鸡蛋清卵白蛋白酶解工艺优化及其结构性质

研究鸡蛋清卵白蛋白的酶解工艺及其结构性质，以水解度为指标，确定最佳酶源为碱性蛋白酶，其水解度为26.55%，显著优于其他蛋白酶（P＜0.05）。以碱性蛋白酶酶解鸡蛋清卵白蛋白，采用单因素和五元二次正交旋转试验研究酶解工艺；针对酶解前后卵白蛋白的功能特性进行分析，并采用紫外扫描、傅里叶红外变换光谱、差示扫描量热针对卵白蛋白及其酶解产物进行结构表征。结果发现，碱性蛋白酶酶解鸡蛋清卵白蛋白最佳工艺条件为反应温度52.5 ℃、反应时间5 h、pH 8.25、酶用量5 500 U/g、底物添加量5%，此条件下水解度为27.88%。酶解后产物表面巯基含量降低了3.6 mol/（L·g），溶解度大幅度提高，起泡性降低了18.18%，泡沫稳定性降低了20.24%，乳化活性指数升高了13.56 m2/g，乳化稳定性提高了10.46%。同时，酶解后的卵白蛋白肽链发生了裂解，有序的二级结构被破坏，暴露出更多氨基酸残基，α-螺旋略有减少，β-转角相应增加，亲水基团也相应的增加。

Enzymatic Hydrolysis and Structural Properties of Egg White Ovalbumin

The enzymatic hydrolysis of egg white albumin and changes in its structural properties were studied. As
evaluated in terms of degree of hydrolysis (DH), alkaline protease was determined as the best enzyme to hydrolyze egg
white albumin, which was significantly superior to other proteases tested, providing a DH value of 26.55% (P < 0.05). The
enzymatic hydrolysis process was studied through single factor and quadratic general rotary unitized design experiments.
The structural properties of egg white albumin and its hydrolysate were characterized by ultraviolet (UV), Fourier transform
infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). The results showed that the optimum hydrolysis
conditions were as follows: hydrolysis temperature, 52.5 ℃; hydrolysis time, 5 h; pH, 8.25; enzyme dosage, 5 500 U/g;
and substrate concentration, 5%. Under these conditions, the maximum DH value of 27.88% was obtained. The resulting
hydrosulfuryl content showed a decrease of 3.6 mol/(L·g) in surface hydrosulfuryl, a significant increase in solubility, a
decrease of 18.18% in foaming ability, and a reduction of 20.24% in foam stability as compared to egg white albumin. Moreover,
the emulsifying index and emulsion stability of the hydrolysate increased by 13.56 m2/g and 10.46%, respectively. At the same
time, the enzymatic hydrolysis led to peptide chain cleavage of egg albumin, damage to the ordered secondary structure, exposure
of more amino acid residues, slight decrease in α-helix, and corresponding increases in β-turns and hydrophilic groups.