Abstract
Purpose : 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. Methods : By using response surface methodology, the effects of extraction time, methanol concentration, liquid/solid and temperature were studied and optimized. 2,2-Diphenyl-1-(2,4,6- trinitrophenyl) hydrazyl (DPPH) radical-scavenging capacity, reducing capacity and 2,2′-Azino-bis(3- ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radical scavenging capacity were also employed to determine antioxidant activity of the extract. Results : Under the optimal conditions, i.e., extraction time: 120 s, ethanol content: 43 %, liquid/solid: 35:1, temperature: 70 o C, the experimental total phenolic yield was 30.464 ± 0.025, which agreed with the predicted value of 31.687. 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/mL) was lower than that of BHA, ABTS radical scavenging of the extract (close to 90 %) was higher than that of BHA at extract concentration > 6 mg/mL. Conclusion : The yield of the phenolic compounds was high and the compounds displayed strong antioxidant capacity, which indicates that the extraction of wheat bran under steam explosion holds high potentials for the food and pharmaceutical industries. Keywords : Wheat bran, Steam explosion, Extraction, Response surface methodology, Antioxidant capacity
Highlights
Wheat bran is one of the main by-products of the wheat-milling industry
Ferulic acid was the dominant phenolic acid in wheat bran which accounted for 59–60% of the total phenolic acids on a per weight basis [3]; it is an excellent free radical scavenger and has the antioxidant capacity [1]
Response surface methodology (RSM) with appropriate experimental designs, e.g., central composite design (CCD), is a method based on mathematical statistics theory, which has been widely used to optimize the intended parameters in the extraction and modification of bioactive compounds in grain and oil food, chemistry and other aspects [6,9]
Summary
Wheat bran is one of the main by-products of the wheat-milling industry. Wheat bran fiber contains many antioxidants, these substances are mainly phenolic compounds, total amount can be as high as 500 mg/kg [1]. The wheat phenolic compounds are mainly phenolic acids, flavonoids and lignans. Ferulic acid was the dominant phenolic acid in wheat bran which accounted for 59–60% of the total phenolic acids on a per weight basis [3]; it is an excellent free radical scavenger and has the antioxidant capacity [1]. Steam explosion is beneficial for the release of cellulose and hemicelluloses, because of the combination between phenolic acids and cellulose. Steam explosion treatment is beneficial for the release of phenolic acids
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