菜籽抗氧化肽WDHHAPQLR的环境稳定性研究

本实验以DPPH·自由基清除活性、Fe~(2+)-螯合金属离子能力为指标来考察温度、酸碱度、食品配料成分、金属离子、防腐剂和人工胃肠液等环境因素对菜籽抗氧化肽(WDHHAPQLR)稳定性的影响。结果表明:随着温度的升高,抗氧化肽的活性逐渐降低,但还是保持在较高水平,但是当温度高于60℃时,菜籽抗氧化肽的活性显著降低,温度为100℃时,Fe~(2+)-螯合金属离子能力活性保持率仅在30%左右。强酸和强碱环境对抗氧化肽的稳定性影响较大,当溶液的pH值在6.0～8.0范围内时,活性较为稳定。抗氧化肽溶液的活性随着食盐浓度的增大而有所降低,当食盐的浓度达到8%时,抗氧化肽的活性保持率为86.33%。蔗糖质量分数在2%～8%范围内时,菜籽抗氧化肽的活性随蔗糖含量的增加而显著下降,在蔗糖质量分数达到8%,活性保持率在80%以上。在0.02%～0.16%质量分数范围内,柠檬酸对菜籽抗氧化肽的活性影响不大,其活性保持率均在90%以上。常见的金属离子对菜籽抗氧化肽的稳定性影响不一,Cu~(2+)和Zn~+对菜籽抗氧化肽的DPPH·自由基清除活性和亚铁离子螯合能力的影响最为显著。苯甲酸钠和山梨酸钾对抗氧化肽的稳定性影响不明显,可以在多肽产品中作为防腐剂使用;菜籽抗氧化肽溶液经过胃蛋白酶消化后抗氧化活性显著增加,再经过胰蛋白酶消化后活性大幅度下降。     

蛋清肽的工艺优化、抗氧化作用及特性

以对DPPH自由基清除率为考察指标,筛选适宜蛋清肽制备蛋白酶。研究酶活、温度、蛋清含量及pH值对蛋清肽清除DPPH自由基的影响,利用正交试验探讨制备蛋清抗氧化肽的最佳工艺;以抗坏血酸(VC)为对照,研究蛋清肽总还原力大小、对羟自由基、超氧阴离子自由基的清除作用及对脂质过氧化的抑制作用;研究蛋清肽的部分特性。结果表明:风味蛋白酶适宜蛋清肽的制备,酶解时间选择90 min。最佳工艺为:pH 5,45℃,蛋清体积分数8%,酶活1 125 U。此条件下对DPPH自由基清除率为53.273%。蛋清肽对羟自由基(0.308 4～1.542 mg/mL)、超氧阴离子自由基(0.089～0.443 mg/mL)具有一定的清除能力,清除率随其质量浓度的增大而增加,且具有一定的还原力。对羟自由基,VC的IC50=0.092 mg/mL,蛋清肽IC50=1.24 mg/mL,对超氧阴离子自由基,VC的IC50=0.021 6 mg/mL,蛋清肽的IC50=0.054 mg/mL。在0.667～10.667 mg/mL范围内,蛋清肽对脂质过氧化的抑制作用随其质量浓度增加而减小,在0.667～10.667μg/mL范围内反而具有促进脂质过氧化作用。蛋清肽等电点在pH 3左右,其对羟自由基清除率随温度增加逐渐下降;在pH 2～10范围内,其溶解度几乎成线性增加。     

苦荞抗氧化肽AFYRW稳定性研究

为研究苦荞抗氧化肽AFYRW在生产加工、胃肠消化中的稳定性以及细胞毒性,以羟自由基(·OH)清除率和DPPH自由基清除率作为评价指标,研究pH值、温度、反复冻融、金属离子以及胃肠消化对苦荞抗氧化肽AFYRW体外抗氧化活性的影响,以红细胞溶血率评价细胞毒性。结果表明:高温、反复冻融、Na+、Mg²⁺对抗氧化肽AFYRW的抗氧化活性无显著影响;Ca²⁺会降低抗氧化肽AFYRW的DPPH自由基清除率,K+会提高抗氧化肽AFYRW的·OH清除率;体外模拟胃肠消化后或者pH值升高都会降低抗氧化肽AFYRW的抗氧化活性;苦荞抗氧化肽AFYRW对红细胞无溶血作用。综上苦荞抗氧化肽AFYRW具有良好的抗氧化活性,对红细胞无溶血作用,在生产和储存过程中,应避免过碱、接触Ca²⁺。     

