FOOD SCIENCE ›› 2021, Vol. 42 ›› Issue (21): 46-55.doi: 10.7506/spkx1002-6630-20200902-023

• Basic Research • Previous Articles     Next Articles

Synthesis, Characterization and Antioxidant Activity of Millet Bran Soluble Dietary Fiber-Cr(III) Complexes

QUAN Zhigang, WANG Weihao, ZHAO Shuting, LIU Dezhi, WANG Yifei, WU Yunjiao, SU Youtao, WEI Chunhong, CAO Longkui   

  1. (1. College of Food Science, Heilongjiang Bayi Agricultural University, Daqing 163319, China; 2. National Coarse Cereals Engineering Research Center, Daqing 163319, China)
  • Online:2021-11-15 Published:2021-11-23

Abstract: Soluble dietary fiber (SDF) extracted from millet bran by enzymatic hydrolysis was coordinated with trivalent chromium ions in a weakly alkaline environment to produce SDF-Cr(III) complexes. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) were used to characterize the structures of SDF and SDF-Cr(III) complexes. Gel permeation chromatography (GPC) and high-performance liquid chromatography (HPLC) were used to determine their molecular mass distribution and monosaccharide composition. Their in vitro antioxidant properties were measured by 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH) radical, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicla cation, and hydroxyl radical scavenging capacity and total antioxidant capacity. The results showed that the surface structure of SDF-Cr(III) was loose and porous, exhibiting a decrease in the aggregation degree of island-like bulges and more scattered intermolecular arrangements compared to SDF. A large difference was found between SDF and SDF-Cr(III) in functional groups. According to FTIR analysis, SDF-Cr(III) showed reduced stretching vibrations of the active functional groups (hydroxyl, ester, and carbonyl groups), a blue shift in the absorption maximum, and a Cr-O stretching vibration at 530.27 cm-1, confirming the binding Cr3+ to SDF. The number average molecular mass (mn), weight average molecular mass (mw) and molecular mass distribution width index (D) of SDF was 0.195 × 104 Da, 0.940 × 104 Da, and 4.81, while those of SDF-Cr(III) were 0.742 × 104 Da, 4.708 × 104 Da and 6.35, respectively as determined by GPC. HPLC showed that the relative content of monosaccharides in SDF-Cr(III) was higher than that in SDF. SDF-Cr(III) had stronger in vitro antioxidant properties compared to SDF. In conclusion, millet bran SDF-Cr(III) may have the potential to be developed into health products with hypoglycemic effect.

Key words: millet bran; soluble dietary fiber; complex; structure; antioxidant activity

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