胞壁蛋白酶(CEP)酶解对酪蛋白结构及功能特性的影响

Effects of Enzymatic Hydrolysis with Cell Wall Proteinase(CEP) on Structural and Functional Properties of Casein

通过纳米粒度分析、傅立叶红外光谱(FT-IR)、乳化性、乳化稳定性、蛋白溶解性、抗氧化性及ACE抑制率的测定,分析探讨酪蛋白及其不同水解度(DH 2.4%、4.5%、7.1%、8.3%)的嗜酸乳杆菌胞壁蛋白酶(CEP)酶解产物的结构及功能特性。FTIR分析表明CEP酶解改变了酪蛋白各种构象所占的比例,酪蛋白二级结构发生了不同程度的变化;纳米粒度分析表明酪蛋白颗粒大小随水解的加深先减小后增大,其水解物颗粒在DH 4.5%时最小,乳化稳定性最大;酪蛋白的乳化性随水解的加深先增大后减小,DH7.1%时增至最大,与其溶解性的变化趋势一致;此外酪蛋白的酶解物具有一定的ACE抑制活性及抗氧化性,且DPPH清除能力在一定范围内随水解度及浓度的增大而增大,当DH为8.3%,浓度为5 mg/mL时,DPPH清除能力增大至35.00%。因此CEP酶解可有效改善酪蛋白的结构及功能特性,为乳源性功能多肽的开发提供理论依据。

The structural characteristics of casein hydrolyzed by cell wall proteinase （CEP） from Lactobacillus acidophilus were analyzed by granularity and Fourier transform infrared spectroscopy （FTIR）. The effects of different degree of hydrolysis （DH 2.4%, 4.5%, 7.1% and 8.3%） on functional properties of casein were determined by emulsibility, emulsion stability, solubility, antioxidant activity and ACE inhibitory activity. The results of FTIR spectra indicated remarkable changes in the chemical compositions and macromolecular conformation of casein after hydrolysis. The secondary structure of casein was changed with the enzymatic treatment. The nanoparticle size analysis showed that the casein particles decreased during the initial hydrolysis time （DH〈4.5%）, but increased for further hydrolysis, which resulted in the highest emulsion stability under DH 4.5%. The emulsibility and solubility of casein first increased and reached the highest when DH was 7.1%, and then decreased with the further hydrolysis. In addition, the casein hydrolysates had certain ACE inhibitory activity and antioxidant properties, and the DPPH removal capacity within a certain range increased as DH and concentration increased. The highest DPPH removal capacity was 35.00% with DH 8.3% and hydrolysates concentration of 5 mg/mL. Therefore, the enzymatic hydrolysis with CEP can effectively improve the structural and functional properties of casein. This research will provide useful theoretical basis for the production of ACE inhibitory peptides derived from casein.