加工条件对大黄鱼鱼肉抗氧化肽功能特性的影响

研究了不同加工条件下大黄鱼鱼肉抗氧化肽的溶解性、吸水性、持水性、吸油性、表观黏度、乳化能力、起泡性等功能特性。结果表明,大黄鱼鱼肉抗氧化肽的等电点处于pH 4.0左右,该pH值条件下,抗氧化肽的溶解性和乳化性表现为最低,而乳化稳定性、起泡性及泡沫稳定性最高。此外,大黄鱼抗氧化肽展现了良好的吸水性、吸油性和流动性,但持水性相对较差。大黄鱼鱼肉抗氧化肽可作为一种生产功能性食品的潜在添加剂。     

茶多酚与大豆分离蛋白对复合乳化体系性质的影响

采用单因素试验研究了茶多酚(TP)添加量、pH值、油添加量、大豆分离蛋白(SPI)浓度对TP-SPI复合乳液的乳化活性、稳定性和抗氧化性等性质的影响,为制备不同需求的复合乳化体系条件选择提供理论依据。研究表明:随着TP添加量的增加,复合乳液的乳化稳定性和抗氧化性增强,对乳化活性影响不显著;随着油量的增加,复合乳液的乳化活性和抗氧化性降低,乳化稳定性先增强后降低;随着pH值的增加,复合乳液的乳化活性和稳定性先降低后增强,其乳化活性和乳化稳定性在碱性条件下比在酸性条件下强,抗氧化能力变化则与之相反;随着SPI的浓度增大,复合乳液的乳化活性和乳化稳定性增强,对抗氧化性的影响不显著。     

不同加工工艺乳饼抗氧化肽稳定性研究

为研究不同加工工艺乳饼抗氧化肽的稳定性,以传统乳饼（TRB）和发酵型乳饼(FRB)为实验材料,超滤分离出不同分子量（3～10 ku和<3 ku）乳饼蛋白肽,以ABTS、DPPH自由基清除率、还原能力RP为评价指标,考察温度、pH、食品原辅料、压力等加工环境和模拟胃肠消化对不同工艺乳饼抗氧化活性的影响。结果表明,不同加工环境及模拟胃肠消化后,不同分子量的FRB抗氧化肽稳定性高于TRB,且3～10 ku的FRB抗氧化肽活性最高;FRB和TRB抗氧化肽在高温和酸碱环境中活性显著下降（P<0.05）;山梨酸钾和超高压加工技术对乳饼抗氧化活性影响不显著;高糖抑制抗氧化活性,但分子量3～10 ku的FRB蛋白肽DPPH·清除率任能维持在84%以上;2%～8%的NaCl有利于提高抗氧化活性。胃肠消化后,不同工艺乳饼蛋白肽DPPH自由基清除活性显著降低（P<0.05）,ABTS·清除率、还原能力显著升高（P<0.05）,其ABTS·清除率高于41.85%,还原能力RP值大于0.12。研究可为乳饼及其抗氧化肽的加工利用提供理论依据。     

添加物和体外模拟胃肠道消化对鸢乌贼抗氧化肽稳定性的影响

以鸢乌贼抗氧化肽为研究对象,以DPPH自由基、羟自由基(·OH)清除能力和还原力为评价指标,探究了蔗糖、海藻糖、柠檬酸、NaCl、防腐剂、金属离子以及人工模拟胃肠道消化对其抗氧化活性的影响。结果表明:蔗糖和海藻糖对鸢乌贼抗氧化肽的抗氧化活性无显著性改变;柠檬酸和NaCl在一定的浓度范围内能起到增效作用,使鸢乌贼抗氧化肽的抗氧化活性增加;防腐剂(山梨酸钾和苯甲酸钠)对鸢乌贼抗氧化肽的抗氧化稳定性影响不明显;Cu~(2+)、Zn~(2+)使鸢乌贼抗氧化肽的抗氧化活性随着浓度增加显著性降低,Mg~(2+)、Ca~(2+)和K~+对鸢乌贼抗氧化肽的抗氧化活性影响较小;而人工模拟胃肠道消化表明,胃肠道消化不利于保持鸢乌贼抗氧化肽的抗氧化稳定性。     

