酶法水解麦胚蛋白及其产物的抗氧化活性研究

选择碱性蛋白酶、中性蛋白酶、胰酶、木瓜蛋白酶和风味蛋白酶5种蛋白酶对麦胚蛋白进行水解,并考察其水解产物的抗氧化活性。结果表明,中性蛋白酶为制备麦胚抗氧化肽的最适蛋白酶,其最佳水解条件为:底物质量分数4%,酶添加量6 000U/g,酶解温度50℃,pH值7.5,水解至270min时抗氧化活性最大。     

酶法水解丝素的研究

丝素经胰蛋白酶或胰酶水解后 ,产生较多的沉淀 ,而经木瓜蛋白酶、AS1 3 98中性蛋白酶、碱性蛋白酶 Alcalase、复合蛋白酶 Protamex水解后 ,则基本无沉淀生成。比较几种酶对丝素的水解能力 ,其中 Alcalase作用最强。Alcalase对丝素作用的最适 p H为 9左右 ,最适温度为 60℃左右。对丝素的酶解产物进行凝胶过滤色谱 (SEC)分析。     

2种蛋白酶水解牦牛血液蛋白工艺优化

目的 以牦牛血为原料，在碱性蛋白酶水解基础上，加入风味蛋白酶建立复酶分步水解牦牛血液蛋白工艺。方法 以蛋白水解率为指标，运用单因素与正交试验获得碱性蛋白酶水解工艺，在此基础上采用四因素三水平正交试验优化复酶水解pH、水解温度、酶浓度、水解时间，获得碱性蛋白酶与风味蛋白酶分步水解工艺。结果 复酶工艺为在底物浓度1:6 g/mL、最适pH9、最适温度55 ℃、1.00 %的碱性蛋白酶水解1 h后，调节pH到7，添加0.75 %的风味蛋白酶继续水解5 h，可获得最高蛋白水解率为30.77±0.18 %。结论 对研究酶水解牦牛血制备高附加值产品具有重要参考作用。     

酶水解米渣蛋白的工艺研究

采用碱性蛋白酶、中性蛋白酶、菠萝蛋白酶3种酶水解米渣中的大米蛋白,探讨了酶的水解工艺。对3种酶单独使用及复合使用水解米渣的条件和工艺进行了研究,测定了不同条件下的蛋白质浸提度,并确定了最佳的酶复合配比是碱性蛋白酶2709:菠萝蛋白酶为3∶7,酶最适使用量为1000U/ml,在最适酶解温度50℃条件下,水解16h可获得最适蛋白质浸提度。     

酶法钝化大豆胰蛋白酶抑制剂的研究

采用中性蛋白酶、碱性蛋白酶、酸性蛋白酶和木瓜蛋白酶，在其最适pH值和最适温度下水解低温脱脂豆粕1h，分别检测水解前后胰蛋白酶抑制剂活性的变化。结果表明，4种酶都可在不同程度上降解大豆胰蛋白酶抑制剂，但降解程度差异较大，碱性蛋白酶降解作用显著优于其它酶。按照四种酶水解胰蛋白酶抑制剂相对活力的大小排序为：碱性蛋白酶＞酸性蛋白酶＞中性蛋白酶＞木瓜蛋白酶。     

单酶水解羊骨粉效果比较及水解指标相关性分析

以羊骨粉为底物,对7种蛋白酶的水解效果进行比较并对4种水解指标进行相关性分析,确定制备羊骨胶原肽的最佳用酶及最优指标,为生产实际提供参考,有利于羊骨的高值利用及养羊产业链的延伸。各种蛋白酶在单因素试验所确定的较优条件下水解,结果表明碱性蛋白酶效果最好,其次为复合蛋白酶和风味蛋白酶,这3种酶的水解度、短肽得率、多肽生成量及氨基态氮均显著高于其他4种酶。各指标间的相关性分析结果表明,所有蛋白酶的短肽得率与水解度之间的相关性最强,r值位于0.926~0.983之间,且4个指标间均呈极显著相关(P0.01)。对于水解度和短肽得率较低的胃蛋白酶、胰蛋白酶和木瓜蛋白酶,多肽生成量和氨基态氮得率之间r0.90。所以水解羊骨粉,制备胶原肽时,碱性蛋白酶、复合蛋白酶和风味蛋白酶是最适工具酶,水解度或短肽得率是判断水解程度的最优指标。     

