Wheat germ protein hydrolysate prepared by enzymatic hydrolysis was separated with ultra-filtration membranes with a molecular weight cutoff （MWCO） of 3 ku and 6 ku, respectively. Four ultra-filtration parameters such as pressure, time, pH and sample concentration were optimized by response surface methodology to be 0.08 MPa, 23 min, 6.83 and 2%, respectively. Under these conditions, the ultra-filtration membrane flux of was 4.85 L/（m^2 ·h）. The obtained fraction of less than 3 ku in molecular weight exhibited a DPPH free radical scavenging rate of 78.93% at the concentration of 11%.%采用3ku和6ku的超滤膜对麦胚多肽进行分级分离，考察3种分离产物对DPPH·的清除能力，发现分子质量在3ku以下的麦胚多肽对DPPH·的清除率可达75．32％，高于其他分离产物。采用响应面试验方法对麦胚多肽的超滤条件进行优化试验，结果表明，最佳超滤条件为超滤压力0．08MPa、超滤时间23min、超滤pH6．83、溶液质量分数2％，此时膜通量为4．85L／（m^2．h）。所得分子质量小于3ku的麦胚多肽在质量分数11％时，其DPPH·清除率为78．93％。超滤法精制的麦胚多肽具有良好的DPPH·的清除能
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