酶法糖基化修饰对玉米醇溶蛋白促酒精代谢活性的影响

以含有伯胺基团的壳寡糖为酰基受体,通过转谷氨酰胺酶催化的糖基化反应修饰玉米醇溶蛋白,用体外化学法和动物实验研究了糖基化修饰对玉米醇溶蛋白促酒精代谢活性的影响。实验结果表明,糖基化修饰可以改善玉米醇溶蛋白的促酒精代谢活性,且体外模拟胃肠消化不能破坏糖基化玉米醇溶蛋白的促酒精代谢活性。在蛋白质浓度为2 mg/mL时,糖基化玉米醇溶蛋白的乙醇脱氢酶激活率和羟基自由基清除率为11.83%和20.36%,分别比玉米醇溶蛋白高10.27%和10.57%。在糖基化玉米醇溶蛋白的灌胃剂量为2.0 mg/g bw时,小鼠血液中乙醇浓度为34.49mg/100 mL,与酒精模型组相比降低43.10%,且糖基化玉米醇溶蛋白的剂量与小鼠血醇含量的降低呈现明显的量效关系。     

D-氨基半乳糖修饰对玉米醇溶蛋白结构性质及生物活性的影响

以含有伯胺基团的D-氨基半乳糖为酰基受体,通过谷氨酰胺转氨酶(TGase)催化的糖基化反应修饰玉米醇溶蛋白,分析了糖基化修饰对玉米醇溶蛋白结构性质及生物活性的影响。红外光谱的测定结果表明,在TGase的催化下,玉米醇溶蛋白与D-氨基半乳糖发生了共价结合。在D-氨基半乳糖不存在的反应体系,TGase催化的玉米醇溶蛋白分子间的交联反应发生的概率低,对玉米醇溶蛋白结构性质的影响较小。与玉米醇溶蛋白相比,D-氨基半乳糖的共价结合使玉米醇溶蛋白的游离巯基含量降低67. 45μmol/g,变性温度和总变性焓分别增加8. 8℃和31. 97 J/g,即糖基化增加了玉米醇溶蛋白的热稳定性。糖基化修饰使玉米醇溶蛋白的抗氧化活性(包括DPPH自由基、超氧阴离子自由基和羟自由基清除活性和还原力)和乙醇脱氢酶激活率均显著提高,为进一步研究糖基化玉米醇溶蛋白的护肝活性奠定了理论基础。     

玉米醇溶蛋白酶法糖基化修饰及产物性质研究

以转谷氨酰胺酶为催化剂,壳寡糖为酰基受体,通过糖基化反应修饰玉米醇溶蛋白。以修饰产物中氨基葡萄糖的导入量为指标,采用单因素试验优化糖基化反应条件,并对修饰产物的部分功能性质进行研究。结果表明:壳寡糖糖基化修饰玉米醇溶蛋白的最优条件为:反应初始pH 7.7,温度37℃,底物质量分数3%,酰基供体与酰基受体的物质的量比1∶3,加酶量60 U/g蛋白,反应时间8 h。在此条件下,壳寡糖的接入量最大,为101.47 mg氨基葡萄糖/g蛋白。与玉米醇溶蛋白和交联玉米醇溶蛋白相比,糖基化修饰玉米醇溶蛋白的溶解性和体外消化性均明显改善。     

糖基化及限制性酶解对大豆蛋白结构和抗氧化活性的影响

采用转谷氨酰胺酶催化大豆蛋白与壳寡糖发生糖基化反应,制备糖基化大豆蛋白,随后用胰蛋白酶对其进行限制性酶解,制得水解度为1%、5%、10%和15%的酶解物。分析糖基化及限制性酶解对大豆蛋白的二级结构及抗氧化活性的影响。结果表明:糖基化大豆蛋白的分子发生了交联,酶解物的相对分子质量显著变小,而且分布更加广泛;糖基化大豆蛋白的结构变得无序,酶解导致大豆蛋白的无规则卷曲结构增加;两种修饰技术均能够改善大豆蛋白的抗氧化活性(DPPH自由基清除能力、还原力及亚铁离子螯合能力);糖基化及随后的酶解作用显著改变了大豆蛋白的表观黏度和黏弹特性。     

