in rapeseed.The results of cross validation indicated that the coefficient of determination(Q~2)of validation set was 0.9446,while the mean square error of cross validation(RMSECV)was 1.36 mg/kg.The results indicated that this method could accurately determine chlorophyll content in rapeseed,which provides an important technological support to quality control of rapeseed oil.2.Effect of chlorophyll on lipid oxidation 1 of rapeseed oilThe residues of chlorophyll induce oxidative rancidity and deterioration through photo-oxidation.However,the effect of chlorophyll on the quality of rapeseed oil is still unknown.In this study,chlorophyll was added into rapeseed oil to reach the desired treatment levels of 2 mg/kg,5 mg/kg and 10 mg/kg,while no chlorophyll was added in the control sample.We investigated dynamic changes of the peroxide value of rapeseed oils with different chlorophyll contents exposed to light and stored in the dark at different times(0,1,5,10,15,20,25,30,35,31 45,50,55,and 60 days).The results showed that the peroxide value of rapeseed oil exposed to light increased significantly,especially for the oil with a high content of chlorophyll.In contrast,the peroxide value of rapeseed oil stored in dark was nearly unchanged no matter whether extra chlorophyll was added.This study showed that chlorophyll in rapeseed oil could trigger oil oxidation,and therefore it is necessary to take measures to reduce the chlorophyll content in rapeseed oil or store rapeseed oil in the dark as soon as possible.3.Comparative analysis of amino acid composition of rapeseed from different regionsTo study the differences of amino acids in rapeseed from different regions.According to GB 5009.124-2016,amino acids in rapeseed from Hubei province,Suzhou province,Sichuan province,and Guizhou province in the middle and lower reaches of the Yangtze river were detected using an automatic amino acid analyzer.Results showed Sichuan province rapeseed had the highest total amino acid content of(24.47±0.22)mg/100 mg,and the essential amino acid contents of rapeseed in each producing area accounted for more than 33%of the total amount of amino acids,of which the highest in Hubei province was highest(34.30%).The t-test showed that there were significant differences in different amino acids between these producing areas,among which cysteine(Cys)was the most significant amino acid in the differential amino acids.Therefore,the amino acid content and composition of rapeseed protein in different places have great differences.In the process of processing,rapeseeds from suitable places should be selected to improve its utilization.