限制性酶解对大米蛋白结构、功能特性及体外抗氧化活性的影响

Effects of Restrictive Enzymatic Hydrolysis on the Structural and Functional Properties and in Vitro Antioxidant Activity of Rice Protein

利用胰蛋白酶对大米蛋白进行限制性酶解,得到2%,4%和8%水解度的大米蛋白水解产物,探究不同水解程度对大米蛋白的结构、理化性质及体外活性的影响。结果表明,限制性酶解对大米蛋白的溶解性及乳化性有很大提升,当水解度低于4%时,酶解产物具有良好的热稳定性,然而,随着水解度的增大,其热稳定性呈下降趋势。因酶解作用,大米蛋白中β-转角含量升高,故具有更加舒展的二级结构。其表面呈疏松多孔的微观结构。相比于天然大米蛋白,酶解产物体外抗氧化活性显著提高,而且在高浓度时DPPH和ABTS自由基清除率与同浓度的BHT相当。限制性酶解作为一种温和、安全且高效的改性方法,可有效改善大米蛋白的功能特性,提高其体外抗氧化活性,以丰富大米蛋白资源的应用。

Natural rice protein was modified by enzymatic reaction(trypsin,pH 8.0,55℃)at different times to prepare rice protein hydrolysates with different degrees of hydrolysis(2%,4%and 8%).The effects of different degrees of hydrolysis on the secondary structure,micromorphology,thermal behaviors,intrinsic fluorescence,surface hydrophobicity,sulfhydryl content,solubility,emulsifying properties and in vitro antioxidant activity were investigated.The results showed that the content ofβ-turn in rice protein hydrolysates was increased,indicating a more stretchable and flexible secondary structure.The microstructure was observed to be porous,which is beneficial to improve solubility and emulsifying properties.When the degree of hydrolysis is less than 4%,the hydrolysates exhibited a good thermal stability;as the degree of hydrolysis increased,the heat resistance decreased.The enzymatic process also caused a change in the chromophore content of the protein molecule and a stronger fluorescence intensity as the degree of hydrolysis increased.In addition,the surface hydrophobicity and sulfhydryl content of rice protein decreased first and then increased after enzymatic hydrolysis,which may be related to the folding and unfolding caused by the change of disulfide bond of protein molecule.The study also found that the antioxidant activity of the enzymatic hydrolysates was significantly improved compared with the natural rice protein.The DPPH and ABTS free radical scavenging rate was the same as that of the BHT at the same concentration.As a mild,safe and efficient modification method,restrictive enzymatic hydrolysis can greatly improve the structure and functional properties of rice protein and significantly improve its antioxidant activity in vitro.