鸡骨酶解物的抗氧化活性研究

分别选用复合风味蛋白酶、Protamex复合蛋白酶、Alcalase蛋白酶、胰酶、胰蛋白酶、AS.1398中性蛋白酶和木瓜蛋白酶水解鸡骨泥,研究鸡骨酶解物(蛋白质含量3 mg/mL)对DPPH、羟自由基(OH·)的清除能力及其还原性.试验结果表明:Protamex复合蛋白酶酶解鸡骨产物的DPPH清除率最强,即81.44%;复合风味蛋白酶酶解物OH·清除率达30.32%,还原性测定的吸光值为0.3.总之,鸡骨酶解物的DPPH清除能力强于羟自由基清除能力和还原力.在研究不同浓度和水解度对鸡骨酶解物清除DPPH活性的影响时发现,随着酶解物蛋白质质量浓度的增大,酶解物的DPPH清除率升高.复合风味蛋白酶、Protamex复合蛋白酶的鸡骨酶解物蛋白质质量浓度分别为4、6mg/mL时,其DPPH清除率分别达91.49%、97.3%.但DPPH清除率与水解度不呈正相关性,只有在特定水解度下,使抗氧化肽含量最高时,水解物才表现出最强的抗氧化能力.例如复合风味蛋白酶、AS.1398中性蛋白酶、Protamex复合蛋白酶、胰酶的最佳水解度分别为12.59%、23.78%、14.45%、20.04%.     

鸡蛋壳膜多肽酶解工艺及抗氧化活性研究

试验以鸡蛋壳膜为原料,通过酶解法制备小分子肽,并对其生物活性进行研究。以水解度为评价指标,通过单因素试验确定蛋白酶种类、酶解时间、料液比以及酶添加量等因素对壳膜多肽水解度的影响,并通过响应面设计（Box-Behnken design,BBD）对酶解条件进行三因素三水平优化;通过高效凝胶过滤色谱测定酶解后壳膜多肽分子量的分布情况,并测定壳膜多肽对DPPH·、ABTS+·、·OH、O2-·的清除能力。结果表明,最佳酶解工艺条件为碱性蛋白酶（AP-200a）,酶添加量2.4%,料液比1∶9.5（g/mL）,酶解时间5 h;在此条件下,壳膜多肽水解度为27.15%,水解后相对分子质量小于1 000 Da的小分子肽所占比例为90.9%;且壳膜多肽对DPPH·、ABTS+·的清除率分别为（93.03±0.51）%、（94.53±0.92）%,与 VC的效果相当;但对·OH 和 O2-·的清除率分别为（43.33±1.10）%和（53.40±0.70）%。因此,通过该法酶解得到的壳膜多肽中小分子肽占比较高,易被人体消化吸收,且具有一定抗氧化活性。     

球磨辅助酶解制备南瓜籽ACE抑制肽

以南瓜籽蛋白为原料,通过球磨预处理辅助酶解法制备血管紧张素转换酶（ACE）抑制肽。以ACE抑制率和水解度为评价指标,对蛋白酶进行筛选。采用单因素试验研究球磨时间、酶解时间、底物质量浓度、pH和酶解温度对酶解产物ACE抑制率和水解度的影响,在此基础上,以ACE抑制率为考察指标,采用响应面法对球磨辅助酶解工艺条件进行优化。结果表明：球磨预处理可显著提高南瓜籽蛋白的酶解效率;最佳球磨辅助酶解工艺条件为选用碱性蛋白酶、球磨时间6 min、酶解时间10 h、底物质量浓度0.08 g/mL、pH 8.5、酶解温度55 ℃,在此条件下所得ACE抑制肽的ACE抑制率可达(86.65±0.55)%。     

