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Antioxidant capacity, phenolics and isoflavones in soybean by-products

Tyug, Tan Seok, Prasad, K. Nagendra, Ismail, Amin
Food chemistry 2010 v.123 no.3 pp. 583-589
gallic acid, nutrient content, dietary fiber, isoflavones, protein content, vanillic acid, food grades, carbohydrate content, soybeans, ash content, water content, proximate composition, food composition, soymilk, powders, antioxidant activity, ferulic acid, hulls
This study aimed to determine proximate composition, antioxidant capacity, total phenolic content, isoflavones and free phenolic compounds in soy by-products. High carbohydrate and protein contents were found in grade A soymilk powder (GASP) compared to grade B soymilk powder (GBSP) and soy husk powder (SHP). Ash, moisture and total dietary fibre contents were reported to be the highest in soy husk, while GBSP had the highest fat content. Antioxidant capacity as assessed using β-carotene bleaching assay was in the order of SHP≈GBSP>GASP, and the ranking order of the Trolox Equivalent Antioxidant Capacity (TEAC) value was GASP≈GBSP>SHP, while the Ferric Reducing Antioxidant Power (FRAP) value was GASP>GBSP>SHP. The total phenolic content was in the range of 62.44-103.86mg GAE/100g wet weight, and the major phenolic compounds in free form were ferulic, vanilic as well as gallic acids. Acid hydrolysis increased the amount of total extractable isoflavone in all soy samples.