Improvement of functional properties of peanut protein isolate by conjugation with dextran through Maillard reaction

Reaction mixtures containing peanut protein isolate (PPI) and dextran (1:1 weight ratio) were dry-heated at 60 °C and 79% relative humidity for 7 days. SDS-PAGE analysis indicated that PPI had become complexed with dextran to form conjugates of higher molecular weight. Arachin, accounting for 50% of peanut proteins, was hard to glycosylate with dextran, which might limit the extent of glycosylation of PPI. The thermal stability of PPI was remarkably improved by mixture/conjugation with dextran. Proteins in mixtures/conjugates might have a more compacted tertiary conformation than PPI. The protein solubility of conjugates at pH 4.5-6.0 was remarkably increased compared with the PPI/mixture. Mixture with dextran could significantly improve the emulsifying and foaming properties of PPI (p < 0.05). Conjugation with dextran could further enhance emulsifying and foaming properties of PPI.     

Physicochemical and emulsifying properties of whey protein isolate (WPI)-polydextrose conjugates prepared via Maillard reaction

In this study, whey protein isolate (WPI) and polydextrose (PDX) were used to produce WPI-PDX covalent conjugates via dry-heating Maillard reaction, and their characteristics and functional properties including abilities to emulsify and stabilise the corn germ oil/water emulsions were measured. Compared with WPI alone, the WPI-PDX conjugates had higher water solubility and DPPH radical scavenging ability, and the derived emulsions exhibited good storage stability over 60 days prepared under these conditions: reaction time 24 h, conjugate concentration 4–6%, oil fraction ratio 0.6 and emulsion system pH 3–8. Further, we found that the emulsion possessed the best storage stability under the condition of 4% WPI-PDX conjugates and 0.6% oil fraction. These results provide a potent to prepare a beneficial Maillard conjugation following an optimised reaction condition and highlight the potential use of WPI-PDX conjugates as the emulsifier in food industry.     

大豆分离蛋白及其美拉德反应产物成膜条件探究

本论文研究不同p H（10、11、12）、不同加热温度（70、80、90℃）和不同甘油浓度（0³.0 m L/100 m L）对浓度为6 g/100 m L大豆分离蛋白溶液及大豆分离蛋白-葡萄糖（w/w=1）美拉德反应溶液、大豆分离蛋白-木糖（w/w=1）美拉德反应溶液成膜条件的影响。通过测定大豆分离蛋白-葡萄糖/木糖溶液的色差值及吸光值来判断美拉德反应程度,通过肉眼和手感观察和评价膜的可揭性、颜色和表观特征。实验结果表明:当大豆分离蛋白和糖浓度均为6 g/100 m L的条件下,大豆分离蛋白的成膜条件为甘油浓度:2.5 m L/100 m L、溶液p H11、80℃加热60 min;大豆分离蛋白与木糖美拉德反应产物成膜条件为甘油浓度:0.125 m L/100 m L、溶液p H11、80℃加热60 min;而大豆分离蛋白与葡萄糖在此条件下美拉德反应程度不明显,因此未对其进行膜的制备。      

热烘改性对大豆分离蛋白功能性的影响

研究了利用热处理对大豆分离蛋白(SPI)进行改性。热烘改性对SPI的吸水性、吸油性、发泡性和泡沫稳定性无显著性影响,常温粘度、高温粘度、耐热性、凝胶性和保水性分别比对照提高了118%、135%、108%、81%和83%。比较适宜的热烘改性条件为10min/85℃。     

Improvement of functional properties of acid-precipitated soy protein by the attachment of dextran through Maillard reaction

The functional acid-precipitated soy protein (SAPP)–dextran conjugate was prepared by dry-heated storage at 60 °C under 79% relative humidity (RH) for 5 days through Maillard reaction between the ε-amino of lysine in soy proteins and the reducing-end carbonyl residue in the dextran. The covalent attachment of dextran to SAPP was confirmed by SDS-polyacrylamide gel electrophoresis and gel filtration chromatography. Functional properties of soy protein depend on the structural and aggregation characteristics of their major components (storage globulins 7S and 11S). The conjugate seemed to be predominantly formed by 7S, and the acidic subunits of 11S in soy protein. The emulsifying properties of the SAPP–dextran conjugate were about four times higher than those of SAPP. The solubility of the protein was not enhanced as a result of preheating, but rather it was not decreased when the conjugated protein was heated at 90 °C for 20 min due to the presence of the polysaccharide. The excellent emulsifying properties of SAPP–dextran conjugate were maintained even at pH 3.0 and were further improved at pH 10.0. The object of Maillard reaction is to guarantee the suitable reaction degree, and the resulting soluble conjugate can have excellent emulsifying properties.     