鲤鱼鳞酶解工艺优化及酶解液抗氧化活性研究

为得到高抗氧化活性的鲤鱼鳞胶原蛋白酶解液,试验以羟基自由基（·OH）和超氧阴离子自由基（O2-·）清除率作为主要检测指标,通过单因素试验研究酶解温度、pH值、加酶量、底物浓度、酶解时间对鱼鳞胶原蛋白酶解液抗氧化活性和水解度的影响。在此基础上,采用响应面分析法对酶解工艺条件进行优化。得到试验最优工艺为酶解时间4.4 h,酶解温度66.0℃,pH8.5,底物浓度20 mg/mL,加酶量4%。在此条件下,酶解液的·OH清除率为80.24%,O2-·清除率为65.34%,亚铁离子（Fe2＋）螯合能力为59.73%。对比常用抗氧化剂,在O2-·清除能力方面,酶解液效果低于丁基羟基茴香醚（butylated hydroxyanisole,BHA）和抗坏血酸（P＜0.05）,但在·OH清除能力方面,酶解液已达到BHA和抗坏血酸的水平（P＞0.05）,在Fe2＋螯合能力方面,酶解液显著优于BHA和抗坏血酸（P＜0.05）。     

玛咖多肽的制备及抗氧化活性研究

以水解度为考察指标,在单因素实验基础上,利用正交实验优化酶解玛咖粗蛋白制备玛咖多肽的工艺,同时通过·OH、DPPH·及O₂-·清除实验研究提取过程中产生的玛咖醇提液以及在最适条件下制得的玛咖多肽的抗氧化活性,并对玛咖多肽进行氨基酸组成分析。结果表明,酶解玛咖粗蛋白的最适酶是碱性蛋白酶,酶解制备玛咖多肽的最适条件是酶解时间4 h、酶解pH为10.5、酶解温度55℃、加酶量1.6×104 U/g,在此条件下,玛咖粗蛋白的水解度为(31.55%±0.74%)。稀释一倍的玛咖醇提液对各自由基清除率为最大,对DPPH自由基的清除率为94.44%,对·OH的清除率为85.05%,对O₂-·清除率为53.85%。玛咖多肽对·OH、DPPH·及O₂-·的IC₅₀值分别为0.85、0.44、0.86 mg/mL,且表现出一定的量效关系。另外,玛咖多肽中Tyr、His、Lys、Pro四种氨基酸含量为16.98%,其氨基酸组成与抗氧化活性存在一定关系。该结果说明玛咖醇提液及玛咖蛋白均具有一定的抗氧化活性。     

仿刺参精酶解工艺条件优化及体外抗氧化

本研究以仿刺参精(Apostichopus japonicus spermary,ASJS)为材料,以水解度为指标优化了酶解工艺条件,并考察了酶解产物的体外抗氧化效果。实验选用木瓜蛋白酶(PAP)、复合蛋白酶(PRO)和风味蛋白酶(FLA)作为实验用酶,以双缩脲法结合三氯乙酸法测定水解度,通过单因素与正交实验,优化了单酶酶解工艺条件,并与双酶及三酶复配水解进行了比较实验,最后对不同的水解产物进行了体外抗氧化活性测定。结果表明:单酶最佳酶解工艺条件为PAP:酶添加量3.0%、温度70℃及反应时间4 h;PRO:酶添加量3.0%、温度45℃及反应时间4 h;FLA为:酶添加量2.0%、温度45℃及反应时间4 h。在最佳酶解工艺条件下PAP水解度为32.14%,PRO为31.09%,FLA为11.89%。双酶及三酶的复配水解工艺检测到的水解度均低于单PAP及单PRO。不同水解产物清除羟自由基和超氧阴离子自由基能力结果为,在样品浓度为5 mg/m L和10 mg/m L时,ASJS的PAP酶解产物好于PRO、FLA、双酶、三酶复配,同时也好于仿刺参卵及体壁PAP酶解产物。综上可知,ASJS的PAP水解产物显示出较好的体外抗氧化活性,可以进一步开发利用。     

具α-葡萄糖苷酶抑制作用的蚕豆蛋白酶解物的制备

以蚕豆为原料,通过碱溶酸沉法得到蚕豆蛋白,再通过酶解制备具有α-葡萄糖苷酶抑制作用的蚕豆蛋白酶解物。以α-葡萄糖苷酶抑制率与水解度为指标,考察蛋白酶种类、酶解温度、酶解pH、料液比、加酶量与酶解时间对蚕豆蛋白酶解的影响,在此基础上采用响应面法对工艺参数进行优化。结果表明：酶解蚕豆蛋白制备具有α-葡萄糖苷酶抑制作用酶解物的最优工艺条件为以碱性蛋白酶为最适用酶、酶解温度50 ℃、酶解pH 8.5、酶解时间4.3 h、料液比1∶ 10、加酶量14 000 U/g,在此条件下酶解物α-葡萄糖苷酶抑制率为（38.58±0.87）%,蛋白水解度为22.87%。     

