Antioxidant and aflatoxin B1 adsorption properties of Eucheuma cottonii insoluble dietary fiber

The residue of Eucheuma cottonii after extracting carrageenan contained up to 90% insoluble dietary fiber, so it could be used as an excellent source of dietary fiber. To improve its performance, the E. cottonii insoluble dietary fiber (EIDF) was superfine pulverized to get five samples ranging from 40 to 300 mesh (E40–E300). The particle structure of E100–E300 became loose and more pores exposed; meanwhile, their crystallinity decreased from 53.60% to 43.86–43.40%. Antioxidant activity determination showed that EIDF had extremely strong hydroxyl free radical scavenging ability with the scavenging rate of all EIDFs higher than 97%. Aflatoxin B1 (AFB1) adsorption study showed that superfine EIDF had better aflatoxin adsorption capacity, especially E100. It could adsorb 82.5% aflatoxin within 15 min when loading 2 μg AFB1/mL and the adsorption conformed to pseudo second-order kinetic model, suggesting the chemisorption. When loading up to 20 μg AFB1/mL, its adsorption capacity reached 0.789 mg/g, showing favorable adsorption on homogeneous surface. The adsorption was most effective at pH 7.0 and 25 °C. Thereby, the superfine EIDF is an excellent AFB1 adsorbent and antioxidant and may have potential applications in food, feed and medicine.