Effect Of Steam Explosion Treatment On Wheat Bran Phenolic Compounds And Antioxidant Capacity

This topic mainly studies the effect of steam explosion treatment on wheat bran phenolic compounds and physiological active capacity, also optimizes the extraction methods of phenolic compounds from wheat bran. The main three aspects were shown as follows:The effects of steam explosion treatment(SET) on the phenolic acid composition and antioxidant activities of wheat bran were investigated in this study. The SET was performed at different pressures(0.5 MPa, 1.5 MPa, 2.5 MPa) and different residence times(30 s, 90 s). The phenolic compounds in wheat bran were extracted into two fractions by methanol extraction and alkaline hydrolysis, the free phenolic acids and the phenolic acids released from the soluble ester. Different fractions contained different phenolic acid profiles. High-performance liquid chromatography(HPLC) was used for analysis of main phenolic acids(vanillic acid, syringic acid, 4-coumaric acid, ferulic acid) before and after steam explosion in 280 nm and 320 nm. The results indicate that the contents of main phenolic acids increased with SET. They also increased dramatically when wheat bran was treated under 2.5 MPa, 30 s, after which they decreased. The total phenolic content of the sample increased with increasing SET to reach a peak at 2.5 MPa, 30 s, after which it decreased. The highest content was 28 mg/g. Several authoritative methods of antioxidant capacity gave the consistent conclusion, compared with the untreated sample, the treated wheat bran shows the higher DPPH and ABTS radical scavenging activities, antioxidant activity in a linoleic acid system and reducing power. When the wheat bran is treated at 2.5 MPa with 30 s, the release contents of phenolic acids reach the best and the antioxidant activity reach the highest.To use response surface methodology to optimize the extraction of the phenolic compounds in wheat bran treated by steam explosion, and to determine the antioxidant activity of the extract obtained. By using response surface methodology, the effects of extraction time, methanol concentration, liquid/solid and temperature were studied and optimized. DPPH radical-scavenging capacity, reducing capacity and ABTS radical scavenging capacity were also employed to determine antioxidant activity of the extract. Results showed that under the optimal conditions, i.e., extraction time: 120 s, ethanol content: 43 %, liquid/solid: 35:1, temperature: 70 oC, the experimental total phenolic yield was 30.464 ± 0.025 mg/g, which agreed with the predicted value of 31.687 mg/g. The phenolic compounds showed strong antioxidant activities. At extract concentration of 1 mg/ml, DPPH radical-scavenging activity was 50 %. Although its reducing power(2 –10 mg/m L) was lower than that of BHA, ABTS radical scavenging of the extract was higher than that of BHA at extract concentration > 6 mg/m L.The effect of steam explosion treatment(SET) on the phenolic composition, antioxidant activity and antiproliferation to Hep G2 of wheat bran was investigated in this part. It was found that moderate SFE treatment could significantly enhance the total phenolic content of wheat bran. After SFE pretreatment, the free and conjugated ferulic acid contents in the wheat bran were significantly increased observed through HPLC. The chemistry antioxidant activities of SET pretreated wheat bran were higher than those untreated wheat bran. The cellular antioxidant and antiproliferative activities of SET treated wheat bran were also significantly ameliorated.