鲤鱼鱼肉蛋白酶水解物抗氧化性及功能特性

采用碱性蛋白酶对鲤鱼鱼肉蛋白进行酶解,制备不同水解度的水解物。测定水解物的抗氧化活性以及不同pH值条件下水解物的功能特性。结果表明:随着水解度的逐渐升高,水解物的抑制脂质氧化能力、D PP H自由基清除能力、还原能力以及金属离子(Cu2+和Fe2+)螯合能力逐渐增加(P<0.05);同时,水解物的溶解性、乳化性和起泡性都在pH值为4.0(等电点)时达到最低,而后溶解性和乳化性随着pH值升高而增大(P<0.05),而起泡性随着pH值的升高先上升后又下降。因此,鲤鱼鱼肉蛋白碱性蛋白酶水解物可以提高蛋白质的抗氧化活性和溶解性,但是较高的水解度会在一定程度上降低其乳化性和起泡性。     

高速剪切均质对鸡肉肌原纤维蛋白乳化特性和结构的影响

将鸡肉肌原纤维蛋白（myofibrillar protein,MP）-山茶油混悬液进行高速剪切均质（high-speed shear homogenization,HSSH）处理,制得9 种不同剪切速率（11 500、14 500、20 500 r/min）和剪切时间（3、5、7 min）的乳状液样品。研究HSSH对乳液中MP的乳化活性指数（emulsifying activity index,EAI）、乳化稳定性指数（emulsifying stability index,ESI）、溶解度、二级和三级结构的影响,同时研究HSSH对乳液液滴粒径的影响。结果表明：MP的EAI随剪切速率（11 500～20 500 r/min）增加和剪切时间（3～7 min）延长而增大,ESI在剪切速率为14 500 r/min时几乎不受剪切时间影响且均获得＞90%的高值;剪切速率14 500 r/min乳液中MP溶解度最高,11 500 r/min与14 500 r/min组乳状液中MP的二级结构含量随时间延长变化趋势一致,即α-螺旋、β-转角含量随着时间延长逐渐下降,β-折叠和无规卷曲含量则显著升高（P＜0.05）;表征MP三级结构的表面疏水性和活性巯基含量均在20 500 r/min、7 min剪切条件下出现最大值,此时MP的溶解度最小、乳液液滴粒径最大、乳液稳定性最差。因此,适当的HSSH能改变MP的二级和三级结构,并改善MP的乳化活性和乳化稳定性;但过度剪切却导致MP分子过度展开,并造成乳状液失稳。     

Peanut protein concentrate: Production and functional properties as affected by processing

Peanut protein concentrate (PPC) was isolated from fermented and unfermented defatted peanut flour by isoelectric precipitation and physical separation procedures. PPC was dried by spray or vacuum drying. PPC powders from each drying technique were evaluated for proximate composition and functional properties (protein solubility, water/oil binding capacity, emulsifying capacity, foaming capacity and viscosity) along with defatted peanut flour and soy protein isolate as references. PPC contained over 85% protein versus 50% protein in the defatted peanut flour used as raw material for PPC production. PPC had a solubility profile similar to that of peanut flour, with minimum solubility observed at pH 3.5–4.5 and maximum solubility at pH 10 and higher. Roasting of peanut reduced all functional properties of defatted peanut flour while fermentation had the reverse effect. The type of drying significantly affected the functional properties of PPC. Spray dried PPCs exhibited better functional properties, particularly emulsifying capacity and foaming capacity, than vacuum oven dried PPC. Spray dried PPCs also showed comparable oil binding and foaming capacity to commercially available soy protein isolate (SPC). At equivalent concentrations and room temperature, PPC suspension exhibited lower viscosity than soy protein isolate (SPI) suspensions. However, upon heating to 90 °C for 30 min, the viscosity of PPC suspension increased sharply. Results obtained from this study suggest that the PPC could be used in food formulations requiring high emulsifying capacity, but would not be suitable for applications requiring high water retention and foaming capacity. PPC could be a good source of protein fortification for a variety of food products for protein deficient consumers in developing countries as well as a functional ingredient for the peanut industry. The production of PPC could also add value to defatted peanut flour, a low value by-product of peanut oil production.     

