Determination Of Folic Acid Content In Maize And Analysis Of Its Variation Characteristics During Processing

Folic acid is a kind of essential B vitamin,which cannot be synthesized in human body.Lacking of folic acid can induce neural tube defects,neonatal neural tube defects and other health problems.Corn,one of the main food crops,is a good source of natural folic acid.However,there are few reports on the extraction and detection of folic acid from corn.Therefore,chemical method and three-enzymes method were used to extract folic acid from corn.The stabilities of folic acid and its derivatives were also studied.Then,the differences of folic acid content in corns from various origins and varieties were measured.And the changes of folic acid in corn during grain development and the effect of different processing methods on folic acid content were studied.This study could provide a theoretical basis for the intake of natural folic acid in corn and the monitoring of production process.The content of this article are as follows:?1?A chemical method was optimized to extract folic acid from corn by single factor and response surface test.The folic acid content was determined by high performance liquid chromatography?HPLC-UV?.The result showed the best extraction conditions were:temperature,42?;material-liquid ratio,1:11.7;extraction time,7.3 h;the consumption of activated carbon,1.2 g.The content of folic acid in corn was 1.68±0.05?g/g in the optimal conditions.The effect of various factors on the extraction of folic acid in corn were as follows:temperature>material-liquid ratio>time.?2?The enzymatic method was applied to extract folic acid from corn.Firstly,the extraction efficiencies of single enzyme,double enzyme,triple enzyme and different antioxidant combinations were compared.Then,the extraction conditions were optimized through single factor and orthogonal experiments.Moreover,the stabilities of folic acid?PteGlu?,tetrahydrofolate?H₄PteGlu?,5-methyltetrahydrofolate?5-CH₃-H₄PteGlu?and5-formyltetrahydrofolate?5-CHO-H₄PteGlu?were studied under different temperature,time and pH.The folic acid content was determined by high performance liquid chromatography-tandem mass spectrometry?HPLC-MS/MS?.The result showed that the three-enzymes method had the best extraction efficiency of folic acid in corn,and the antioxidant combination of vitamin C?Vc?and dithiothreitol?DTT?could better protect folic acid during the extraction process.The optimal extraction conditions of the three-enzymes method were:pH 7;?-amylase,150?L?20 mg/mL?;protease,350?L?4mg/mL?;the ratio of material to liquid,1:16?g/mL?;rat serum,200?L.Under the optimal extraction conditions,the contents of PteGlu,H₄PteGlu,5-CH₃-H₄PteGlu,and5-CHO-H₄PteGlu were 21.34,22.66,35.06,8.19?g/100g,respectively.Stability studies showed that pH had a greater effect on the stability of PteGlu,H₄PteGlu,5-CH₃-H₄PteGlu,and the effect of temperature and time were weaker.PteGlu was stable at pH 7 and H₄PteGlu and 5-CH₃-H₄PteGlu were stable at pH 6.5-CHO-H₄PteGlu was susceptive to temperature,which was stable at room temperature and 37?,and unstable at 100?.?3?The content of corn folic acid in different regions and varieties were determined.The three-enzyme method was used to extract folic acid from common corn in Hebei,Henan,Shanxi and Shandong provinces,and the content of folic acid in sweet and waxy corn with different grain colors were compared.The results showed that the total of folic acid and its derivative of 35 corn varieties in Hebei Province were quite different.The total contents of 4 kinds of folic acid were 25.90⁷3.44?g/100g.The highest content of PteGlu,H₄PteGlu,5-CH₃-H₄PteGlu and 5-CHO-H₄PteGlu were about 8.8,11.5,4 and 9.7times of their minimum content,respectively.The average content of corn folic acid in Hebei Province was 50.00?g/100g,the content of 5-CH₃-H₄PteGlu in corn was higher,while the content of 5-CHO-H₄PteGlu was lower.The difference of folic acid content in Zhengdan 958 corn planted in different areas of Hebei Province was significantly.The folic acids of corn in Henan,Shanxi and Shandong province were determined,and the total contents of the four kinds of folic acid were 36.00¹06.00?g/100g.Corn is greatly affected by the environment.The planting time,harvest time,soil,light,and rainfall in different provinces are different,which colud affect the quality and yield of corn,resulting in differences of folic acid content.The contents of folic acid in sweet and waxy corn of different grain colors were between 68.15⁹1.08?g/100g,and the average content was78.97?g/100g.?4?The changes of folic acid during corn grain development and the effects of different processing on folic acid content were investigated.The corn kernels of Jingnongke 728?Phase I and II?and Shiyu 348 were collected and analyzed by HPLC-MS/MS.The results showed that the overall folic acid content of corn kernels showed a downtrend.The folic acid content of Jingnongke 728?Phase I?increased slightly at 36 days after pollination;while Jingnongke 728?Phase II?showed an uptrend from 8 to18 days after pollination,and decreased after 18 days.The folic acid content of Shiyu348 corn kernels showed a downward trend after 12 days of pollination,and decreased significantly between 12 and 22 days of pollination.The downward trend tended to be gentle after 22 days of pollination.The processing methods of frying,steaming and cooking had a significant influence on the content of corn folic acid.The content of folic acid gradually decreased with the extension of processing time.Compared with different processing methods,the result showed steaming was better,followed by cooking,and frying was the worst.