酶解虾壳蛋白制备ACE 抑制剂的工艺优化

以虾壳粉为原料,以水解度和ACE抑制率为指标,利用中性蛋白酶、碱性蛋白酶、菠萝蛋白酶和木瓜蛋白酶进行酶解,其中中性蛋白酶和碱性蛋白酶有较高的ACE抑制活性,因此对碱性蛋白酶和中性蛋白酶的工艺条件进一步优化。结果表明：碱性蛋白酶酶解工艺优化条件为：温度60℃、pH9.5、底物质量浓度2.5g/100mL、加酶量4000U/g、酶解时间2.5h,在此条件下ACE抑制率最高,为67.70%,水解度为69.79%;中性蛋白酶酶解工艺优化条件为：温度50℃、pH7.0、底物质量浓度2.5g/100mL、加酶量2000U/g、酶解时间2h,在此条件下ACE抑制率最高,为84.04%,水解度为26.76%。提示中性蛋白酶酶解能够产生更多的ACE抑制肽,是酶解虾壳蛋白制备ACE抑制肽的较优酶。     

消化道酶连续水解制备苦荞球蛋白多肽及其抗氧化活性研究

采用胃蛋白酶、胰蛋白酶对苦荞球蛋白进行连续水解,以水解度(DH%)为指标,采用单因素分析底物浓度、酶底比、pH值、水解时间对苦荞球蛋白的酶解效果,并通过正交实验对胃-胰蛋白酶连续作用的酶解工艺进行优化;检测酶解产物的体外抗氧化活性。结果表明:苦荞球蛋白经胃蛋白酶酶解的最佳条件为:底物浓度30 g/L、酶底比为10%、pH值为2.0、反应时间为2.0 h;胰蛋白酶酶解的最佳条件为:底物浓度30 g/L、酶底比为5%、pH值为8、反应时间为2.5 h;胃-胰蛋白酶连续酶解最佳条件:经胃蛋白酶先水解1 h后再继续用胰蛋白酶水解1.5h,水解度为25.18%。和苦荞球蛋白相比,苦荞球蛋白酶解物的抗超氧阴离子能力及羟自由基清除能力均增强(p0.05)。     

长白山松子降血压肽制备工艺优化

采用碱性蛋白酶对长白山松子分离蛋白进行酶解,以水解度和酶解物的ACE抑制率为考察指标,考察酶解p H、酶解温度、底物浓度、加酶量4个因素的影响,通过响应面(Box-Benhnken)组合优化试验,确定得到ACE抑制率最佳的条件为酶解p H8.9,酶解温度55℃,加酶量7 500 U/g(以底物计),底物浓度2.5%,此时ACE抑制率为70.1%,水解度为17.5%,与模型预测值基本相符。     

Co-precipitation of whey and pea protein – indication of interactions

The aim was to optimise the yield of co-precipitation of whey protein isolate (WPI) and pea protein isolate (PPI) and compare co-precipitates and protein blends with respect to solubility. The yield of co-precipitates was tested with different protein ratios of WPI and PPI in combination with different temperatures and acid precipitation (pH 4.6). The highest precipitation yield was obtained at protein ratios WPI < PPI, high temperature and alkaline protein solvation. The solubility was measured by an instability index and absorption spectroscopy of re-suspended precipitated proteins at pH 3, 7 and 11.5. Co-precipitates had significantly lower solubility than protein blends. Protein ratios WPI > PPI, low precipitation temperature and high pH showed the highest solubility. Differences in protein composition between co-precipitates and protein blends were observed with SDS-PAGE and matrix-assisted laser desorption ionisation time-of-flight, and indicated different protein–protein interaction in samples, which needs further investigations.     

