Cryoprotective effect of curdlan on frozen wheat gluten: With respect to physicochemical properties and molecular structure

Curdlan alleviates the quality deterioration of frozen dough during storage by a mechanism related to retarded migration of moisture. However, the strengthening effect of curdlan on the gluten structure needs to be proved. Therefore, the effect of curdlan on physicochemical properties and molecular structure changes of frozen wheat gluten was investigated. Frozen storage resulted in decreased water-holding capacity and viscoelasticity properties, as well as increase in oil-holding capacity and surface hydrophobicity. However, curdlan significantly inhibited the rheological and physicochemical properties changes of gluten. Scanning electron microscope results showed that the structure of gluten with curdlan had relatively smoother and less damaged surface during frozen storage. Curdlan alleviated the depolymerization of gluten macropolymers (GMP) by restraining the breakage of S-S bonds, with GMP depolymerization degree of 20% after 90 days of storage, significantly lower than that of the control (38%). Curdlan restrained the transition of alpha-helix to beta-turn and antiparallel beta-sheet, and suppressed the protein unfolding and chromophores exposure. Curdlan interacted with gluten prominently by hydrogen bonds, followed by hydrophobic interactions, thus strengthening the gluten structure. Alleviation of dough quality loss during frozen storage by curdlan could be related to its strengthening gluten structure.