糖基化修饰对乳清蛋白界面性质的影响

本研究利用转谷氨酰胺酶(TGase)的催化特性,以及氨基糖和壳寡糖的伯胺活性,通过酶法的糖基化途径分别将氨基葡萄糖、壳寡糖导入到乳清蛋白分子中,达到改善乳清蛋白界面性质的目的。修饰反应可以提高乳清蛋白的持水性、吸油性和流变学性质,但降低它的乳化性质。氨基葡萄糖和壳寡糖的修饰产物,持水性分别提高24.25%和53.00%,吸油性分别提高1.50倍和2.85倍,分散液的表观黏度显著提高,动态模量增加且弹性模量始终高于黏性模量。但是,两种糖修饰产物的乳化活性分别降低36.00%和45.89%,乳化稳定性则分别降低22.14%和30.78%。由此结论,在转谷氨酰胺酶的催化下,利用氨基葡萄糖、壳寡糖的乳清蛋白糖基化修饰,可以改善它的某些功能性质。     

D-氨基半乳糖酶法糖基化修饰玉米醇溶蛋白的条件优化及产物部分功能性质研究

以转谷氨酰胺酶为催化剂、D-氨基半乳糖为酰基受体,通过糖基化反应修饰玉米醇溶蛋白,以修饰产物中D-氨基半乳糖的导入量为指标,采用单因素实验优化糖基化反应条件,并对修饰产物的部分功能性质进行了研究。结果表明:D-氨基半乳糖糖基化修饰玉米醇溶蛋白的最优条件为初始pH 7.5,反应温度37℃,底物浓度3%,酰基供体与酰基受体的摩尔比1∶3,加酶量60U/g蛋白,反应时间10h。在此条件下,D-氨基半乳糖的接入量最大,为12.55mg/g蛋白。与玉米醇溶蛋白和交联玉米醇溶蛋白相比,糖基化修饰玉米醇溶蛋白的表面疏水性显著下降,表明其溶解性明显改善。     

体外消化对壳寡糖糖基化修饰玉米谷蛋白生物活性的影响

以壳寡糖糖基化修饰玉米谷蛋白为原料,采用胃蛋白酶和胰蛋白酶对其进行一步消化和二步消化,研究体外消化对糖基化修饰玉米谷蛋白的抗氧化活性和体外促酒精代谢等生物活性的影响。试验结果表明:糖基化修饰和体外消化均可以明显改善玉米谷蛋白的抗氧化活性(包括DPPH自由基清除活性和还原力)和体外促酒精代谢活性。经胃蛋白酶-胰蛋白酶二步消化后,糖基化修饰使玉米谷蛋白的体外消化率提高18.08%,提高了玉米谷蛋白的营养品质。     

糖基化改性对鲣鱼加工副产物活性肽抗氧化能力的影响

目的 本研究利用酶法糖基化修饰鲣鱼加工副产物酶解产物,优化反应条件,制备具有强抗氧化活性和高接枝度的修饰产物,并对产物进行抗氧化活性评价。方法 通过胰酶酶解鲣鱼加工副产物,利用转谷氨酰胺酶（Transglutaminase,TGase）和D-氨基葡萄糖（D-glucosaminase,D-GlcN）酶法糖基化修饰酶解物;采用单因素实验和响应面法优化反应条件;使用羟自由基测定试剂盒等对修饰产物的进行四个指标的抗氧活性评价。结果 酶法糖基化修饰的最优条件为:粗蛋白浓度为40 mg/ml,氨基糖与粗蛋白浓度比为1:1,TGase添加量为108 U/g,反应pH=7.5,反应温度50℃,反应时间5 h。此条件下得到的修饰产物具有很强的抗氧化能力:清除1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基的半抑制质量浓度（median inhibitory concentration, IC50）值为10.02 mg/mL,清除羟自由基的IC50值为2.94 mg/mL;当质量浓度为10 mg/mL时,修饰产物的总抗氧化能力值为0.78 TEAC（Trolox Equivalent Anyioxidant Capacity）,铁离子还原能力值为1.97 OD700（700 nm下测定的吸光度）。结论 鲣鱼胰酶酶解物经过TGase和D-GlcN糖基化修饰后,相比修饰前,具有更强的抗氧化活性,具备作为功能食品原料的潜力。     