Interaction and Functionality of Mixed Myofibrillar and Enzyme-hydrolyzed Soy Proteins

ABSTRACT Native and briefly heated (85 °C for 3 min) soy protein isolates (SPI) were partially hydrolyzed (4% DH) by Alcalase® and Flavourzyme™ before incorporation into a pork myofibril isolate (MPI) system. The hydrolysis of soy protein enhanced its interaction with MPI, leading to a decreased thermal stability of both soy and muscle proteins. Alcalase SPI hydrolysates, when compared with nonhydrolyzed SPI, improved viscoelastic properties and hardness of MPI gels, while Flavourzyme SPI hydrolysates had an adverse effect. Hydrolyzed SPI augmented emulsifying properties of MPI; the specific efficacy depended upon the type of enzymes used, the SPI:MPI ratio, and whether SPI was heated before hydrolysis.     

大豆蛋白生产与应用现状

该文综述大豆蛋白制品—大豆蛋白粉、大豆分离蛋白、大豆浓缩蛋白、大豆组织蛋白生产现状、存在问题及大豆蛋白在面制品、肉制品、乳制品、饮料制品等中应用现状。     

The structures and functions of ice crystal-controlling proteins from bacteria

Many organisms have evolved into unique mechanisms which minimize freezing injury due to extracellular ice formation. Specifically, certain bacteria have produced a few proteins each with different functions. For example, the ice nucleation protein acts as a template for ice formation, which is responsible for imparting ice nucleating activity. The anti-nucleating protein inhibits the fluctuation of ice nucleus formation by a foreign particle in the water drop. Also, the antifreeze proteins depress the freezing temperature, modify or suppress ice crystal growth, inhibit ice recrystallization, and protect the cell membrane from cold-induced damage. In this article, a review on the current knowledge of the structure and the function of these three types of proteins, which are capable of interacting with ice itself or its nuclei from bacteria.     

中国植物油料蛋白生产现状与发展趋势

对中国主要植物油料蛋白--大豆蛋白、花生蛋白、棉籽蛋白、菜籽蛋白工业的生产现状与发展趋势进行了论述,同时对这4种蛋白的氨基酸组成、营养效价和生物价进行了比较.结果表明,菜籽蛋白的生物价和营养效价最高,其次为大豆蛋白,再次为棉籽蛋白,最后为花生蛋白.目前我国对大豆蛋白开发利用最多,而对于菜籽蛋白和棉籽蛋白,由于脱毒技术等原因,开发利用不足.随着人民生活水平的提高、技术的成熟,这些油料蛋白将得到进一步的开发、利用,市场潜力巨大.     

Formulation,process conditions,and biological evaluation of dairy mixed gels containing fava bean and milk proteins: Effect on protein retention in growing young rats

Food formulation and process conditions can indirectly influence AA digestibility and bioavailability. Here we investigated the effects of formulation and process conditions used in the manufacture of novel blended dairy gels (called “mixed gels” here) containing fava bean (Vicia faba) globular proteins on both protein composition and metabolism when given to young rats. Three mixed dairy gels containing casein micelles and fava bean proteins were produced either by chemical acidification (A) with glucono-δ-lactone (GDL) or by lactic acid fermentation. Fermented gels containing casein and fava bean proteins were produced without (F) or with (FW) whey proteins. The AA composition of mixed gels was evaluated. The electrophoretic patterns of mixed protein gels analyzed by densitometry evidenced heat denaturation and aggregation via disulfide bonds of fava bean 11S legumin that could aggregate upon heating of the mixtures before gelation. Moreover, fermented gels showed no particular protein proteolysis compared with gel obtained by GDL-induced acidification. Kinetics of acidification were also evaluated. The pH decreased rapidly during gelation of GDL-induced acid gel compared with fermented gel. Freeze-dried F, A, and FW mixed gels were then fed to 30 young (1 mo old) male Wistar rats for 21 d (n = 10/diet). Fermented mixed gels significantly increased protein efficiency ratio (+58%) and lean mass (+26%), particularly muscle mass (+9%), and muscle protein content (+15%) compared with GDL-induced acid gel. Furthermore, F and FW formulas led to significantly higher apparent digestibility and true digestibility (+7%) than A formula. Blending fava bean, casein, and whey proteins in the fermented gel FW resulted in 10% higher leucine content and significantly higher protein retention in young rats (+7% and +28%) than the F and A mixed gels, respectively. Based on protein gain in young rats, the fermented fava bean, casein, and whey mixed proteins gel was the most promising candidate for further development of mixed protein gels with enhanced nutritional benefits.     

