Effect Of Rapeseed Pretreatment On Rapeseed Polyphenols And Rapeseed Oil Flavor

Rapeseed is rich in polyphenols,among which the most important endogenous polyphenols are erucic acid and erucic acid,but different environments can bring about changes in these polyphenols;erucic acid is hydrolyzed under high temperature and high pressure conditions to produce erucic acid,and erucic acid is decarboxylated under high temperature and high pressure conditions to produce Canolol.in order to better utilize the polyphenols and Canolol in rapeseed oil and improve the quality of rapeseed oil,this paper Firstly,the method of determining the content of erucic acid,erucic acid and Canolol in canola oil using high performance liquid chromatography was explored;microwave treatment was used to improve the polyphenols of canola oil,and the effects of four factors,namely microwave power,microwave time,initial moisture and material thickness,were investigated to optimize the process conditions by response surface;combined with the microwave treatment process,the addition of ascorbic acid,EDTA-2Na,Zn²⁺,p H adjustment value and ultrasonic assisted treatment to explore the further improvement of total phenol and Canolol content in canola oil,and also to investigate and analyze the changes of erucic acid and erucic acid content and odor characteristics of canola oil in canola oil and canola cake.The results were studied as follows:（1）The high performance liquid chromatographic conditions for mustard acid,mustard base and Cananolol were determined by the methodological study as follows:2%acetic acid in water as mobile phase A,methanol as mobile phase B,gradient elution,elution program:0min:90A%-10B%;0-10 min:70A%-30B%;10-30 min:60A%-40B%;30-40 min:60A%-40B%;40-50min:40A%-60B%;50-55min:100B%;55-65min:90A%-10B%;65-70min:90A%-10B%;column temperature was 30℃;elution flow rate was 0.85 m L/min;UV detection wavelength:322 nm for mustard acid,320 nm for mustard base and 278 nm for Canolol.The linearity was good in the range of 0.5-50μg·m L^-1（R2=0.9999）for erucic acid,0.8-200μg·m L^-1（R2=0.9998）for erucic acid and 5-500μg·m L^-1（R2=0.9994）for Cananolol.The RSD values of repeatability and stability were less than 3%in the range of 0.17%-1.67%.The mean spiked recoveries of the three standards at three concentration levels,low,medium and high,were 97.42%-101.5%with RSD values of 0.16%-0.68%.The limits of detection were 0.2μg·m L^-1,0.32μg·m L^-1and 2μg·m L^-1for erucic acid,erucic acid and Canolol,respectively;and the limits of quantification were 0.5μg·m L^-1,0.85μg·m L^-1and 5μg·m L^-1,respectively.（2）The best process to improve the content of polyphenols and Cananolol in rapeseed oil is:microwave efficiency 640 W,microwave time 6 min 30 s,material thickness 1.5 cm,initial moisture 9%.The total phenolic content under this condition was 2217.87μg.g^-1and Canolol content was 1403.66μg.g^-1.（3）The content of total phenols and Canolol in canola oil obtained after pressing was increased by soaking canola seeds with the addition of ascorbic acid,Zn²⁺,EDTA-2Na and p H adjustment,except for the addition of Zn²⁺which had almost no effect.Then,on the basis of this,ultrasound was used to assist,and the results showed that ultrasound was beneficial to increase the content of total phenols and Cananolol in rapeseed oil.The maximum contents of total phenols and Cananolol were increased by 3.25%and 6.81%,respectively,compared with those without ultrasonic treatment.The volatile flavor substances of canola oil obtained from the different pretreatment methods in this chapter were investigated using an electronic nose and a gas chromatography-mass spectrometer.It was found that the electronic nose could distinguish some of the samples but not completely and effectively between the nine samples,so the flavor substances were analyzed by GC-MS.It was found that there was little difference in the types of flavor substances and a large difference in their contents.All samples were detected by GC-MS to contain 51 flavor substances,including 18 heterocyclic substances,11 aldehydes,10 thioside degradation product substances,5 acids,3 phenols,3esters,and 1 ketone.The largest proportion of thioside degradation products was 48.53%,followed by heterocyclic substances,acids,aldehydes,ketones,phenols,and esters.In order to analyze the key flavor substances affecting this strong flavored canola oil,18 flavor substances with ROAV>0.1 were selected from 269 compounds in 9 samples for factor analysis using SPSS software.A total of 5 main components were extracted,and the main volatile substances of canola oil were hexanoic acid,nonanal,hexanal,5-methylfuranal,2-acetyl pyrrole,4-hydroxy-2,5-dimethyl l-3（2H）-furanone,isoeugenol,2,6-dimethoxyphenol,2-pyrrole formaldehyde,2-methylpyrazine,2,3,5-trimethylpyrazine,2,3,5-trimethylpyrazine,trans-2,4-decadienal,furfural,2-acetylpyrazine.