Effect of triple helix polysaccharides from foxtail millet bran on millet starch gel formation

Polysaccharides as modifiers can solve native starch gel problem of weaker gel strength and lower gelation trend. The key structures of foxtail millet bran polysaccharides (FMBPs) in improving millet starch gel properties were investigated. Results showed that FMBPs were high molecular weight (Mw) heteropolysaccharides and the distribution of total sugar, uronic acid and monosaccharides was non-uniform in four FMBPs. Structural analysis revealed triple helix polysaccharides (THPs) existed in independent triple helix (ITH) and aggregates forms. The redshift degree of Congo red-FMBP complexes illustrated that FMBP-S1 contain the most ITHs, followed by FMBP-S2 and FMBP-S4, and the least in FMBP-S3. The porous structure of FMBPs promoted the adsorption of Congo red, bringing about the increase in weight and volume of the complexes and eventual precipitation. Separation of THPs provided a new method to investigate its role in starch gel. The results showed FMBPs with more ITHs showed higher peak viscosity, breakdown and setback. The presence of ITHs could reduce gel point temperature (ΔT = 6.62-29.86 °C) and water holding capacity (from 50 to 66 ms to 231 ms), but improve the viscoelasticity of gel. The study not only improved the quality of starch-based gel but also achieved high-value utilization of foxtail millet bran.