菜籽蛋白提取及应用研究进展

该文主要综述菜籽蛋白组成及营养价值,菜籽饼粕脱毒及蛋白质提取方法,并介绍菜籽蛋白在食品工业中应用前景。     

Converting nitrogen into protein--beyond 6.25 and Jones' factors

The protein content in foodstuffs is estimated by multiplying the determined nitrogen content by a nitrogen-to-protein conversion factor. Jones' factors for a series of foodstuffs, including 6.25 as the standard, default conversion factor, have now been used for 75 years. This review provides a brief history of these factors and their underlying paradigm, with an insight into what is meant by "protein." We also review other compelling data on specific conversion factors which may have been overlooked. On the one hand, when 6.25 is used irrespective of the foodstuff, "protein" is simply nitrogen expressed using a different unit and says little about protein (s.s.). On the other hand, conversion factors specific to foodstuffs, such as those provided by Jones, are scientifically flawed. However, the nitrogen:protein ratio does vary according to the foodstuff considered. Therefore, from a scientific point of view, it would be reasonable not to apply current specific factors any longer, but they have continued to be used because scientists fear opening the Pandora's box. But because conversion factors are critical to enabling the simple conversion of determined nitrogen values into protein values and thus accurately evaluating the quantity and the quality of protein in foodstuffs, we propose a set of specific conversion factors for different foodstuffs, together with a default conversion factor (5.6). This would be far more accurate and scientifically sound, and preferable when specifically expressing nitrogen as protein. These factors are of particular importance when "protein" basically means "amino acids," this being the principal nutritional viewpoint.     

鸡肉蛋白和大豆蛋白的相互作用和机理研究

目的:研究鸡肉蛋白和大豆蛋白在转谷氨酰胺酶催化下的相互作用以及经酶改性后的蛋白质对其凝胶性和乳化性的影响,为开发新型鸡肉产品奠定理论基础.方法:应用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)、差示热量扫描(DSC)、荧光光谱等方法研究蛋白质-蛋白质相互作用的机理.结果:酶催化鸡肉蛋白和大豆蛋白发生共价交联反应,生成超大蛋白分子,形成具有三维网络的稳定结构,明显改善了MPI/SPI混合蛋白的凝胶性和乳化性,使混合蛋白的凝胶持水性提高约95％,乳化活性提高约13 m2/g.结论:酶催化鸡肉蛋白和大豆蛋白的共价交联,改善了混合蛋白的凝胶性和乳化性,对大豆蛋白在鸡肉制品中的应用以及改善产品品质提供理论依据.     

葡萄根癌病病原菌中效应蛋白Tae4与其免疫蛋白Tai4的鉴定与分析

葡萄根癌病是一种由葡萄根癌病病原菌引起的革兰氏阴性细菌病害。而革兰氏阴性细菌含有非致病相关效应蛋白Tae4,可以杀死其他竞争菌种。有些革兰氏阴性菌本身可表达免疫蛋白Tai4,使自身免受伤害。本研究鉴定了18个Agrobacterium tumefaciens和4个Agrobacterium vitis株系的Tae4和Tai4蛋白,结果显示,A.tumefaciens含有14个Tae4蛋白,A.vitis含有1个Tae4蛋白和1个Tai4蛋白。通过蛋白性质分析、进化树分析、蛋白结构分析和编码基因的选择压力分析表明,A.tumefaciens Tae4蛋白和A.vitis Tae4蛋白相似度不高;A.tumefaciens Tae4蛋白可分为2组;A.tumefaciens和A.vitis的Tae4基因间遭受正向选择。对葡萄根癌病病原菌株系Tae4蛋白和Tai4蛋白的鉴定与分析将为借助Tae4蛋白消灭致病菌,进而防治病害奠定基础。