燕麦发芽过程中肽的变化及其相关特性研究

目的:研究燕麦发芽过程中肽及其生物活性的变化规律,考察燕麦肽的稳定性。方法:以清除1,1-苯基-2-苦肼基自由基(DPPH)和2,2-联氮-3-乙苯-二噻唑-6磺酸(ABTS)产生的自由基能力及铁还原力评价其抗氧化活性,以抑制血管紧张素转化酶(ACE)活性,评价其降血压活性。结果:发芽过程中,燕麦肽含量及其抗氧化和降血压活性均呈增加的趋势。燕麦肽溶解性和ACE抑制活性在不同程度上受到pH、温度和消化酶的影响。结论:发芽可有效富集燕麦肽的含量,提高燕麦抗氧化能力和ACE抑制活性。     

罗非鱼皮/鳞胶原蛋白肽加工性能及抗氧化性质比较研究

为探究企业提供的5种不同标称分子量的罗非鱼鱼皮和鱼鳞胶原蛋白肽的加工性能及其抗氧化活性,对几种胶原蛋白肽产品的吸湿性、吸油性、乳化性、起泡性、还原力、超氧阴离子自由基(O2-·)以及羟自由基(·OH)清除效果进行了系统的研究比较。结果表明,采用凝胶渗透色谱(gel permeation chromatography,GPC)测得标称分子量为1、3、5 k Da罗非鱼鱼皮胶原蛋白肽的重均相对分子质量分别为823、1 196、2 753 Da,标称分子量为3、5 k Da罗非鱼鱼鳞胶原蛋白肽重均相对分子质量分别为1 189、1 926 Da;标称为5 k Da的鱼鳞肽吸湿性最强,为0.26 g/g;标称为1 k Da的鱼皮肽吸油性最强,为2.57 m L/g;标称为5 k Da的鱼鳞肽乳化性最强,达到51.8%,5 h内乳化稳定性最优;5种产品的起泡性很接近,在165%~170%之间;60 min内,5 k Da的鱼皮肽和鱼鳞肽起泡稳定性均较好;以铁氰化钾还原法、超氧阴离子自由基(O2-·)和羟自由基(·OH)法对5种肽产品的抗氧化性进行分析显示,肽产品3种抗氧化能力均随样品浓度增大而增强;肽产品的还原力和O2-·清除效果略差于维生素C,5种产品中标称为1 k Da鱼皮肽的还原力最佳,标称5 k Da罗非鱼鱼鳞肽O2-·清除能力最佳;而标称3 k Da和5 k Da的罗非鱼鱼鳞胶原蛋白肽对羟自由基(·OH)的清除效果则比维生素C显优,其中5 k Da的鱼鳞肽对羟自由基(·OH)的清除效果最高达到84%;肽产品的抗氧化性与肽的分子量和来源有密切关系。研究表明,5种肽产品的标称分子量与实际分子量均有一定的差异,但具有良好的加工性和较好的抗氧化性,研究结果可为这5种肽的进一步开发利用提供支持。     

鲨鱼肉酶解物的抗氧化作用及其稳定性研究

以还原能力和金属离子螯合能力、清除DPPH·、O2-·、OH·自由基能力为指标,考察鲨鱼肉酶解物的抗氧化活性,同时以清除自由基DPPH·的活性为指标,分析温度和pH值对其抗氧化作用稳定性的影响。结果表明:鲨鱼肉酶解液产物具有一定的还原能力和金属离子螯合能力,其清除DPPH·、O2-·、OH·自由基的IC50值分别为10.16、23.71、19.82mg/mL。酶解产物耐热性强;在酸性环境中,鲨鱼肉酶解液能较好地保持其抗氧化活性,但在碱性环境中抗氧化活性丧失较快。     

