Abstract: The purpose of this study was to investigate the influence of antifreeze proteins (AFPs) on protein characteristics and the states of water in frozen dough during frozen storage and freeze-thaw cycles by using Ellman’s colorimetric method, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). Results showed that the free sulphur content in frozen dough rose while the disulfide bond content decreased after frozen storage and freeze-thaw cycles. Adding AFPs had no effect on the protein subunits. With increasing frozen storage time, the content of intermolecular β-sheet increased whereas the content of β-turn structure dropped. Freeze-thaw cycles decreased the content of α-helix structure. Frozen dough with added AFPs showed smaller changes in all protein characteristics compared with the control sample with no added AFPs. The water loss rate in the control sample remarkably increased; the relaxation time T21 became greater with frozen storage time and the bound water content decreased. These findings illustrate that AFPs could inhibit disulfide bond rupture and changes in protein secondary structure, restrain the recrystallization of ice crystals, prevent water loss from the dough, and maintained the water-holding capacity of the dough.

Key words: frozen dough, antifreeze proteins, frozen storage and freeze-thaw cycle, protein structure