蛋清蛋白、大豆分离蛋白及其美拉德反应产物膜包裹对核桃仁脂质过氧化作用的比较研究

本文通过测定核桃油酸价、过氧化值、丙二醛含量、碘值和DPPH自由基清除率五个指标的变化研究比较蛋清蛋白膜、大豆分离蛋白膜及其与木糖美拉德反应产物膜包裹对核桃仁脂质过氧化的影响。结果表明,随着反应时间（0⁸d）的增加,核桃仁酸价、过氧化值和丙二醛含量均呈现上升趋势,DPPH自由基清除率均呈现下降趋势,而碘值则变化不明显。加热第8d时,四种膜包裹核桃仁的酸价、过氧化值和丙二醛含量均小于未包膜的核桃仁,DPPH自由基清除率高于未包膜的核桃仁。四种膜包裹核桃仁的酸价无显著性差异（p>0.05）;而过氧化值中以蛋清蛋白膜组较高,且其余三组的无显著性差异（p>0.05）;四种膜包裹核桃仁的丙二醛含量均明显低于未包膜组,延缓丙二醛含量上升的效果依次为:大豆分离蛋白-木糖膜>蛋清蛋白-木糖膜>大豆分离蛋白膜>蛋清蛋白膜;大豆分离蛋白-木糖膜包裹核桃仁保留的DPPH自由基清除率明显高于其它三种膜。综上所述,两种蛋白及其美拉德反应产物膜包裹均可延缓核桃仁脂质过氧化,综合各项指标其效果依次为:大豆分离蛋白-木糖膜>蛋清蛋白-木糖膜>大豆分离蛋白膜>蛋清蛋白膜。      

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.     

大豆分离蛋白与麦芽糊精的Maillard反应性及产物乳化性质研究

以SDS-聚丙烯酰胺凝胶电泳和毛细管电泳研究了大豆分离蛋白-麦芽糊精的Maillard反应形成的共聚物。电泳分析表明:7S亚基与麦芽糊精的反应性较高,而且在文中所研究的蛋白质与多糖质量比的范围内,7S亚基都能与麦芽糊精发生定量的共聚合反应,形成分子特性高度一致的共聚物;而11S亚基与麦芽糊精间的反应性较低,共聚物的分子特性受蛋白质与多糖质量比的影响。共聚物在pH7.0和pH4.5时的乳化性能优于酪朊酸钠,尤其是在pH4.5时具有优良的乳化稳定性。但在较高NaCl浓度时的乳化活性与大豆分离蛋白相比没有明显的改善,其乳化稳定性则明显优于酪朊酸钠。     

大豆分离蛋白溶解性和乳化性影响因素研究

研究了pH、大豆分离蛋白(SPI)质量浓度、NaCl浓度、搅拌时间和温度等因素对SPI溶解性和乳化性的影响.结果表明,0.8%的SPI在pH 6.0的条件下,实验浓度范围内的NaCI均使SPI溶解性和乳化性降低,适当的延长搅拌时间和升高温度可以显著提高SPI溶解性和乳化性.在室温条件下,搅拌50 min时SPI溶解度最...     

大豆分离蛋白美拉德反应研究进展

本文首先综述了美拉德反应对大豆分离蛋白的溶解性、乳化性以及凝胶性等一系列功能特性的影响,进而阐述了美拉德反应对大豆分离蛋白生物活性的影响,如抗氧化性和抗菌性。最后对大豆分离蛋白的美拉德反应在食品领域的研究进行了展望,以期对大豆分离蛋白的美拉德反应在食品领域的研究提供参考。     

Formation of soy protein isolate–dextran conjugates by moderate Maillard reaction in macromolecular crowding conditions

