Alkali-Extracted Feruloylated Arabinoxylans from Nixtamalized Maize Bran Byproduct: A Synonymous with Soluble Antioxidant Dietary Fiber

Feruloylated arabinoxylans were obtained from nixtamalized maize bran under alkaline conditions (0.5 N NaOH) at different times (2 h, 4 h and 6 h). They were analyzed for neutral sugars composition, dietary fiber and ferulic acids content, as well as the antioxidant capacity, to establish if they can be considered as soluble antioxidant dietary fiber. The yields of the arabinoxylans following alkaline extraction treatments were 4.89%, 8.23% and 7.17% for 2 h, 4 h and 6 h, respectively. The purity of arabinoxylans ranged from 55.58 to 61.16%, while arabinose to xylose (Ara/Xyl) ratio ranged from 0.82 to 0.87 which indicated that all arabinoxylans had a moderately branched structure. The soluble dietary fiber accounted for more than 85% of the chemical composition of feruloylated arabinoxylans. Monomeric and oligomeric forms of ferulic acid were influenced by the alkali extraction time. The monomeric form was the main phenolic acid in feruloylated arabinoxylans (77.05-86.97%), followed by dimers (11.57-14.20%), and trimer (0.93-9.36%). Total phenols ranged from 9.01 to 6.48 mg FAE/g, while antioxidant capacity ranged from 29.49 to 31.69 mu mol TE/g, 16.60 to 21.27 mu mol TE/g, 39.23 to 58.33 mu mol TE/g and 17.03 to 60.65 mu mol TE/g in DPPH, ABTS, FRAP and ORAC methods, respectively. The phenol content and antioxidant capacity were in the order: 2 h extract > 4 h extract > 6 h extract and in accordance to the ferulic acid content. The results indicated that alkali extracted feruloylated arabinoxylans obtained from nixtamalized maize bran byproduct are synonymous with soluble antioxidant dietary fiber.