Comparative study of cross- and uncross-linked arabinoxylans extracted from maize bran with special reference to their structural and antioxidant potential

Abstract

Maize bran is a by-product obtained after the milling of maize kernels and separated as by-product. The current research aimed to extract and characterize the arabinoxylans (AXs) and their gels from maize bran. Initially, maize bran was evaluated for its proximate composition and dietary fiber profile. Then, AXs were extracted through alkali extraction method, and in vitro gelation of AXs was performed through enzymes (laccase from Termites versicolor). Their structure was characterized through Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). Further, the phenolic compounds and their activity was assessed through three different assays including diphenyl picryl hydrazyl (DPPH), ferric reducing antioxidant power (FRAP), and ABTS+. The results regarding the chemical composition of maize bran showed that maize bran majorly comprised moisture, ash, crude fat, fiber, crude protein and nitrogen-free extract with 10.13 ± 0.46, 1.87 ± 0.15, 1.26 ± 0.26, 7.53 ± 1.00, 12.67 ± 0.75, and 66.54 ± 0.82 g/100 g of the sample. Further, dietary fiber profile showed that maize bran comprised 6.97 ± 0.5 and 35.20 ± 4.1% soluble and insoluble fractions of dietary fibers. Then, the structural characterization of maize bran through FTIR spectroscopy showed a typical spectrum and presented the peaks at different wavelengths, which was similar to structural features as described in previous studies. Surface morphology of gel through SEM showed micrographs with small pores, which according to our information was formed due to laccase (enzymes) activity. However, quantification of polyphenols including total phenolic content and total flavonoid content showed the results including 6.42 ± 0.18 GAE/g and 1.84 ± 0.66 CE/g and their activity assessed through DPPH, FRAP, and ABTS+ assays showed the values including 31.62 ± 0.16, 34.87 ± 0.18, and 14.21 ± 0.18 μmol TE/g, respectively. The results in this study showed that maize bran AXs and their gels showed an interesting trend in their structural and antioxidant potential.