酶解产物浓度和油相体积分数对甘薯蛋白酶解产物乳化特性的影响

本文研究了酶解产物浓度(0.10%、0.25%、0.50%、0.75%和1.00%,m/V)和油相体积分数(5%、15%、25%、35%和45%,V/V)对超高压下酶解制得甘薯蛋白酶解产物乳化液显微结构、乳化颗粒平均粒径(d4,3)、乳化活性指数(EAI)、乳化稳定性指数(ESI)和流变学性质的影响。当酶解产物浓度较低和油相体积分数较高时,乳化液的乳化颗粒均一细小。增加甘薯蛋白酶解产物浓度会使其乳化液的d4,3、EAI和ESI均逐渐降低;相反,增加油相体积分数会使乳化液的d4,3逐渐减小,EAI逐渐增大,而ESI则先降低后增加(p0.05)。在酶解产物浓度低和油相体积分数高时,乳化液的初始表观粘度较大,且在1~100 s-1的剪切速率范围内均表现出了剪切变稀现象。酶解产物浓度和油相体积分数与乳化液的d4,3、EAI、ESI和流变学性质密切相关,是影响甘薯蛋白酶解产物乳化特性的重要因素。     

Emulsifying properties of canola and flaxseed protein isolates produced by isoelectric precipitation and salt extraction

The emulsifying (emulsion capacity, EC; emulsion activity/stability indices, EAI–ESI and creaming stability, CS) and physicochemical properties (surface charge/hydrophobicity, protein solubility, interfacial tension, and droplet size) of chickpea (ChPI), faba bean (FbPI), lentil (LPI), and pea (PPI) protein isolates produced by isoelectric precipitation and salt extraction were investigated relative to each other and a soy protein isolate (SPI). Both the legume source and method of isolate production showed significant effects on the emulsifying and physicochemical properties of the proteins tested. All legume proteins carried a net negative charge at neutral pH, and had surface hydrophobicity values ranging between 53.0 and 84.8 (H₀-ANS), with PPI showing the highest value. Isoelectric precipitation resulted in isolates with higher surface charge and solubility compared to those produced via salt extraction. The EC values ranged between 476 and 542 g oil/g protein with LPI showing the highest capacity. Isoelectric-precipitated ChPI and LPI had relatively high surface charges (~−22.3 mV) and formed emulsions with smaller droplet sizes (~ 1.6 μm), they also displayed high EAI (~ 46.2 m²/g), ESI (~ 84.9 min) and CS (98.6%) results, which were comparable to the SPI.     

生物解离大豆乳状液中蛋白质结构特征分析

以不同酶解时间（1、2、3 h）、不同酶添加量（1%、2%）生物解离大豆过程中形成的乳状液蛋白质为研究对象,采用扫描电子显微镜、乳化活性指数（emulsion activity index,EAI）和乳化稳定性指数（emulsion stability index,ESI）、表面疏水性、氨基酸分析及傅里叶变换红外光谱等表征乳状液蛋白质/多肽表面性质及结构特征。结果显示：随着酶解的进行,乳状液中蛋白质由致密有序的网状结构变为疏松、多孔结构,EAI和ESI呈逐渐降低趋势;同时,疏水性氨基酸比例增多,表面疏水性指数（S0）下降,由于疏水性残基之间通过疏水相互作用发生聚集,对蛋白质的疏水区域产生屏蔽作用,导致S0下降;傅里叶变换红外光谱结果显示,随着酶解程度的增加,α-螺旋、β-折叠结构减少,无规则卷曲结构增加,表明酶解过程中引起了分子间作用力变化,导致乳状液蛋白质的构象变化。上述结果是酶解过程中乳状液失稳的主要原因之一,为生物解离乳状液破乳机制提供理论支持。     

Emulsifying properties of sweet potato protein: Effect of protein concentration and oil volume fraction

The effect of protein concentrations (0.1, 0.25, 0.5, 1.0, 1.5 and 2.0% w/v) and oil volume fractions (5, 15, 25, 35 and 45% v/v) on properties of stabilized emulsions of sweet potato proteins (SPPs) were investigated by use of the emulsifying activity index (EAI), emulsifying stability index (ESI), droplet size, rheological properties, interfacial properties and optical microscopy measurements at neutral pH. The protein concentration or oil volume fraction significantly affected droplet size, interfacial protein concentration, emulsion apparent viscosity, EAI and ESI. Increasing of protein concentration greatly decreased droplet size, EAI and apparent viscosity of SPP emulsions; however, there was a pronounced increase in ESI and interfacial protein concentration (P < 0.05). In contrast, increasing of oil volume fraction greatly increased droplet size, EAI and emulsion apparent viscosity of SPP emulsions, but decreased ESI and interfacial protein concentration significantly (P < 0.05). The rheological curve suggested that SPP emulsions were shear-thinning non-Newtonian fluids. Optical microscopy clearly demonstrated that droplet aggregates were formed at a lower protein concentration of <0.5% (w/v) due to low interfacial protein concentration, while at higher oil volume fractions of >25% (v/v) there was obvious coalescence. In addition, the main components of adsorbed SPP at the oil–water interface were Sporamin A, Sporamin B and some high-molecular-weight aggregates formed by disulfide linkage.     