酶法制备黑莓果胶寡糖及其抗氧化活性研究

对黑莓果胶寡糖进行抗氧化活性研究,探究其自由基清除能力。对黑莓果胶进行提取,并利用果胶酶对其进行酶解,通过分级醇沉制得黑莓果胶寡糖。以DPPH、ABTS、羟自由基清除能力验证不同黑莓果胶寡糖体外抗氧化活性。结果表明,4倍醇沉寡糖对DPPH、ABTS自由基的IC50分别为0.59、4.75 mg/m L。10倍醇沉果胶寡糖对这两种自由基的清除作用更强,IC50分别为0.40、2.79 mg/m L。黑莓果胶寡糖具有显著的抗氧化活性,对DPPH自由基、ABTS自由基有很强的清除作用,且具有明显的量效关系。     

酶法糖基化修饰对玉米醇溶蛋白物化性质的影响

以D-氨基半乳糖为酰基受体,转谷氨酰胺酶为催化剂,对玉米醇溶蛋白进行酶法糖基化改性,分析了D-氨基半乳糖的共价结合对玉米醇溶蛋白物化性质的影响。实验结果表明:与玉米醇溶蛋白相比,糖基化玉米醇溶蛋白的乳化活性/乳化稳定性、起泡性/泡沫稳定性和体外消化能力均增加,而持水性和吸油性下降。在剪切速率为(1~100)s—1条件下,糖基化玉米醇溶蛋白分散液的表观黏度最高,并且表现出剪切稀化特性;在频率为(0.1~10)Hz条件下,交联玉米醇溶蛋白和糖基化玉米醇溶蛋白分散液的弹性模量均大于黏性模量,表现为类固体特征。     

TGase催化玉米醇溶蛋白糖基化改性

利用转谷氨酰胺酶（transglutaminase,TGase）催化玉米醇溶蛋白与氨基葡萄糖盐酸盐（glucosamine hydrochloride,GAH）发生交联反应。通过SDS-聚丙烯酰胺凝胶电泳确认玉米醇溶蛋白与GAH发生交联反应。以玉米醇溶蛋白糖基化修饰产物中GAH导入量为指标,优化糖基化反应条件,并对玉米醇溶蛋白糖基化修饰样品的溶解性进行了表征。结果表明,最适的糖基化反应条件为底物质量浓度5 g/100 mL、TGase添加量50 U/g（以玉米醇溶蛋白计）、玉米醇溶蛋白中酰基供体与GAH中的酰基受体物质的量比1∶6、初始pH 8.0、反应温度44 ℃、反应时间7 h;此反应条件下,玉米醇溶蛋白中GAH的最大导入量为（11.34±0.21） mg/g（以玉米醇溶蛋白计）。与玉米醇溶蛋白相比,玉米醇溶蛋白交联样品与糖基化修饰样品的溶解性均得到提高,玉米醇溶蛋白糖基化修饰样品的溶解性最高。     

Antioxidant activities and functional properties of tea seed protein hydrolysates (Camellia oleifera Abel.) influenced by the degree of enzymatic hydrolysis

Antioxidant activities and functional properties of tea seed protein hydrolysates (TSPH) prepared using alcalase with different (10, 20, 30 and 40%) values of the degree of hydrolysis (DH) were investigated. The effect of hydrolysis time on antioxidant activity was also investigated. As the hydrolysis time was extended, the DPPH radical scavenging activity increased and finally reached a plateau, the copper chelating capacity decreased, and the superoxide radical scavenging and iron chelating activities increased initially, then subsequently slowed. The solubility, foaming properties, and emulsification properties of TSPH were affected by pH and DH. As the DH value increased, the DPPH radical scavenging activity and the reducing power increased and the copper chelating capacity decreased. TSPH at 20 and 30% DH values exhibited higher superoxide radical scavenging and stronger iron chelating activities respectively, than TSPH at other DH values. The DH value of TSPH affected the antioxidant activity and functional properties.     