干燥方式对蛋清蛋白理化性质和功能特性的影响

为探究干燥方式对蛋清蛋白（egg white protein,EWP）功能特性的影响及其内在机理,分别通过喷雾干燥与真空冷冻干燥制备蛋清蛋白粉,并对其蛋白结构、理化性质与功能特性进行研究。结果表明,与蛋清液（EWP-C）相比,喷雾干燥使蛋清蛋白（EWP-P）的内源性荧光强度降低,表面疏水性和表面游离巯基含量增大。傅里叶变换红外光谱分析显示,EWP-P的α-螺旋、β-折叠和β-转角分别为16.30%、25.72%和40.23%,冷冻干燥蛋清蛋白（EWP-D）分别为20.43%、24.32%和35.69%。不同pH下,EWP-D的溶解度均高于EWP-P,表面张力小于EWP-P。此外,EWP-P的接触角为99.62°,高于EWP-D（接触角为65.97°）,表明喷雾干燥能显著提高蛋白的疏水性（P<0.05）。EWP-D在不同pH下的乳化性、乳化稳定性以及起泡性均大于EWP-P,但起泡稳定性更小,这与EWP-D较高的溶解性与较低的表明疏水性有关。荧光倒置显微镜及激光共聚焦扫描显微镜分析表明EWP-D乳液的微粒更小,分布更均匀,其稳定性高于EWP-P。综上,喷雾干燥蛋清蛋白的β-折叠结构较多,表面游离巯基含量和表面疏水性较高,具有较好的凝胶性;冷冻干燥蛋清蛋白的表面疏水性较小,且表面张力小、溶解度大,具有更好的乳化能力与起泡性。     

Structural characterization and functional properties of egg white protein treated by electron beam irradiation

This study investigated the functional properties and structural characteristics of egg white protein (EWP) powder treated by electron beam irradiation (EBI) at the doses of 5, 10, 20, 30, 50, 70 and 100 kGy. In comparison with the untreated sample (0 kGy), the EBI-induced EWP showed generally better solubility and higher antioxidant capacity by ABTS•⁺ radical scavenging assay. Furthermore, the emulsifying activity index of EBI-induced EWP increased with increased EBI dose, reaching the maximum value of 15.8 ± 0.4 m²/g at 100 kGy. The emulsifying stability index and ϛ-potential of EBI-induced EWP showed fluctuating tendencies. These functional property changes of protein were attributed to the conformational changes caused by EBI. SDS-PAGE patterns confirmed that high-dose EBI would result in protein depolymerization to low-mass molecules at 11 kDa, contributing to the increased solubility. Circular dichroism data demonstrated that EBI-induced EWP exhibited partial denaturation and a flexible structure, which was responsible for the improved emulsifying properties. Fluorescence spectra revealed that high EBI doses led to an increase in the polar environment around tryptophan, which could enhance the solubility and antioxidant activity of EWP. In addition, high EBI doses decreased the content of free and total sulphydryl groups, and changed the intermolecular forces of protein, including ionic bonds, hydrogen bonds, hydrophobic interactions, and disulfide bonds. These findings can provide solid support for practical applications of EBI technology in EWP food processing.     

Novel Radiofrequency‐Assisted Thermal Processing Improves the Gelling Properties of Standard Egg White Powder

Effect of radiofrequency (RF)‐assisted thermal processing on quality and functional properties of high‐foaming standard egg white powder (std. EWP, pH approximately 7.0) was investigated and compared with traditional processing (heat treatment in a hot room at 58 °C for at least 14 d). The RF‐assisted thermal treatments were selected to meet the pasteurization requirements and to improve the functional properties of the std. EWP. The treatment conditions were: RF heating to 60, 70, 80, and 90 °C followed by holding in a hot air oven at those temperatures for different periods ranging from 4 h at 90 °C to 72 h at 60 °C. The quality (color and solubility) and functional properties (foaming properties: foaming capacity and foam stability; and gelling properties: water holding capacity and gel‐firmness) of the std. EWP were investigated. RF‐assisted thermal processing did not affect the color and solubility of std. EWP at any of the treatment conditions. In general, the foaming and gelling properties of RF‐assisted thermally processed std. EWP increased with an increase in temperature and treatment duration. The optimal RF‐assisted treatment conditions to produce std. EWP with similar functional properties as the traditionally processed (hot room processed) std. EWP were 90 °C for ≥8 h. These optimal conditions were similar to those for high gel egg white powder (HG‐EWP, pH approximately 9.5). The RF‐assisted thermal pasteurization improved the gelling properties of std. EWP to the levels of HG‐EWP, leading to newer applications of this functionally improved safe product. The RF‐assisted thermal processing allows the processor to produce a HG‐EWP from std. EWP subsequent to processing while simultaneously pasteurizing the product, thus assuring the product safety.     