加工工艺对荞麦蛋白功能特性的影响

探讨了加工工艺对荞麦蛋白(BWP)功能特性的影响。pH＜5．0和 pH＞6．0时,喷雾干燥制备的荞麦蛋白(SBWP)的溶解度高于商品大豆分离蛋白(SPI)(P＜0．05)。pH＜7．0时,超声协助提取荞麦蛋白(U- BWP)的溶解度较搅拌提取荞麦蛋白(M-BWP)和脱脂、超声协助提取荞麦蛋白(DU-BWP)好；pH＞7．0时,结果相反。总体来说,BWP 持油能力较 SPI 强,且冷冻干燥制备的荞麦蛋白(F-BWP)的持水、持油能力强于 S-BWP (P＜0．05)。BWP 的乳化活性与其溶解度呈正相关。pH 4．0～5．0时,BWP 的乳化活性指数(EAI)最小而乳化稳定性(ES)最高。脱脂处理明显提高了 BWP 的 EAI 和 ES。     

Food Protein Functionality in a Liquid System: A Comparison of Deamidated Wheat Protein with Dairy and Soy Proteins

ABSTRACT: Solubility, surface properties, overrun, foam stability, apparent viscosity, and emulsification properties were evaluated for 3% protein dispersions of deamidated wheat protein (DWP), sodium caseinate (SC), soy protein isolate (SPI), and whey protein isolate (WPI). DWP dispersion had the highest apparent viscosity, 25% higher emulsion activity index (EAI), and 82% higher emulsion stability index (ESI) when compared to SPI dispersions. Dispersions of DWP had similar foaming properties and surface properties when compared to SC, but had 50% higher EAI and 1000% greater ESI when compared to the 2 dairy proteins. The utilization of DWP could be expanded into liquid food systems currently using dairy proteins.     

离子强度对煮制前后猪肉胶原蛋白乳化特性的影响

为研究离子强度对煮制前后猪肉胶原蛋白乳化特性的影响,测定煮制前后不同NaCl浓度（0.0、0.2、0.4、0.6 mol/L）猪肉可溶性胶原蛋白和不溶性胶原蛋白的乳化特性,包括乳化活性指数（emulsification activity index,EAI）、乳化稳定性指数（emulsion stability index,ESI）、黏度及乳化液微观结构,同时测定猪肉胶原蛋白溶解度。结果表明：随着介质离子强度的提高,猪肉可溶性胶原蛋白溶解度降低,黏度增大,EAI先升高后降低,ESI先降低后升高;猪肉不溶性胶原蛋白溶解度升高,黏度增大,EAI、ESI均呈先升高后降低趋势。改变胶原蛋白的离子强度或对胶原蛋白进行热处理,均能使猪肉可溶性胶原蛋白和不溶性胶原蛋白的乳化特性发生显著变化。     

高压均质对大豆β-伴球蛋白富集组分乳化特性的影响

研究了高压均质对大豆β-伴球蛋白(7S)富集组分乳化活性、乳化稳定性、粒度分布和乳析稳定性的影响。结果表明:与未均质相比,均质处理使7S富集组分乳化活性降低,但可提高其乳化稳定性;乳化活性随均质压力的升高而降低,均质次数对其影响不明显,随着均质压力的升高和均质次数的增多7S富集组分乳化稳定性逐渐提高;高压均质改性的7S富集组分制备的乳状液粒径更小,并且乳析率下降;均质压力不变时,一次均质的7S富集组分比2次均质的7S富集组分形成的乳状液粒径更大,但乳析率降低。     

Effects of Dielectric Barrier Discharge (DBD) Cold Plasma Treatment on Physicochemical and Functional Properties of Peanut Protein

Peanut protein isolate (PPI) solutions were modified by dielectric barrier discharge (DBD) cold plasma (CP) treatment. Effects of CP treatment on the solubility, emulsion stability, and water holding capacity (WHC) of peanut protein were studied. The results showed a significant improvement in solubility, emulsion stability, and WHC following CP treatment. CP treatment resulted in the unfolding of PPI structure, thereby increasing the β-sheet and random coil content and decreasing the α-helix and β-turn content, as analyzed by Fourier-transform infrared spectroscopy. Low-field nuclear magnetic resonance showed an increase in the peak area of T ₂₁ relaxation time by CP treatment and the change in T ₂₁ peak area was in agreement with the result of WHC. This study demonstrated that CP may be successfully applied as a method to modify the functionality of PPI.     

