抗冻蛋白对预发酵冷冻面团中蛋白质特性及水分状态的影响

采用Ellman’s试剂比色法、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳技术、傅里叶变换红外光谱技术以及核磁共振技术，研究冻藏和冻融循环条件下抗冻蛋白对冷冻面团的蛋白质特性以及水分子存在状态的影响。结果表明：经过冻藏和冻融循环，冷冻面团中游离巯基含量上升，二硫键含量下降。添加抗冻蛋白对冷冻面团亚基无影响。随着冻藏时间的延长，二级结构中分子间β-折叠含量增大，β-转角含量减小，而冻融循环使得α-螺旋结构含量下降，添加抗冻蛋白组的蛋白质特性变化均小于无添加组。无添加抗冻蛋白冷冻面团的失水率明显升高，驰豫时间随冻藏时间的延长逐渐变大，结合水含量减少，表明抗冻蛋白能够抑制二硫键的断裂和二级结构的变化，减少冰晶的重结晶，防止面团的水分散失，维持面团的持水能力。

Effect of Antifreeze Proteins on Protein Characteristics and Moisture State in Prefermented Frozen Dough

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.