Characteristics of edible films made from dairy proteins and zein hydrolysate cross-linked with transglutaminase

The main objectives of this research were to develop whey protein or casein films incorporating zein hydrolysate and also cross‐linked by transglutaminase as to well as characterize the physical and mechanical properties of the film. Zein hydrolysate decreased the solubility of the whey protein film (P < 0.05), while treatment with transglutaminase did not change the solubility of the film significantly. Electrophoresis patterns demonstrated that casein molecules were cross‐linked by transglutaminase and the extent of this cross‐linkage was further increased when zein hydrolysate was added. In addition, the use of zein hydrolysate decreased the tensile strength of the whey protein film by 35–45%. The elongation of the casein film was increased by 41% because of the action of transglutaminase and zein hydrolysate (P < 0.05). The water vapour permeability of the films was not significantly different. As the addition of zein hydrolysate and treatment with transglutaminase improved the flexibility of the films, the level of plasticizer required to maintain film flexibility could be reduced without sacrificing their water vapour permeability.     

玉米后熟期间醇溶蛋白结构和理化特性

将新采收的玉米在温度15 ℃及25 ℃、相对湿度55%条件下进行恒温恒湿贮藏,研究玉米后熟期间玉米醇溶蛋白结构特征及理化特性,并分析二者之间的构效关系。结果发现,玉米在15 ℃及25 ℃后熟56 d期间内,玉米醇溶蛋白的游离巯基含量降低,二硫键含量升高,表面疏水性降低,Zeta电位的绝对值增加,粒径和分散指数降低。玉米后熟期间玉米醇溶蛋白中氢键缔合下降,更多有序的β-折叠转化至无序结构,且后熟作用导致玉米醇溶蛋白热稳定性和α-玉米醇溶蛋白亚基的分子质量降低。此外,玉米后熟显著改变了蛋白的理化特性,在15 ℃后熟42 d和25 ℃后熟28 d,玉米醇溶蛋白的溶解性和持水性均达到最大,在2 个温度下后熟14 d时乳化活性和起泡性均显著增加,而后熟作用导致持油性下降。玉米后熟过程中玉米醇溶蛋白理化特性的改善可能与蛋白质聚集程度降低及其柔性结构相关。结果表明,适当的玉米后熟能够修饰玉米醇溶蛋白结构,进而改善其理化特性。     

Evaluation of mechanical and water barrier properties of transglutaminase cross‐linked zein films incorporated with oleic acid

In this study, four concentrations of transglutaminase were used in zein films incorporated with four oleic acid concentrations, and subsequently, the mechanical and water barrier properties were evaluated. Enzyme concentration significantly affected mechanical and barrier properties of the films. Transglutaminase concentration at 1% improved tensile strength of control sample from 17.5 to 26.9 MPa while solubility decreased from 6.4% to 4.4%. Incorporation of oleic acid into transglutaminase‐treated zein films irrespective of enzyme concentration decreased water vapour permeability and solubility with the 1% transglutaminase‐treated zein films incorporated with 3% oleic acid registering the lowest permeability (0.37 g mm m^?2 h^?1 kPa^?1) and solubility (2.8%) values while elongation at break was not significantly improved. The use of transglutaminase at 1% concentration in cross‐linking zein films coupled with incorporation of controlled concentrations of oleic acid can be an effective approach in improving mechanical and water barrier properties of zein‐based films.     

基于壳聚糖的抗氧化复合材料制备及其在食品包装中的应用

本文以壳聚糖为主体材料,在其侧链接枝天然的具有抗氧化作用的芳胺类化合物腺嘌呤来增加它的抗氧化活性,并选用具有更高长径比的纳米纤维素掺杂制备高强度的改性壳聚糖复合膜。通过红外光谱、核磁共振碳谱和元素分析对改性壳聚糖进行结构鉴定,证明了腺嘌呤的接枝成功。抗氧化实验结果表明,腺嘌呤改性后的壳聚糖膜抗氧化活性得到显著提升,DPPH自由基清除率能达到72.20%,而纳米纤维素的掺杂增加了壳聚糖膜的机械性能和尺寸稳定性,MCBC-CNF-2膜的拉伸强度能达到65.06MPa,吸水率和溶胀率分别仅为36.20%和6.06%,尽管随着纳米纤维素掺杂量的增加,改性壳聚糖膜的抗氧化活性有所降低,但MCBC-CNF-2膜的DPPH自由基清除率仍能达到54.20%。这种全生物质膜科生物降解并且成本较低,有望应用于食品包装材料。     

Physicochemical and functional properties of chitosans affected by storage periods of crab leg shell