BACKGROUND: Several methods have been reported for the conjugation of proteins with polysaccharides. Protein–polysaccharide conjugates can be formed by traditional dry heating, but this process is not attractive from an industrial viewpoint, and no commercial conjugates have been manufactured in this way. In the present study, in order to develop a more practical reaction method, macromolecular crowding was used to attach polysaccharides to proteins. RESULTS: Soy protein isolate–dextran conjugates (SDCs) were prepared via the initial stage of the Maillard reaction in macromolecular crowding conditions. The impact of various processing conditions on the formation of SDCs was investigated. The optimal conditions chosen from the experiments were a soy protein isolate/dextran ratio of 1:1 (w/w), a pH of 6.5, a reaction temperature of 60 °C and a reaction time of 30 h. Circular dichroism spectroscopy showed that the secondary and tertiary structures of the conjugates were changed significantly. Structural flexibility increased, allowing better display of their functional characteristics. The conjugates had a composition with various sizes, especially macromolecules, according to gel permeation chromatography. Thermal analysis showed that the thermal stability of the conjugates was improved. CONCLUSION: The production of SDCs under macromolecular crowding conditions appears to be an effective and promising technique, representing an advance over classic protein glycosylation methods. Copyright © 2012 Society of Chemical Industry     

高压复合pH偏移预处理对大豆蛋白糖基化复合物结构及乳化性质影响

本研究运用超高压处理、碱性pH偏移处理对大豆分离蛋白（soy protein isolate, SPI）进行单独和复合处理后,将其与麦芽糊精进行糖基化反应,并测定不同预处理条件对复合物结构及乳化性质影响。结果表明,与单一超高压处理或pH偏移处理相比,高压协同碱性pH偏移处理对糖基化反应的促进效果更明显。复合处理使糖基化复合物的接枝度与褐变程度增大,二级结构由有序向无序的转变程度增大,蛋白质内部疏水基团暴露量增多,蛋白分子三级结构趋于松散。其中400 MPa高压处理协同碱性pH偏移处理对糖基化改性的促进效果最为显著,所得糖基化样品的乳化活性（31.38 m2/g）和乳化稳定性值（36.88 min）最大,分别为对照组的1.89倍和1.60倍。     

转谷氨酰胺酶交联木瓜蛋白酶水解产物改善大豆分离蛋白乳化特性的研究

为获得适宜添加到冰淇淋等冷冻食品中的大豆分离蛋白（SPI）,利用转谷氨酰胺酶交联木瓜蛋白酶酶解大豆分离蛋白产物来改善大豆蛋白的乳化特性。将样品经高压均质制成O/W型乳状液,研究不同水解程度的水解产物交联后对样品乳状液的粒度分布、表面积平均粒径、离心乳析率等的影响,同时研究了常温放置、低温放置（4℃）以及冷冻-解冻处理对酶改性蛋白乳状液聚集、聚结稳定性的影响。结果表明,SPI和中低度水解（DH2%¹0%）样品经转谷氨酰胺酶交联后乳化活性和乳化稳定性均显著提高,水解度10%样品交联后的乳化活性和乳化稳定性改善最显著。酶改性可以显著改善SPI新鲜乳状液的聚集稳定性,中度水解度（DH6%¹0%）SPI样品交联后聚集程度最低。冷藏不会明显损坏样品的聚集和聚结稳定性。冷冻-解冻处理使乳状液发生聚结现象,SPI乳状液的聚结程度最大,中度水解度（DH6%¹0%）样品交联后的聚结程度最小。因此,可将中度水解SPI交联样品用于对乳化特性要求较高的冰淇淋等冷冻食品中。      

玉米胚芽分离蛋白溶解性和乳化性质的研究

以湿法脱胚的玉米胚芽为原料,采用碱溶酸沉法制备了玉米胚芽分离蛋白。探讨了不同实验条件如温度、pH、盐浓度等对玉米胚芽分离蛋白的溶解性和乳化性的影响,并解释了乳化性和溶解性在实验条件下的变化规律。研究结果表明,玉米胚芽分离蛋白在碱性条件下溶解度较好,55℃时溶解度最大;在pH 7.0~8.5范围内乳化活性明显增加,提高温度可以增加蛋白质的乳化活性。     

大豆分离蛋白起泡性和乳化性影响因素的研究

大豆分离蛋白的乳化性和起泡性与蛋白质、NaCl、卡拉胶、蔗糖和山梨酸钾含量、pH值、加热温度等密切相关。蛋白质质量浓度分别为2.0g/100mL和2.5g/100mL时,大豆分离蛋白乳化性和起泡性分别达到最大值;远离pH4.5,大豆分离蛋白起泡性和乳化性增加;加热温度45℃时起泡性最好,而乳化性最差;氯化钠、卡拉胶、山梨酸钾添加量分别为1.00g/100mL、0.20g/100mL、0.08g/100mL时,起泡性和乳化性好;添加蔗糖会使蛋白质的起泡性下降,而蔗糖添加量6.0g/100mL时乳化性好。     

