温度条件对乳清蛋白糖基化反应特性和抗氧化活性的影响

利用糖基化修饰技术,以乳清分离蛋白(WPI)为研究对象,以褐变程度、pH值以及抗氧化活性为检测指标,研究反应温度对乳清蛋白糖基化反应特性和抗氧化活性的影响。研究结果表明:反应温度越高,糖基化反应后产物的pH值越低,褐变程度越大,抗氧化活性越强。不同类型糖基复合物的抗氧化活性随反应温度增大有不同程度的提高,其他核糖-WPI体系中抗氧化活性最强,其次分别为半乳糖-WPI>果糖-WPI>葡萄糖-WPI>乳糖-WPI。     

金属离子、半胱氨酸、磷酸盐和乙醇对菊粉糖基化乳清分离蛋白褐变和抗氧化活性的影响（英文）

研究金属离子、半胱氨酸、磷酸盐和乙醇对糖化乳清分离蛋白(whey protein isolate,WPI)-菊粉结合物褐变和抗氧化活性的影响。随着铁、锌离子浓度的增加,糖基化WPI-菊粉结合物的褐变和抗氧化活性先升高后降低,而游离氨基含量先降低后升高。当铜离子质量浓度为0～150 mg/L时,糖基化WPI-菊粉结合物的褐变和抗氧化活性增强,而游离氨基含量下降。半胱氨酸不仅能抑制糖基化反应的褐变,而且能提高WPI-菊粉结合物的抗氧化活性。磷酸缓冲液和乙醇对糖基化反应有促进作用,而磷酸盐缓冲液促进作用较大。因此,金属离子、磷酸盐和乙醇可促进WPI-菊粉的糖基化反应,增强其抗氧化活性。     

乳清分离蛋白美拉德反应产物的体外抗氧化特性

以乳清分离蛋白和木糖、葡萄糖、果糖、蔗糖、麦芽糖、乳糖为美拉德反应原料,研究蛋白与糖的种类及混合比例对褐变程度的影响,并对反应产物进行抗氧化活性检测。结果表明:木糖与乳清分离蛋白按质量比2:1混合,湿热糖基化反应后,褐变程度最强,且在乳清分离蛋白与木糖按质量比2:1条件下反应后,乳清分离蛋白-木糖体系的美拉德反应产物(MRPs)具有较高还原能力和抗脂质过氧化能力及对DPPH自由基和O-2.具有较高的清除能力。     

高压均质对乳清蛋白糖基化产物抗氧化的影响

通过干法糖基化,以一定质量比例乳清蛋白和岩藻多糖(1︰3)作为糖基化反应原料,研究不同均质压力(0, 70和120 MPa)条件下乳清蛋白和岩藻多糖糖基化产物反应特性以及体外抗氧化活性。试验结果表明,高压均质可促进蛋白质和多糖的糖基化反应,乳清蛋白-岩藻多糖混合物在294 nm和420 nm的吸光度随着均质压力的增加而显著变化(p0.05), 120 MPa条件处理下的样品的褐变程度要远大于未处理组。DPPH自由基清除率试验结果表明,乳清蛋白-岩藻多糖混合物经高压均质处理后可提高其抗氧化能力,但是随着糖基化反应进行,乳清蛋白-岩藻多糖糖基化产物DPPH自由基清除率无显著差异(p0.05)。     

pH值对乳清蛋白糖基化产物体外抗氧化特性的影响

选择6种不同的糖基配体,通过湿热糖基化反应,研究乳清蛋白不同糖基化复合物在不同pH值下的反应特性及抗氧化特性。结果表明:在pH值3～9的条件下,6种乳清蛋白糖基化复合物与乳清蛋白420nm和294nm处的吸光值差异显著(P<0.05);且6种乳清蛋白糖基化复合物的游离氧基酸含量均显著降低(P<0.05)。除了乳清蛋白-蔗糖复合物外,其他5种乳清蛋白糖基化复合物的还原能力、DPPH自由基清除能、·OH自由基清除能力和抗脂质过氧化能力随pH值的升高都有所提高。乳清蛋白-木糖复合物的抗氧化能力提高最大,而且在pH值7～9的反应条件下,具有比V_c更高的还原能力。     