Effects of storage period (0, 1, 2, 3 and 4 months) of crab leg shell at room temperature on selected physicochemical and functional properties of E‐ and G‐chitosans, respectively, prepared from entire (E) and ground (G) shells were evaluated. Increased storage period of crab shell generally increased degree of deacetylation (DD) and viscosity, but decreased DPPH radical scavenging activity of both chitosans. Water‐binding (WBC) and fat‐binding (FBC) capacities of E‐chitosan were not affected by storage period of crab shell; however, those of G‐chitosan significantly increased when crab shell was stored for more than 1 month. Dye‐binding capacity (DBC) of both chitosans decreased when crab shell was stored for 1 month, but further decrease was not observed with increased storage period to 4 months. Prepared with 4‐month stored crab shell, E‐chitosan exhibited comparable viscosity, colour whiteness index, DPPH radical scavenging activity and DBC, but lower DD, WBC and FBC than G‐chitosan.     

壳聚糖及其衍生物的抗氧化作用

采用邻二氮菲-Fe2+氧化法和DPPH法,研究5种壳聚糖及其衍生物——壳聚糖(chitosan)、壳寡糖(ol-igo-chitosan)、羧甲基壳聚糖(CM-chitosan)、N-乙酰氨基葡萄糖(GLcNAc)、氨基葡萄糖盐酸盐(GlcNH2.HCl)的体外清除羟自由基和DPPH.自由基的能力。结果表明:在实验设置的浓度范围内,对羟自由基的清除能力依次为oligo-chitosan>chitosan>GLcNAc>GlcNH2.HCl>CM-Chitosan,且其清除能力随着浓度的增加而增加。其中2 mg/mL的Oligo-chitosan对羟自由基的清除率最大达到97.81%,相当于4 mmol/L的VC对羟自由基的清除能力。对DPPH.的清除能力大小依次为oligo-chitosan>chitosan>GlcNH2.HCl≥GLcNAc>CM-chitosan,且其清除能力随着浓度的增加而增加。2 mg/mL oligo-chitosan的清除率为97.34%,大于6mmol/L VC的清除速率79.92%。2种方法测定的结果比较一致。     

Effect of ultrafine grinding on hydration and antioxidant properties of wheat bran dietary fiber

Wheat bran dietary fiber (DF) powders was prepared by ultrafine grinding, whose effects were investigated on the composition, hydration and antioxidant properties of the wheat bran DF products. The results showed that ultrafine grinding could effectively pulverize the fiber particles to submicron scale. As particle size decrease, the hydration properties (water holding capacity, water retention capacity and swelling capacity) of wheat bran DF were significantly (p < 0.05) decreased and a redistribution of fiber components from insoluble to soluble fractions was observed. The antioxidant activities of wheat bran and DF before and after grinding were in terms of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, ferrous ion-chelating activity, reducing power and total phenolic content (TPC). Compared with DF before and after grinding, micronized insoluble DF showed increased chelating activity, reducing power and TPC yet decreased DPPH˙ radical scavenging activity. Positive correlations were detected between chelating activity, reducing power and TPC.     

玉米醇溶蛋白肽的超滤膜分级及产物的体外生物活性

为探究分子质量对玉米醇溶蛋白肽体外生物活性的影响,以玉米醇溶蛋白为原料,采用碱性蛋白酶Alcalase酶解制备玉米醇溶蛋白肽,采用截留分子质量为5、3 ku和1 ku的超滤膜对玉米醇溶蛋白肽进行顺次分级分离,获得分子质量大于5 ku、3~5 ku、1~3 ku和小于1 ku 4个组分,通过测定各组分的抗氧化活性和乙醇脱氢酶激活活性,表征超滤膜分级对玉米醇溶蛋白肽体外生物活性的影响。结果表明：用碱性蛋白酶Alcalase酶解玉米醇溶蛋白2 h时,清除DPPH自由基的玉米醇溶蛋白肽组分分子质量分布在1~5 ku范围内;螯合亚铁离子、清除羟自由基和激活乙醇脱氢酶的玉米醇溶蛋白肽组分的分子质量集中在小于1 ku;而玉米醇溶蛋白肽的超氧阴离子自由基清除活性和还原力受其分子质量大小影响较小。综上,分子质量对玉米醇溶蛋白肽的生物活性影响较大,可以选用超滤膜对玉米醇溶蛋白肽活性组分进行分级和富集。