Effects of konjac glucomannan on heat-induced changes of wheat gluten structure

•Konjac glucomannan could protect specific secondary structure of gluten.•Konjac glucomannan shows biphasic effect on gluten at different temperatures.•Konjac glucomannan could mitigate heat-induced denaturation.•Konjac glucomannan is unable to form covalent bonds with gluten.•Konjac glucomannan chains might limit the flexibility of protein molecules.

Effects of konjac glucomannan on the structure of wheat gluten were investigated at variable temperatures in this study. Dynamic oscillatory rheology study showed that konjac glucomannan conferred stiffness on gluten with a higher tan δ data at 25 °C and 55 °C, but this parameter was lower at 75 °C and 95 °C. Konjac glucomannan decreased the content of thiol equivalent groups and increased the α-helix/β-sheet content ratio, respectively. The thicker layer of gluten protein with 5% konjac glucomannan was observed by scanning electron microscopy. This study revealed that konjac glucomannan could alter the conformations of gluten proteins upon heating via non-covalent interactions and physical entanglements. It is likely that konjac glucomannan promotes protein aggregation by strengthening hydrophobic interaction at 25 °C and 55 °C, and alleviates heat-induced denaturation by decreasing the flexibility of polypeptide chain at higher 75 °C and 95 °C.