羟自由基氧化对鲤鱼肌原纤维蛋白乳化性及凝胶性的影响

研究羟自由基( ·OH)氧化对鲤鱼肌原纤维蛋白乳化性、凝胶质地及凝胶微观结构的影响。采用由FeCl3、抗坏血酸浓度和不同浓度(0～20mmol/L)H2O2组成的 ·OH氧化体系,对鲤鱼肌原纤维蛋白分别氧化1、3、5h后测定蛋白的乳化活力及乳化稳定性,利用质构仪、扫描电镜对凝胶特性和微观结构进行研究。结果表明：蛋白质氧化会引起鲤鱼肌原纤维蛋白乳化性及凝胶性发生改变,表现在乳化活力和乳化稳定性下降,凝胶弹性、硬度、保水性及白度有不同程度的下降,凝胶微观结构遭到破坏。这些蛋白氧化引起的变化说明,蛋白质氧化对鲤鱼肌原纤维蛋白乳化性及凝胶性能有较大的破坏作用。     

不同干燥方法对花生蛋白功能特性的影响

以花生蛋白为原料,分别采用热风干燥、真空干燥、微波干燥和微波结合真空干燥对花生蛋白进行干燥处理,比较不同的干燥方式对花生蛋白功能特性(吸油性、持水性、乳化性、乳化稳定性、起泡性能和起泡稳定性)的影响。实验表明,微波结合真空干燥的花生蛋白不仅干燥时间短,而且具有较好的功能特性,微波结合真空干燥是一种干燥花生蛋白的适宜方法。     

苏尼特羊宰后成熟过程中肌原纤维蛋白特性与肉品质的变化分析

以6 月龄苏尼特羊股二头肌为材料,测定其宰后成熟过程中（0～3 d）的肉品质、肌原纤维蛋白功能特性和蛋白降解相关指标,旨在探究肌原纤维蛋白对宰后肉品质的影响,并确定苏尼特羊合适的宰后成熟时间。结果表明,4 项肉品质指标（pH值、色泽、剪切力和蒸煮损失率）中,pH值、蒸煮损失率和剪切力在成熟2 d时达到最优值,并与成熟3 d时无明显差异;肌原纤维蛋白的3 种功能特性,即水合特性（溶解度、疏水性）、凝胶特性（凝胶保水性、凝胶硬度）和乳化特性（乳化活性指数（emulsifying activity index,EAI）、乳化稳定性指数（emulsifying stability index,ESI））在成熟1 d时较差,在成熟2 d时有所回升,随后趋于稳定;肌原纤维蛋白降解相关指标,即肌原纤维小片化指数（myofibril fragmentation index,MFI）和十二烷基硫酸钠-聚丙烯酰胺凝胶电泳结果均表明在成熟2 d后蛋白降解程度较小,趋于稳定;相关性分析中,MFI、溶解度、疏水性、EAI、ESI和凝胶保水性与各项肉品质指标间都呈现一定的相关关系。综上所述,苏尼特羊宰后成熟过程中,肌原纤维蛋白的降解与功能特性变化对肉品质有较大影响,并且各主要指标指示在宰后2 d时已基本成熟。     

Effect of pH and NaCl/CaCl2 on the solubility and emulsifying properties of sweet potato protein

BACKGROUND: The effects of NaCl and CaCl₂ on the solubility and emulsifying properties, namely emulsifying activity index (EAI) and emulsion stability index (ESI) of sweet potato proteins (SPPs) at pH 1–10, were investigated. RESULTS: At lower NaCl (0.1 mol L^?1) and CaCl₂ (0.05 mol L^?1) concentrations, the solubility profiles of the SPPs were very similar to those in distilled water, and the lowest solubility occurred at pH 4. Increased NaCl and CaCl₂ concentration resulted in lower SPP solubility in most of the pH studied (P < 0.05). At pH < 3, NaCl improved the EAI of SPP while at pH > 7 it reduced the EAI of the SPP (P < 0.05). Moreover, addition of NaCl also resulted in reduction of ESI of the SPP in most of the pH studied (P < 0.05). On the other hand, the presence of 0.2 mol L^?1 CaCl₂ rendered the EAI and ESI of the SPPs independent of the influence of pH. CONCLUSION: The present studies show that pH and salts modified the emulsifying properties of the SPPs, and CaCl₂ at a certain concentration could be used to improve the emulsifying properties of the protein. Copyright © 2008 Society of Chemical Industry     