温度对金带细鲹鱼肉水解物美拉德反应及其产物抗氧化性的影响

采用金带细鲹鱼肉蛋白为研究对象,以pH值、中间产物、褐变程度、游离氨基酸含量及抗氧化活性为检测指标,研究温度(100,120℃)对金带细鲹鱼肉蛋白水解物美拉德反应及其产物抗氧化活性的影响。结果表明:当反应温度为120℃时,反应体系的pH值、中间产物(A294nm)、褐变程度(A420nm)及游离氨基酸含量,随着美拉德反应时间的延长与100℃相比变化更加显著,反应产物的还原力和DPPH自由基清除率大幅度提高,而羟自由基清除率和Fe2+螯合能力下降明显。     

酪蛋白与还原糖美拉德反应产物抗氧化性的研究

采用酪蛋白同还原糖（葡萄糖∶乳糖=1∶1）发生美拉德反应,研究其美拉德反应产物（MRPs）的抗氧化活性,测定了MRPs的还原力和对DPPH自由基的清除率。根据单因素及正交实验结果表明,酪蛋白与还原糖反应得到的美拉德反应产物的抗氧化活性同反应物浓度、反应温度、反应时间、反应起始pH存在一定的量效关系,并且确定酪蛋白浓度为3%、反应温度为100℃、反应时间为6h、反应起始pH10时是最佳美拉德反应模式,此时MRPs的抗氧化活性较强,DPPH·清除率可达72.87%。     

由碱性蛋白酶制备的乳清蛋白水解物抗氧化活性的研究

通过碱性蛋白酶水解乳清蛋白以研究乳清蛋白水解物的抗氧化活性。通过测定水解物对卵磷脂脂质氧化体系的氧化抑制作用、亚铁还原能力、DPPH自由基清除能力,研究乳清多肽抗氧化活性的大小。结果表明,乳清多肽的抗氧化能力与底物浓度、加酶量、水解时间、pH值、温度等有关,水解的最佳工艺条件是底物质量浓度50g／L,pH值8．5,加酶量（E／S）2％,温度65℃,水解时间为5h。研究表明,碱性蛋白酶制备的乳清蛋白水解物在卵磷脂脂肪氧化体系中可以降低硫代巴比妥酸值（TBARs）,且具有较好的还原能力和清除自由基的能力,因而具有较好的抗氧化活性。     

糖基化改性对英国红芸豆抗氧化肽抗氧化活性的影响

为了提高英国红芸豆抗氧化肽的抗氧化活性,利用木糖对其进行糖基化改性。首先利用单因素和正交试验对糖基化改性条件进行优化,然后利用荧光光谱、紫外-可见光谱和傅里叶中红外光谱对糖基化改性产物进行分析。研究结果表明,糖基化改性的最佳反应条件为：抗氧化肽浓度 10 mg/mL、反应温度 90℃、pH 7、反应时间 4 h、糖肽比为 1:1；在此条件下制备的糖基化产物的羟基自由基清除率、DPPH自由基清除率、还原力和亚铁离子螯合能力分别提高了80.9%、75.1%、135.7%、27.2%,褐变程度为 0.52,接枝度为 39%。糖基化改性产物的荧光和紫外吸收特性增强,产物的 -OH 含量增加,在 N-H、C=O 和 C-N 键都发生了伸缩和振动。糖基化改性可以显著提高英国红芸豆抗氧化肽的抗氧化活性。     

亚麻籽胶-乳清蛋白改性物的制备及抗氧化性

利用亚麻籽胶对乳清蛋白进行糖基化改性，以接枝度为指标进行单因素及正交试验得到最佳反应pH,温度和时间，并对所得亚麻籽胶-乳清蛋白复合物进行扫描电镜、红外光谱、抗氧化性等测定。得到最佳制备条件为：pH 11、110℃、60 min。产物表面结构的变化、傅立叶变换红外光谱以及荧光分析证实了结合物的产生。抗氧化性测定结果显示，无论亚麻籽胶是否脱蛋白，其与乳清蛋白复合物的抗氧化能力均高于同等浓度下单一的亚麻籽胶和乳清蛋白，未脱蛋白亚麻籽胶所得复合物的抗氧化能力优于脱蛋白亚麻籽胶复合物。相关性分析表明，亚麻籽胶添加量与其所得复合物的接枝度、抗氧化能力均呈正相关。研究表明亚麻籽胶与乳清蛋白结合增强了两者的功能性质。     