蛋清蛋白/苹果多酚提高多糖基可食性包装薄膜性能及在腰果贮藏保鲜中的应用

海藻酸钠（sodium alginate,SA）、κ-卡拉胶（κ-carrageenan,κ-C）具有天然无毒、成膜性好的特点,常被用于制备可食用多糖基包装膜。但多糖薄膜具有亲水性强、机械性能差、抗氧化活性低等缺陷。本实验以SA、κ-C为复合多糖成膜基质,以乳酸钙为交联剂,并添加蛋清蛋白粉（egg white powder,EWP）增强多糖薄膜综合包装性能,添加苹果多酚（apple polyphenol,AP）作为抗氧化剂赋予薄膜抗氧化功能。通过傅里叶变换红外光谱、X射线衍射、扫描电子显微镜、紫外吸收光谱等方法分析各组分基团间相互作用,并对腰果仁进行包装贮藏保鲜实验。结果表明：本研究制备的多糖基可食用包装薄膜具有较好的综合包装性能和突出的抗氧化性能。与SA/κ-C薄膜相比,Ca2＋的交联使可食性薄膜的机械性能、阻隔性能显著提升。在最优添加量下,添加EWP使薄膜断裂延伸率由7.99%提高至20.81%,水蒸气渗透率降低了28.84%,氧气渗透率降低了27.07%;加入AP后,可食性薄膜抗张强度由18.58 MPa提升到30.23 MPa,水蒸气渗透率降低了42.35%,氧气渗透率降低了34.13%,同时薄膜阻光性能显著提升。此外,AP/EWP/SA/κ-C可食性薄膜包装降低了腰果仁贮藏期间的水分活度、水分质量分数、过氧化值和酸价,能有效抑制腰果仁的氧化酸败。结论：研究可为多糖/蛋白质基可食性复合包装薄膜的制备及应用提供参考。     

Comparison of the effect of hydrodynamic and acoustic cavitations on functional,rheological and structural properties of egg white proteins

The impacts of hydrodynamic cavitation (HC) (orifice plate-2 mm) and acoustic cavitation/ultrasound (US) (probe sonicator- 50% amplitude; 20 kHz frequency) on the functional (foaming, gelling, emulsifying), physicochemical (solubility), rheological and structural properties of egg white proteins (EWP) were evaluated. The egg white solutions were treated for 5, 10 and 15 min for both HC and US. The results suggested that HC-treated samples had higher impact on physiochemical and functional properties when compared to US-treated samples. The best foaming, emulsifying and gelling property was obtained for HC-treated samples (15 min treatment time). Both cavitation treatments exhibited shear thinning behavior, among which US-treated samples had the lowest viscosity. HC-treatment applied for 15 min provided the highest in vitro digestibility (75.51 ± 0.126%) among all the samples. The FTIR spectra of EWP exhibited similar backbone structure for all the samples, while the secondary structure obtained from deconvolution of Amide-I peak differed significantly. Moreover, for product development with EWP, HC -treated samples were more appropriate in gelling and emulsifying applications, which can ensure quality products with higher in vitro digestibility. Overall, this study indicated that HC treatment (for 15 min) improved the functional, rheological, and structural properties of EWP.     

鸡蛋清蛋白水解物的物化及功能性质的研究

蛋清蛋白质溶解性欠佳且容易起泡,使其应用受限。本文利用Alcalase酶解鸡蛋蛋清蛋白制取水解度为5~15%的酶解物并对酶解物的理化性质和功能性质进行了表征。测定性质包括乳化性、起泡性及稳定性以及溶解性、表面疏水性。所有酶解产物具有较低的表面疏水性,水解大大提高了溶解度,当水解度15%时最大值为89%,但乳化性有所降低,起泡性及稳定性也大约下降了40%。     

Impact of pH on the interactions between whey and egg white proteins as assessed by the foamability of their mixtures