牛排菇多肽的酶解工艺优化

以珍稀食用菌——牛排菇为原料,利用单因素试验和响应面法建立其多肽的酶解工艺。以水解度为指标,分别以5 种蛋白酶：酸性蛋白酶、碱性蛋白酶、胰酶、胃蛋白酶、木瓜蛋白酶,对牛排菇进行酶解;考察不同反应时间、底物浓度、pH 值、温度、加酶量对牛排菇多肽提取过程中水解度的影响,并结合响应面试验优化工艺条件。结果显示：胰酶为酶解牛排菇多肽的最适蛋白酶,当酶解时间5 h、底物浓度5%、pH8、加酶量10 000 U/g、酶解温度45 ℃时,牛排菇多肽的水解度为59.17%,且蛋白质含量可达33.67%。     

草鱼消化道粗蛋白酶的部分性质

用丙酮脱脂然后用磷酸盐缓冲溶液从草鱼肠道中提取一种主要含有酸性蛋白酶和碱性蛋白酶的粗蛋白酶。该粗酶水解血红蛋白的最适pH=3～4，水解酪蛋白的最适pH值有2个，分别为pH4．4和PH10．3。水解牛血红蛋白的最适作用温度为37℃，水解酪蛋白的最适作用温度为45℃。酸性蛋白酶在50℃保温30min后只有大约20％的最初活性被保留，而要使碱性蛋白酶丧失80％的最初活力需要在60℃保温30min。     

碱性蛋白酶水解鸡蛋清制备活性多肽

以新鲜鸡蛋清为原料,利用碱性蛋白酶水解法制备活性多肽,并对影响碱性蛋白酶水解过程的各个因素进行研究。通过测定蛋清酶解液氨基态氮含量,确定碱性蛋白酶水解蛋清制备活性多肽的最适pH为7.0,最适温度为70℃,酶与底物浓度比[E/S]1 000 IU/g,最适底物浓度为70%,水解时间5 h。在此水解条件下,酶解液氨基态氮含量达到1 491.20 mg/kg。     

蛋白酶水解豆渣制备大豆肽的研究

以大豆豆渣为原料,分别采用木瓜蛋白酶、碱性蛋白酶、中性蛋白酶对大豆豆渣进行水解制备大豆肽.研究了3种蛋白酶在不同温度、pH值、水解时间、酶浓度下水解大豆豆渣的最适酶反应条件,以及水解产物对酸豆乳发酵的影响.结果得出,实验豆渣蛋白质含量为10.4 g/(100 g);木瓜蛋白酶的最适水解条件是底物质量分数5％,酶浓度20 000 U/g,水解温度为50℃,pH7,水解6h,最大水解度可达87.31％;碱性蛋白酶的最适水解条件是底物质量分数5％,酶浓度15 000 U/g,水解温度为55℃,pH9,水解3h,最大水解度可达91.23％;中性蛋白酶的最适水解条件是底物质量分数5％,酶浓度15 000 U/g,水解温度为45℃,pH7,水解8h后达到最大水解度,最大水解度可达81.42％.     

猪胰脏中胰酶的提取工艺优化研究

目的：采用异丙醇为提取剂,一种新型沉淀剂壳聚糖对猪胰脏中胰酶的制备工艺进行研究。方法：通过单因素试验和正交试验,对影响胰酶收率和活力的因素(异丙醇浓度、提取时间、pH 值、壳聚糖用量)进行研究,确定最佳工艺条件。结果：所得的最佳工艺条件为异丙醇浓度7.5%、提取时间6h、pH4、壳聚糖用量0.1%。结论：所制得的胰酶收率为12.19%,胰蛋白酶、胰淀粉酶和胰脂肪酶的酶活分别为4836、14320、20580U/g,说明壳聚糖有很好的沉淀絮凝效果。     

Lycopene extraction from extruded products containing tomato skin

To determine the lycopene content of extruded products containing 10% tomato skin, the conditions for solvent extraction were optimised. After three extraction cycles at 50 °C each for 15 min at a solvent to meal ratio of 40:1, a maximum of 6.6 ppm lycopene was extracted. However, the extraction was considered incomplete, thus the product was digested by pancreatin prior to extraction. The extracted lycopene content was increased to 23.5 ppm using the optimum conditions of 20 min of digestion with 10 mg mL^?1 pancreatin. To validate the extraction efficiency at optimum conditions, a set of extruded products containing different lycopene concentrations was used. Digestion increased the extracted lycopene content by more than 2.5‐fold between the products. Furthermore, this inclusion significantly improved the correlation coefficient between the red colour and the extracted lycopene content. Therefore, including a digestion step prior to extraction by solvents was necessary to efficiently extract lycopene from extruded products.     