超高压对大豆分离蛋白乳化性影响

研究超高压对大豆分离蛋白乳化性影响,对不同压力、加压时间、pH对其乳化性影响进行分析,并通过正交试验,最终得出提高大豆分离蛋白乳化性最佳工艺条件,即:作用压力400MPa,处理时间12.5min,pH为8.0;在此条件下,乳化能力与乳化稳定性可分别提高86.6%和24.7%。     

Improvement of functional properties of whey protein isolate through glycation and phosphorylation by dry heating

Whey protein isolate (WPI) was glycated with maltopentaose (MP) through the Maillard reaction, and the MP-conjugated WPI (MP-WPI) was then phosphorylated by dry heating in the presence of pyrophosphate. Glycation occurred efficiently, and the sugar content of WPI increased approximately 19.9% through the Maillard reaction. The phosphorylation of MP-WPI was enhanced with an increase in the dry-heating time from 1 to 5 d, and the phosphorus content of WPI increased approximately 1.05% by dry heating at pH 4.0 and 85°C for 5 d in the presence of pyrophosphate. The electrophoretic mobility of WPI increased with an increase in the phosphorylation level. The stability of WPI against heat-induced insolubility at pH 7.0 was improved by conjugation with MP alone, and further improved by phosphorylation. Although the emulsifying activity of WPI was barely affected by glycation and phosphorylation, the emulsifying stability of phosphorylated MP-WPI (5 d), was 2.2 times higher than that of MP-WPI. Gelling properties such as hardness, resiliency, and water-holding capacity of heat-induced WPI gel were markedly improved, and the gel was rendered transparent by phosphorylation. The calcium phosphate-solubilizing ability of WPI was enhanced by phosphorylation. These results suggested that phosphorylation by dry heating in the presence of pyrophosphate after conjugation with MP is a useful method for improving the functional properties of WPI.     

酱油渣中蛋白的乳化特性研究

对比分析了酱油渣中蛋白(SRP)、糖基化大豆分离蛋白(GSP)和大豆分离蛋白(SPI)的ξ-电位、疏水性以及乳化活性和乳化稳定性。发现SRP的总糖和蛋白含量比为1∶1.4,其中含有大量的糖蛋白;SRP疏水性是SPI的2.5倍。SRP等电点接近pH=3.5,在酸性环境下溶解性较好。在酸性、高盐环境下SRP乳化能力高于GSP和SPI,在pH=5时,SRP的乳化活性(EAI)是SPI的8.1倍,在NaCl浓度为0.3mol/L时,SRP的EAI是SPI的1.77倍。     

大豆分离蛋白的特性研究

研究水解后不同分子量范围的大豆分离蛋白功能性方面,分子量在1000～2000D时候乳化活性和乳化稳定性最大,分别为176.9mL/g和120min;持水性方面分子量小于1000D时候最大,为66.2%;黏度方面,分子量大于4000D时候最大,为1.8cp;持油率方面分子量范围在大于4000D范围内最大,为378.42%。     

Physicochemical and emulsifying properties of mung bean protein isolate as influenced by succinylation

The application of mung bean protein in foods is limited due to its poor functionality. Acylation with succinic anhydride could be used to improve the functionalities of protein. In this study, the influence of the weight ratio of succinic anhydride to protein (0–0.10) on the degree of N-acylation, physicochemical properties and protein functionalities including emulsifying properties of mung bean protein isolates (MPI) were investigated. The extent of N-acylation of MPI increased as the succinic anhydride:protein ratio increased, while the ζ-potential at neutral pH decreased. In addition, succinylation had an impact on the average particle size of MPI depending on the succinic anhydride:protein ratio. Succinylation had no impact on the total and exposed free sulfhydryl groups. Moreover, the isoelectric point (pI) of the succinylated proteins shifted from pH 5 to lower pH. Succinylation increased the emulsifying activity index (EAI), while the impact on the emulsion stability index depended on the succinic anhydride:protein ratio. Thus, succinylation at low succinic anhydride:protein ratio can alter mung bean protein charge and affect physicochemical and functional properties especially emulsifying properties that could be used to increase its utilization.