高压处理对热变性米蛋白酶解特性的影响

Effect of High Hydrostatic Pressure Treatment on Enzymolysis Characteristics of Thermo-Denatured Rice Protein

研究高压处理热变性米蛋白在碱性蛋白酶酶解时其溶解性、水解度、—SH含量、分子特征和微观形态的变化特征。结果显示:米蛋白经100～700MPa处理后酶解所得可溶性蛋白的含量均高于未高压处理者,其中500MPa时增加幅度最大,—SH含量也最高。当酶解120min时,高压处理米蛋白可溶性米蛋白的比例达73.0%,而未高压处理米蛋白的可溶性米蛋白只有53.6%,但二者水解度(分别为7.40%和7.05%)的差异并不明显;凝胶过滤色谱分析表明,高压处理后酶解时可溶物的相对分子质量小于未高压处理的酶解物;SDS-PAGE分析表明,高压处理米蛋白不溶性酶解物中大分子组分的含量明显减少,小分子组分明显增加;扫描电镜观察显示,经高压处理的米蛋白形态相对蓬松。因此,适当高压处理有利于米蛋白的酶解,且酶解特性与米蛋白高压处理后的结构变化有直接关系。

Some enzymolysis properties such as solubility, hydrolysis degree, — SH content, molecular characteristics and microcosmic morphology of high hydrostatic pressure （HHP） treated thermal denatured rice protein during hydrolysis with alcalase were investigated. The results showed that the contents of soluble rice protein and free —SH in samples pretreated at high pressure 100-700 MPa were both increased （especially at 500 MPa）, compared with that of untreated samples. The ratio of soluble rice protein in the hydrolysate obtained after HHP treatment at 500 MPa followed by 120 min of hydrolysis was 73. 0% compared with only 53.6% for that obtained for non-HHP treated rice protein. However, no obvious difference in the degree of hydrolysis was found. The gel filtration chromatographic analysis indicated that soluble hydrolysates with lower relative molecular mass were obtained using HHP treatment and subsequent enzymatic hydrolysis compared to direct enzymatic hydrolysis. The SDS-PAGE analysis indicated that the content of high-molecular-mass components in insoluble hydrolysates of HHP treated rice protein decreased notably, while that of low-molecular-mass components increased distinctly. As observed under a scanning electron microscope （SEM）, the morphology of HHP treated rice protein was relatively loose. Therefore, the appropriate HHP treatment was beneficial to the hydrolysis of rice protein and enzymatic hydrolysis characteristics were directly associated with structural changes in rice protein caused by HHP treatment.