Properties of whey protein isolate–dextran conjugate prepared using pulsed electric field

Effect of pulsed electric field treatment on whey protein isolate-dextran conjugation in aqueous solution via Maillard reaction was investigated. Significant changes in browning intensity, free amino group content and SDS-PAGE profile showed that whey protein isolate-dextran conjugate was successfully formed using pulsed electric field treatment. Moreover, higher pulsed electric field intensity enhanced the extent of glycosylation. Meanwhile, the secondary structure of whey protein isolate had a considerable loss due to the covalent attachment of dextran. The functional properties, such as solubility, emulsifying activity and emulsion stability were also evaluated. Compared with initial whey protein isolate, the solubility and emulsifying properties were significantly improved. At the same time, glycosylation also inhibited heat-induced aggregation after treated at 80 °C for 20 min. All data showed that pulsed electric field treatment could be applied as a means to prepare WPI-dextran conjugate with better functional properties.     

Physicochemical and antioxidant properties of Maillard reaction products formed by heating whey protein isolate and reducing sugars

This study was conducted to investigate the physicochemical and antioxidant properties of Maillard reaction products (MRP) prepared by heating whey protein isolate (WPI) and reducing sugars (glucose and galactose) to 95 °C for different lengths of time (0–6 h). The results revealed that the colour, intermediate products, browning intensity and the antioxidant activities of the MRP increased as the reaction time increased (P < 0.05), whereas the pH value and free amino group content decreased (P < 0.05). Sodium dodecyl sulphate–polyacrylamide gel electrophoresis indicated that the covalently linked conjugates of WPI and sugars were formed. The results indicate that the Maillard reaction could improve the antioxidant capacity of WPI.     

Effect of reactant concentrations on the Maillard reaction in a fructose–glycine model system and the inhibition of black tiger shrimp polyphenoloxidase

The characteristics and the inhibitory activity towards black tiger shrimp polyphenoloxidase of Maillard reaction products (MRPs), prepared by heating an equimolar mixture of fructose and glycine at various concentrations (0.75–30 mM) at 100 °C for 12 h, were investigated. Increase in the intermediate products was observed with increasing reactant concentration, as evidenced by the increase in A₂₉₄ and fluorescence intensity. Furthermore, development of browning (A₄₂₀) was noticeable when the reactant concentration increased. The inhibitory activity of MRPs towards PPO gradually increased when the concentration of each reactant increased and reached a maximum at 30 mM (80% inhibition). The increase in the inhibitory activity of MRPs was coincidental with the increase in the reducing power, A₂₉₄, fluorescence intensity, as well as browning intensity. Generally, the development of Maillard reaction products was associated with decrease in pH and loss of reducing sugar and free amino groups, with coincidental increase in reducing power and copper-chelating property. MRPs with the reactant concentration of 4.5–30 mM were able to chelate the copper ion. Therefore, the inhibitory activity of MRPs towards browning, induced by PPO, was most likely due to their copper-chelating property as well as reducing power.     

改性乳清蛋白体外抗氧化特性

以木糖、葡萄糖、果糖、乳糖、麦芽糖、蔗糖和乳清蛋白为美拉德反应原料,按照一定比例进行湿热糖基化反应。结果表明:在湿热糖基化反应后,6种糖类与乳清蛋白复合物在420 nm和294 nm处的吸光值差异显著(P<0.05);除乳清蛋白-蔗糖复合物外,其他5种乳清蛋白糖基复合物的游离氨基酸含量均显著降低(P<0.05)。除了乳清蛋白-蔗糖复合物外,其他5种乳清蛋白糖基化复合物随浓度的增加,还原能力和DPPH自由基清除能力都有所提高,其中乳清蛋白-木糖复合物的抗氧化能力提高最大,而且SDS-PAGE显示乳清蛋白-木糖复合物反应后分子质量明显增大;傅里叶红外光谱(FTIR)结果显示,乳清蛋白-木糖和乳清蛋白-葡萄糖复合物中蛋白质的酰胺I和II明显减少。     

Ultrasound assisted vis-à-vis classical heating for the conjugation of whey protein isolate-gellan gum: Process optimization,structural characterization and physico-functional evaluation

