低盐和高盐条件下L-组氨酸对肌原纤维蛋白结构及体外消化特性的影响

Effect of L-Histidine on Structural Characteristics and in Vitro Digestibility of Myofibrillar Protein at Low and High Salt Concentrations

研究低盐(0.2 mol/L NaCl)及高盐(0.6 mol/L NaCl)条件下L-组氨酸(L-histidine,His)添加量(0、0.2、0.4 g/100 mL)对猪肉肌原纤维蛋白(myofibrillar protein,MP)结构及体外消化特性的影响。结果表明:在低盐和高盐条件下,His的添加均引起MP发生解折叠,使其分子构象发生转变,α-螺旋结构含量降低,并伴随其他二级结构(β-折叠、β-转角、无规则卷曲)含量的增加;同时暴露出埋藏在蛋白分子内部的疏水基团,表面疏水性增加;随着His添加量的升高,MP的α-螺旋结构含量显著下降(P<0.05),表面疏水性显著升高(P<0.05);体外消化结果表明,His的添加使得MP体外消化率显著提高(P<0.05),酶解产物粒径显著降低(P<0.05)。因此,在低盐或高盐条件下,His的添加可引起MP结构发生解折叠,暴露出更多酶切位点,进而促进胃蛋白酶和胰蛋白酶对MP的酶解作用,从而提高MP消化率。

The effect of L-histidine(His)(0,0.2,0.4 g/100 mL)on the structural characteristics and in vitro digestibility of pork myofibrillar protein(MP)was studied at low(0.2 mol/L NaCl)and high(0.6 mol/L NaCl)salt concentrations.The results showed that addition of His caused the unfolding of MP and the transformation of its molecular conformation at both low and high salt concentrations.The content ofα-helical structure decreased,accompanied by an increase in the contents of other secondary structures(β-sheet,β-turn,random coil).Meanwhile,addition of His caused the exposure of the buried hydrophobic groups,resulting in increased surface hydrophobicity of MP.In addition,the content ofα-helical structure of MP decreased(P<0.05),and the surface hydrophobicity increased(P<0.05)with increasing His concentration.The results of in vitro digestion showed that the addition of His significantly improved the in vitro digestibility of MP(P<0.05)and reduced the particle size of the enzymatic hydrolysate(P<0.05)regardless of salt concentration.Therefore,it could be concluded that His addition caused the unfolding of MP structure,resulting in the exposure of more enzymatic cleavage sites,facilitating the enzymatic hydrolysis of MP by pepsin and trypsin,thus improving the digestibility of MP.