Study On The Molecular Mechanism Of Canolol Formation In Rapeseed Under Microwave Physical Field

Rapeseed is the most important oil crop in China.Rapeseed oil is also regarded as the most popular edible oil for its reasonable fatty acid composition and abundant nutrients.However,it is under-used owing to high temperature processing,poor product quality and low efficiency.Microwave pretreatment was benefit to improving the yield,flavor and nutrient content of rapeseed oil.Above all,a new substance named 2,6-dimethoxy-4-vinylphenol(canolol)was generated.Canolol can be dissolved in vegetable oils and shows a good antioxidant property.Meanwhile,it possesses anti-cancer,anti-tumor,antiinflammatory,improving cognitive ability and other functions.At present,the researchers in the world are focusing primarily on structure identification and quantitative analysis,physiological function evaluation,and the effect of microwaved conditions on canolol formation,while the study of canolol formation mechanism is rare.This thesis round the problem of canolol formation mechanism launched a series of research between canolol and sinapic acid and its derivatives aiming to reveal the material basis and formation mechanism of canolol.Based on the canolol formation mechanism and the physicochemical properties of sinapic acid derivatives,new regulations were proposed to increase the canolol content in rapeseed under microwave physical field.1.Study on distribution of specific polyphenols sinapic acid and derivatives in rapeseed The main specific polyphenols sinapic acid derivatives in rapeseed were sinapine(SP),1-O-sinapoyl-?-Dglucoside(SG),kaempferol sinapoyl triglucosides(QSDG),sinapoyl malate(SM),1-O-sinapoly-?-Dglucoside-(2?1)?-D-fructoside-1-O-sinapoly(DDSG)and 1-O-sinapoly-?-D-glucoside-2-O-sinapoly(DSG).Distribution of sinapic acid and derivatives in Zhongyouza No.19(Brassica napus),Longyou No.7(Brassica campestris)and Gaoyou No.9(Brassica juncea)were significantly different.SP in Zhongyouza No.19 was less than that of Longyou No.7 and Gaoyou No.9,however,other sinapic acid derivatives was significantly higher.After microwave pretreatment,canolol in Zhongyouza No.19 is the highest among three rapeseeds.Sinapic acid and its derivatives in hull,kernel and endosperm of Zhongyouza No.19 were also significantly different.Hull showed the less sinapic acid derivatives than kernel and endosperm.The highest content of SP,DDSG and DSG was the endosperm,and the highest content of SG,SA and SM was the kernel.2.Study on material basis of canolol formation in rapeseed under microwave physical field The contents of SP,SG,QSDG,SA,SM,DDSG and DSG in rapeseed were 559~1145 mg/100 g,3.11~138 mg/100 g,29.0~61.6 mg/100 g,9.29~54.2 mg/100 g,7.00~111 mg/100 g,14.3~72.7 mg/100 g and 4.72~60.5 mg/100 g,respectively.Overall,the content of major sinapic acid derivatives in rapeseed from high to low was: SP,SG,DDSG,QSDG,SM,DSG,and SA,which account for 79.46%,5.2%,4.29%,and 3.66%,2.77%,2.61% and 2.01%,respectively.After microwave pretreatment,canolol in pressed rapeseed oil increased 76.8 times,which was significantly different in various varieties,highly up to 16 times.Other sinapic acid derivatives in rapeseed except for QSDG undergone pyrolysis in varying degrees.The results of correlation analysis results showed that canolol formation was related with SG,SM,DDSG,and DSG in rapeseed under microwave physical field.3.Study on the molecular mechanism of canolol formation in rapeseed under microwave physical field SG,SM,DDSG,and DSG were the main precursors of canolol in rapeseed under microwave physics field.The above substances undergone ester bond breakage to produce the intermediate product SA under thermal conditions,which was further thermally decarboxylated to produce canolol.During the formation of canolol,SG,SM,DDSG and DSG exhibited different pyrolysis temperature,canolol formation efficiency and pyrolysis products attributed to the different structure.Canolol was in a dynamic process during rapeseed microwave pretreatment,it meant that canolol was generated and accompanied by its pyrolysis.2,6-dimethoxyphenol,3,5-dimethoxybenzyl alcohol and 4-hydroxy-3,5-dimethoxybenzaldehyde were the main products of canolol pyrolysis.4.Study on regulations of canolol in rapeseed under microwave physical field Aqueous solution with pH 2~7 could be used to adjust the moisture content before microwave pretreatment and give preference to pH 6.The alkaline condition should be avoided in the process of canolol-rich oil preparation.The appropriate concentration of L-ascorbic acid solution can increased canolol content in microwave rapeseed significantly.Canolol undergone volatilization and pyrolysis in thermal condition,the enclosed environment was benefit to reducing the loss of canolol under thermal environment.Semienclosed microwave pretreatment could enhance the canolol content in microwaved rapeseed significantly,up to 12.7%.Taking cost,energy consumption,operability,canolol content and rapeseed oil quality into account,semi-enclosed microwave pretreatment can be used as the preferred regulation measure.In conclusion,distribution and profile of specific polyphenol sinapic acid and its derivatives in different variety of rapeseeds were significantly different,so did the different parts(hull,kernel and endosperm).The different variety of rapeseeds exhibited different canolol formation efficiency which was related to sinapic acid and its derivatives under microwave physical field.SG,SM,DDSG and DSG were the main material basis of canolol formation,the ester bond of the above substances was cleaved to generate the intermediate product SA.SA is further thermally decarboxylated to form canolol under microwave physical field.During this process,canolol was in a dynamic state which meant that canolol was generated and accompanied by its pyrolysis.2,6-dimethoxyphenol,3,5-dimethoxybenzyl alcohol and 4-hydroxy-3,5-dimethoxybenzaldehyde were the main products of canolol pyrolysis.Semi-enclosed microwave pretreatment can be used as the preferred regulation measure for improving canolol content significantly.