酶法水解荞麦球蛋白制备抗氧化活性肽的研究

分别采用3 种蛋白酶水解荞麦球蛋白,以酶解液水解度和对O2·的清除率为指标,研究酶解荞麦球蛋白的最佳工艺。并进一步对酶解产物进行Sephadex G-25 凝胶柱层析分离,然后对其各分离组分清除O2·、·OH 和DPPH·的能力及分子量分布进行研究。结果显示：采用碱性蛋白酶水解荞麦球蛋白效果优于胰蛋白酶和木瓜蛋白酶,最佳酶解工艺条件为：加酶量20000U/g,温度55℃,pH9,底物浓度5%,反应时间2h;经柱层析分离得到的分子量小于1000D 的组分Ⅲ显示了较强的抗氧化能力。其清除O2·、·OH 与DPPH·的IC50 分别为0.75、0.897、0.38mg/ml,高于分子量较大的组分Ⅰ和未经分离的荞麦球蛋白酶解液。     

利用酶法促使骨粉中钙转化的研究

利用中性蛋白酶,胰酶和碱性蛋白酶作用于骨粉,胰酶可获得最大钙转化率。研究表明,骨粉中钙溶出率为２．５６％,骨钙转化率为１６．０％,并且确定胰酶最佳用量为骨粉：胰酶（ｗ／ｗ）＝１０００：１－２０００：１,最佳酶解时间为９－１０ｈ。     

Disulfide Reduction and Molecular Dissociation Improves the Proteolysis of Soy Glycinin by Pancreatin in vitro

THE EFFECTS of structural modification by urea and dithiothreitol on the in vitro pancreatin proteolysis of soy glycinin was studied. Urea, up to 4.5M, which causes dissociation of glycinin into subunits and some unfolding of the polypeptides progressively increased proteolysis by pancreatin as measured by the pH-stat method. Reduction of the intermolecular disulfide bonds with dithiothreitol doubled the rate of proteolysis and when additional intramolecular disulfide bonds of glycinin were cleaved, the rate of digestibility increased approximately threefold becoming equivalent to casein in its susceptibility to proteolysis by pancreatin.     

Evaluation of leaf protein isolates of some Egyptian crops

Thein vitro digestibilities by pepsin, pancreatin and pepsin followed by pancreatin of the leaf protein isolates of four species of Egyptian crops were studied. Bean and cabbage leaf protein isolates were more digestible with pepsin and pancreatin, each used individually, as well as with pepsin followed by pancreatin, than those of tomato and sugar cane. There were only minor variations in the amino acids content of the different leaf protein isolates with the sulphur-containing amino acids being the limiting acids.Bean and cabbage leaf protein isolates were superior to those of tomato and sugar cane from the point of view of availability of amino acids.     

The effect of lactic acid bacteria fermentation on the antioxidant activity of wheat gluten pancreatin hydrolysates

The antioxidant activities of the fermented wheat gluten hydrolysates with different fermentation times were investigated to elucidate the impact of lactic acid bacteria (LAB) fermentation on the wheat gluten hydrolysates. Prior to LAB fermentation, wheat gluten was deamidated by hydrochloric acid and then hydrolysed by pancreatin to 12 and 24 h, respectively. Results showed that LAB fermentation had significant impacts on the enzymatic efficiency and antioxidant activities of wheat gluten. The degree of hydrolysis and protein recovery of hydrolysates gradually increased and then reached maximum values, respectively, when fermenting with LAB for 36 h. The hydrolysis degree and protein recovery of fermented pancreatin 24‐h hydrolysates were larger than that of the fermented pancreatin 12‐h hydrolysates during the whole fermentation. The antioxidant activity analysis revealed a marked increase and improvement in the scavenging activities of 1,1‐Diphenyl‐2‐picrylhydrazyl·radicals, hydroxyl radicals and oxygen radical absorbance capacity, while the scavenging activities of ABTS⁺ radical decreased as the fermentation time extended. The antioxidant activities of pancreatin 24‐h hydrolysates were higher than that of the pancreatin 12‐h hydrolysates during the whole LAB fermentation.     

Comparison of ACE inhibitory and DPPH radical scavenging activities of fish muscle hydrolysates

To utilise Atlantic salmon, Coho salmon, Alaska pollack, and southern blue whiting as components of neutraceutical food and to clarify the potential physiological function of those fishes, their muscles were hydrolysed with pepsin, pancreatin or thermolysin. Methanolic extracts of fish muscle and their hydrolysates were prepared for analysis of angiotensin converting enzyme (ACE) inhibitory and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities. Pepsin hydrolysates of all the fish samples did not increase degree of hydrolysis, extractive nitrogen content and bioactivities. Pancreatin and thermolysin improved the ACE inhibitory activity, and the activity was expressed following the peak of size exclusion chromatography (SEC). The DPPH radical scavenging activity was increased following pancreatin and thermolysin hydrolysis, but this activity was not related to the SEC result. Except for the lower DPPH radical scavenging activity of Alaska pollack pancreatin hydrolysate than those of the others, there was no significant difference in the ACE inhibitory and DPPH radical scavenging activities by fish species.