The impact of protein–protein interactions on foaming properties of mixtures consisting of egg white proteins (EWP) and whey proteins (WP) with total protein content of 60 g/L was examined at pH 5, 7 and 9. The ratio between EWP and WP in the mixtures was varied between 67:33, 50:50 and 33:67 (in %; w/w). The ionic strength was adjusted to that of milk (I = 176 mM). The foamability of the protein products was characterized by the foam capacity, stability and firmness. In addition, the hydrophobicity in the protein solutions was assessed as a measure for the physical behaviour and ability of proteins to adsorb at the air–water interface.The individual egg white proteins and whey proteins each showed the best foaming properties at pH 5 and pH 9, respectively. At pH 9 a synergism was observed in the capacity and stability of the foams from EWP/WP-mixtures. This effect appears to be caused by the electrostatic interactions between egg white and whey proteins which occur in the bulk solution after the pH adjustment prior to the foaming. In contrast, at pH 5 no positive influence of foaming the components in a mixture as well as no indication of intermolecular interactions was found. At pH value near the pI of ovalbumin the protein interactions occur when the proteins have adsorbed at the air–water interface. The protein systems foamed at pH 7 showed intermediate foamability compared to the values obtained at alkaline and acidic pH.     

Effect of high‐pressure treatment on trypsin hydrolysis and antioxidant activity of egg white proteins

High‐pressure processing (HPP) is known to modify the functional properties of the proteins by changing its structure that can lead to protein denaturation, aggregation or gelation, depending on the protein system and the applied pressure. The potential to modify functional properties of protein and their products using HPP has been explored widely in last decade. In this study, the effect of HPP on the degree of trypsin hydrolysis (DTH) and antioxidant activity (AA) of egg white protein (EWP) and freeze‐dried egg white powder (DEW) was evaluated. EWP and DEW were subjected to trypsin hydrolysis for up to 120 min, with and without HP treatments [pressure level (350–550 MPa) and treatment time (5–15 min)]. HP treatment caused substantial increase in DTH of EWP and DEW, increasing it from 2.78% (EWP control) and 2.20% (DEW control) to 11.3% (HP‐treated EWP) and 8.41% (HP‐treated DEW), respectively. HP treatment also had an emphatic effect on AA of EWP (concentration 10% w/v) with AA increasing from 9.34% for control EWP to 19.0% after 5‐min HP treatment at 350 MPa and 25.00% after the same treatment at 550 MPa. Overall, HPP caused an increase in DTH and AA of EWP and DEW over the control. SDS‐PAGE and differential scanning calorimetric studies confirmed the effect of HP on the hydrolysis of egg proteins.     

胃蛋白酶水解大米蛋白的研究

采用胃蛋白酶对大米蛋白进行水解以改善其功能性质。结果表明,酶添加量7U/g(以蛋白质干基计)、pH1.5、时间5h、温度30℃时,胃蛋白酶对大米蛋白溶解性有较好的改善作用。水解后大米蛋白的乳化稳定性与乳化性分别为33.28min、0.456,高于大豆蛋白和鸡蛋清蛋白;起泡性和起泡稳定性比未经过任何处理的大米蛋白分别提高了25.0%、82.4%;持水性和持油性为2.80、3.30g/g,是未经处理的大米蛋白的2.09、2.92 倍。     

Improvement of antioxidant activity of egg white protein by phosphorylation and conjugation of epigallocatechin gallate

Egg white protein (EWP) was phosphorylated by dry heating in the presence of pyrophosphate. The antioxidant activity of phosphorylated EWP (PP-EWP) was then investigated before and after conjugation of epigallocatechin gallate (EGCG). The binding interaction between EWPs and EGCG was investigated by UV and FTIR, which indicated that more EGCG bound to PP-EWP than to native EWP and dry-heated EWP. The antioxidant activities including ABTS⁺ free-radical scavenging capacity, oxygen radical antioxidant capacity, reducing power, chelating capacity, and superoxide anion scavenging activity of EWP were remarkably improved by phosphorylation before and after conjugation of EGCG. The improved antioxidant property of PP-EWP can be attributed to the introduced phosphate group, more exposed hydrophobic group, increased surface thiol group of protein, and more EGCG bound to EWP. The secondary structure of PP-EWP decreased with more bound EGCG. This study is the first to describe an improvement in the antioxidant property of EWP by phosphorylation and conjugation of EGCG, thereby providing insight into the design of food protein antioxidant.