超声处理辅助大豆分离蛋白改善蛋黄乳化性

蛋黄(Egg yolk,EY)的乳化特性易受加工因素影响,为了改善其乳化性能,采用大豆分离蛋白(Soy protein isolate,SPI)辅以超声处理,探究不同超声功率对大豆分离蛋白改善蛋黄乳液乳化性及蛋黄蛋白性能的影响.结果 表明:在EY中添加SPI,可以显著提高EY的乳化活性(Emulsifying acti...     

Isolation of peanut protein aggregates using aqueous extraction processing combined with membrane separation

A two-stage microfiltration and ultrafiltration (MF/UF) for peanut protein recovery and water recycling from aqueous extraction processing (AEP) were investigated. Peanut protein aggregates and alkaline water were obtained using flat and wound MF/UF and alkaline water recycled in AEP. With this approach, most of the wastewater could be recycled to produce reusable water to solve wastewater problems in aqueous oil extraction processing from oilseeds. The result showed that a little oil and protein were lost (1.21% and 4.35%, respectively) during the recycling of permeate in AEP, which was still acceptable. Peanut protein aggregations (PPAs) were characterised by analysis with Fourier-transform infrared spectroscopy (FTIR), sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS-PAGE), high-performance gel filtration chromatography (HPGFC) and binding force analysis. Solubility analysis suggested that PPA had molecular structures with more hydrophobic groups on the surface than in the peanut protein isolate (PPI). In vitro, PPA was digested by both pepsin and trypsin more than PPI. FTIR profiles demonstrated there were more β-sheet and less α-helix in PPA, which means much more aggregation. In addition, binding force analysis showed hydrophobic interaction was the major force that restricted dissolution of PPA and disulfide bonds were of second importance, which provided a possible physical treatment opportunity for improving the solubility of PPA.     

挤压温度对挤压大米蛋白与葡萄糖复合物功能和结构特性的影响

为获得一种快速、有效的工业化生产方法,本研究在大米蛋白与葡萄糖发生美拉德反应前对大米蛋白进行挤压改性。大米蛋白在不同温度（80、90、100、110、120、130 ℃）下挤压,然后在pH 10.5条件下与葡萄糖接合30 min。分析不同挤压温度对其功能性质（溶解度、乳化活性和乳化稳定性）的影响,利用扫描电子显微镜、傅里叶变换红外光谱和十二烷基硫酸钠-聚丙稀酰胺凝胶电泳对挤压后的大米蛋白和葡萄糖复合物进行结构表征。结果表明：与天然大米蛋白质和葡萄糖（native rice protein and glucose,NRPG）复合物相比,挤压大米蛋白和葡萄糖（extruded rice protein and glucose,ERPG）复合物在90 ℃的糖基化程度最高。与NRPG相比,ERPG（90～120 ℃）的溶解度降低,ERPG（80～90 ℃）的乳化活性、乳化稳定性和表面疏水性升高,而100～130 ℃的时候缓慢降低。红外光谱结果表明,与NRPG相比,ERPG具有较高的α-螺旋、β-转角和无规卷曲,β-折叠结构相对含量较低。十二烷基硫酸钠-聚丙稀酰胺凝胶电泳显示蛋白质通过挤压聚合成更大的颗粒。扫描电子显微镜显示,ERPG具有更多的无序结构和不规则碎片。     

棉籽蛋白功能特性的研究

考察了棉籽浓缩蛋白、沉淀蛋白和溶解蛋白3种棉籽蛋白的氮溶指数、吸水性、吸油性、起泡性与泡沫稳定性、乳化性与乳化稳定性等功能特性。结果表明,棉籽溶解蛋白的乳化性和起泡性较佳;棉籽浓缩蛋白和沉淀蛋白,除吸油、吸水能力强之外,其他的功能特性均较差。在吸水性方面,棉籽蛋白的吸水性要低于菜籽沉淀蛋白,但高于大豆沉淀蛋白。在吸油性方面,棉籽蛋白均低于菜籽蛋白和大豆蛋白。