论文标题:酶解乳清蛋白制备ACE抑制肽的研究
Preparation of Angiotensin Ⅰ Converting Enzyme Inhibitory Peptides from Whey Protein by Protease Hydrolysis
论文作者 李朝慧
论文导师 罗永康,论文学位 硕士,论文专业 食品科学与工程
论文单位 中国农业大学,点击次数 108,论文页数 57页File Size2162k
2005-05-01论文网 http://www.lw23.com/lunwen_32455732/ 乳清蛋白;酶解;ACE抑制肽;超滤;脱盐
Whey protein; enzymatic hydrolysis; ACE inhibitory peptides; Ultrafilitration;Desalinization
血管紧张素转换酶(Angiotensin-Ⅰ-converting enzyme,ACE)抑制剂具有降血压的作用,本文利用酶解法从乳清蛋白中制备ACE抑制肽。 改进并建立了可靠的ACE抑制率的体外检测方法,该方法具有良好的精确性和重现性,可以用于各种样品的ACE抑制率的检测。 以ACE抑制率为指标,从几种蛋白酶中筛选出碱性蛋白酶为制备ACE抑制肽的最佳用酶。采用三因素二次正交旋转设计,以ACE抑制率和水解度为指标,对碱性蛋白酶水解乳清蛋白的条件进行了优化,得出碱性蛋白酶制备ACE抑制肽的最优条件为:水解温度50℃,底物浓度为5%,E:S为5.5%,通过单因素试验确定了最适水解时间为6h,在此条件下获得水解物的IC_(50)值为0.97m/mL。同时发现水解度和ACE抑制率之间没有相关性。 利用6KDa超滤膜通过超滤对ACE抑制肽进行分离,确定了其工艺参数温度为20℃,压力为0.1MPa,在此条件下进行超滤,透过液和截留液的ACE抑制率分别提高了34%和19.58%,由此可见使用6KDa超滤膜可以有效的分离ACE抑制肽。 采用离子交换树脂对ACE抑制肽进行脱盐处理,以50r/min的流速过阳离子交换树脂柱,脱盐率达到80%,氮的回收率达到90%,而水解物的ACE抑制率几乎没有什么变化,说明酶解乳清蛋白制备ACE抑制肽时用阳离子交换树脂脱盐是可行的。 初步建立了生产ACE抑制肽的最佳工艺流程:乳清蛋白→水化→蛋白酶水解→水解液→离子交换树脂脱盐→冷冻干燥→产品,该工艺直接对水解物进行脱盐可以缩短生产ACE抑制肽的工艺步骤,减少蛋白质的损失,而且水解物的ACE抑制率也较高,符合工业化生产的要求。
Angiotensin-1 -converting enzyme(ACE) plays an important physiological role in regulating blood pressure. ACE converts an inactive form of decapeptide, angiotensin I , to a potent asoconstrictor, octapeptide angiotensin II, and inactivates bradykinin, which has a depressor action. Currently, many ACE inhibitors have been used as antihypertensive agents. In the present study, the ACE inhibitory peptides were prepared from whey protein with protease hydrolysis.A reliable assay method of ACE inhibitory peptides with high accurance and repeatability was modified and established, and it can be used to determine the ACE inhibitory activities of all kinds of samples.Taking ACE inhibitory activity as index, after screening of several commercial proteases, alcalase was used to hydrolyze whey for production of ACE inhibitory peptide.Taking ACE inhibitory activity and the degree of hydrolysis as indexes, orthogonal rotational regression design was used to optimize the hydrolysis conditions of whey protein with alcalase. The optimal hydrolysis conditions of whey were: temperature 50℃, substrate concentration 5%, enzyme to substrate ratio 5.5%, hydrolysis time 6 hours. In these conditions, whey hydrolysates IC_(50) was 0.97mg/mL,Ultrafiltration was applied to isolated ACE inhibitory peptides.The optimal ultrafiltration condition for 6KDa membrance was at 20°C with pressure 0.1 MPa. After ultrafiltration the ACE inhibitory activities of the permeates and potentates separately increased 34% and 19.58%.Salt was removed by ion exchange resin at a flow rate of 50r/min with desalinization rate of approximate 80% and nitrogen recovery rate of 90%. No differences were observed on the ACE inhibitory activity of samples.An optimum processing technology of ACE inhibitory peptides was established as : whey→hydrating→protease hydrolysis→hydrolysate →desalinization by ion exchange resin→freeze drying→ACE inhibitory peptides. In this processing technology, high ACE inhibitory activities and low protein loss were obtained with direct desalinization of whey hydrolysates.
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