Effect of three soluble dietary fibers on the properties of flaxseed gum-based hydrogels: A comparison study and mechanism illustration

As a new type of natural edible hydrocolloid, the gel formed by flaxseed gum (FG) has some defects including poor water holding capacity and high hardness. The combination of FG with other polysaccharides is usually one of the ways to improve these drawbacks. In this study, three soluble dietary fibers (SDFs), namely, konjac glucomannan (KGM), guar gum (GG) and psyllium seed gum (PSG), were selected and mixed with FG at three different concentrations to form FG-SDF hydrogels. The effects of different SDFs on gelling properties of FG and possible mechanisms were compared. All SDFs increased water holding capacity and binding degrees with water molecules of FG-based hydrogels, and the growth became more pronounced with increasing SDF concentration. Compared with control sample (FG hydrogel), FG-PSG hydrogels and FG-GG hydrogels exhibited weaker gel strength, hardness and elasticity, while FG-KGM hydrogels showed the opposite results. FTIR spectra demonstrated an obvious cross-linking occurred between SDFs and FG in FG-SDF hydrogels, and the degree of cross-linking depended on the concentration of SDF. It was deduced that SDF could extend in water while heating, thus compete with FG to form hydrogen bonds to inhibit self-cross-linking of FG. In general, the obstructive effect followed the order of PSG > GG > KGM.