In the present work, ultrasonic assisted synthesis and characterization of Maillard conjugates of whey protein isolate (WPI) and gellan gum (GG) was carried out and compared with the classical heating method. Conjugation was confirmed by FTIR, secondary structure, intrinsic fluorescence analysis, and degree of glycation (DG). The structural analysis revealed high protein unfolding by sonication confirming loss of α-helix content and exposing more amino groups to the conjugation reaction. Color change analysis confirmed that ultrasonication accelerated the initial stage of Maillard reaction but did not form the advanced Maillard reaction products. Ultrasonication gave higher DG in lesser time (17.22% in 60 min) than classical heating method (8.41% in 4 h). Physico-functional properties such as pH and thermal stability, emulsifying activity index, emulsion stability index, foaming capability and antioxidant activity of WPI-GG conjugates prepared by ultrasonic treatment were superior to classical heating method suggesting ultrasonication as a potentially alternative method for Maillard conjugation.Industrial relevanceImprovising supplementary protein functionality by conjugation with food grade polysaccharides like gellan gum through ultrasonication could make the process more controllable and economical. The undesired browning can be inhibited in ultrasonic assisted conjugate synthesis and hence the overall acceptance of the final product can be increased.     

美拉德糖基化对玉米蛋白粉双酶水解产物抗氧化活性的影响

利用复合蛋白酶和碱性蛋白酶协同作用于玉米蛋白粉,将得到的双酶水解产物与壳寡糖进行美拉德糖基化反应,研究不同蛋白浓度下的酶解物和糖基化产物的抗氧化活性。结果表明,酶解物和糖基化产物都具有良好抗氧化活性,美拉德糖基化反应可以提高酶解物的抗氧化活性。当糖基化产物蛋白浓度为5.00 mg/mL时,其·OH清除率和DPPH·清除率分别达到了90.91%和61.75%,蛋白浓度为1.00mg/mL时,Fe~(2+)螯合能力为83.42%,比酶解物·OH清除率和DPPH·清除率分别提高了48.78%和32.26%,Fe~(2+)螯合能力提高了22.63%。     

Effect of the Reactant Ratio on the Characteristics and Antioxidant Activities of Maillard Reaction Products in a Porcine Plasma Protein Hydrolysate-Galactose Model System

The chemical characteristics and antioxidant properties of Maillard reaction products formed in the Maillard reaction in a model system at 95°C for different lengths of time (0–6 h) were investigated at three mass ratios (1:1, 1:2, and 1:3) of porcine plasma protein hydrolysate to galactose. The results revealed that the pH value and free amino group content decreased (p < 0.05), whereas the browning index, intermediate products, and browning intensity, as well as reducing power and 2,2’-amino-di(2-ethyl-benzothiazoline sulfonic acid-6)ammonium salt radical scavenging activity of the Maillard reaction products increased as the reaction time increased (p < 0.05). Moreover, when the mass ratio of porcine plasma protein hydrolysate to galactose was 1:3, the Maillard reaction progressed easily, which rendered a higher degree of glycation and antioxidant activity (p < 0.05). These results indicated that the Maillard reaction can improve the antioxidant capacity of porcine plasma protein hydrolysate.     

美拉德反应对乳清分离蛋白及其水解物抗氧化性的影响

以乳清分离蛋白及其蛋白水解物为原料分别与半乳糖发生美拉德反应,研究两者美拉德反应的褐变程度、接枝度及产物荧光光谱的变化,同时以乳清分离蛋白和蛋白水解物作对照,研究两者美拉德反应产物的抗氧化性。结果表明:乳清分离蛋白及其水解物美拉德反应的褐变程度、接枝度及产物的抗氧化性均在4 h达到最大。其中,乳清分离蛋白及其水解物与半乳糖美拉德反应的褐变程度和接枝度最大值分别为1.114、18.431%和1.413、28.273%;两者美拉德反应产物的还原力、2,2’-联氨-二(3-乙基-苯并噻唑-6-磺酸)二铵盐自由基清除能力和1,1-二苯基-2-三硝基苯肼自由基清除能力分别为0.605、46.29%、61.77%和0.923、69.81%、78.43%,均显著高于对照组(P0.05)。同时,内源荧光光谱发现,美拉德反应改变了乳清分离蛋白及其水解物的构象,使二者的结构更加松散。