Influence of particle size and ionic strength on the freeze-thaw stability of emulsions stabilized by whey protein isolate

The influence of particle size and ionic strength on the freeze-thaw(FT) stability of emulsions stabilized by whey protein isolate(WPI) was investigated in this study. The destabilization of emulsions during the FT process could be suppressed in a way by decreasing the particle size of the initial emulsions, which was the result of retarding the coalescence between oil droplets. To further improve the FT stability of emulsions, different amounts of Na Cl were added before emulsification. The emulsions with the ionic strength at 30–50 mmol/L exhibited good FT stability. Notably, the ionic strength in this range would not lower the freezing point of emulsions below the freezing temperature used in this study. Salt addition could improve the structural properties of proteins, which was available to strengthen the rigidity and thickness of interfacial layers, sequentially building up the resistance that the destruction of ice crystals to emulsions. Moreover, stronger flocculation between emulsion droplets could promote the formation of a gel-like network structure dominated by elasticity in the emulsion system, which might effectively inhibit the movement of droplets, and improve the FT stability of emulsions eventually. The result was of great significance for the preparation of emulsion-based foods with improved FT stability.

Effect of sodium starch octenyl succinate-based Pickering emulsion on the physicochemical properties of hairtail myofibrillar protein gel subjected to multiple freeze-thaw cycles

A Pickering emulsion based on sodium starch octenyl succinate(SSOS)was prepared and its effects on the physicochemical properties of hairtail myofibrillar protein gels(MPGs)subjected to multiple freeze-thaw(F-T)cycles were investigated.The whiteness,water-holding capacity,storage modulus(G')and texture properties of the MPGs were significantly improved by adding 1%-2%Pickering emulsion(P<0.05).Meanwhile,Raman spectral analysis demonstrated that Pickering emulsion promoted the transformation of secondary structure,enhanced hydrogen bonds and hydrophobic interactions,and promoted the transition of disulfide bond conformation from g-g-g to g-g-t and t-g-t.At an emulsion concentration of 2%,theα-helix content decreased by 10.37%,while theβ-sheet content increased by 7.94%,compared to the control.After F-T cycles,the structure of the MPGs was destroyed,with an increase in hardness and a decrease in whiteness and water-holding capacity,however,the quality degradation of MPGs was reduced with 1%-2%Pickering emulsion.These findings demonstrated that SSOS-Pickering emulsions,as potential fat substitutes,can enhance the gel properties and the F-T stability of MPGs.

Desalted duck egg white nanogels as Pickering stabilizers for food-grade oil-in-water emulsion

Achieving the reuse of traditional egg by-products,salted duck egg whites(SEW),is an urgent problem to be solved.In this current work,we constructed a heat-induced gel-assisted desalination method for SEW.Subsequently,a top-down way was utilized to prepare desalted duck egg protein nanogels(DEPN)with uniformly distributed diameters and their application in the oil/water(O/W)interface system was explored.The results revealed that the increase of DEPN concentration could lower the droplet size,however,the size was negatively correlated with the oil phase fraction.Moreover,the effect of pH,ionic strength,and temperature on the emulsion stability demonstrated that the DEPN-stabilized emulsion displayed superior physical stability under different conditions.The addition of NaCl resulted in the significant decrease in droplet size of the emulsion,while further increasing the NaCl concentration,the droplet size did not decrease accordingly.Besides,heat-treatment and cold-treatment had little negative effect on the stability of the emulsion.Even if the droplet size of the emulsion increased at 80℃for 3 h,the morphology of the emulsion remained unchanged.Our study demonstrated DEPN had great potential as a stabilizer for food-grade Pickering emulsions.

Characteristics,formation mechanism and stability of high internal phase emulsions stabilized by porcine plasma protein (PPP) / carrageenan (CG) hybrid particles

High internal phase emulsions (HIPEs) stabilized by nanoparticles based on biomacromolecules are challenging issues in recent decade.Herein,a newly developed HIPE was investigated by using heat-denatured porcine plasma protein (PPP) nanoparticles at pH 6.5 as emulsifier,and its emulsifying stability could be significantly enhanced by compounding carrageenan (CG).In the miscible system,PPP and CG formed hybrid particles through non-covalent interaction,and the sizes and zeta-potentials of the particles increased significantly along with addition of CG (from 0 to 0.7%,w/v),reached up to about 3.6 μm and −53 mV at 0.5% (w/v),respectively.CG weakened the ability of PPP to lower interfacial tension of oil/water (O/W),but increased the apparent viscosity of the system.The results from CLSM,rheology and stability experiments indicated a significant increasing trend of the HIPEs stability and solid-like characteristics along with addition of CG.Compared with the controls including bovine serum albumin (BSA),BSA-CG and CG alone,PPP-CG hybrid particles had good performance in fabricating and stabilizing the HIPEs.The work revealed the novel function of PPP as emulsifier of HIPEs and so offered the theoretical direction for application of PPP as a mass by-product,as well as an excellent HIPEs system for food,medicine and cosmetics fields.

Combination of microwave heating and transglutaminase cross-linking enhances the stability of limonene emulsion carried by whey protein isolate

In this study,we examined the effect of transglutaminase(TG)cross-linking time(0 h,2 h,4 h,8 h,and 12 h)on the stability of limonene emulsion loaded by microwave-heated WPI(MWPI).Size exclusion chromatography results showed that molecular weight of TG-treated MWPI and WPI was enhanced with the increase in TG cross-linking time(0–12 h).Microwave and TG cross-linking decreased particle size(7.55%)and increasedζ-potential(5.33%)and protein adsorption(4.58%)of WPI emulsion at TG cross-linking time of 12 h.CLSM results showed smaller droplet size of MWPI-TG emulsion and its uniform size.The obtained limonene emulsion loaded by MWPI-TG at 12 h showed the lowest creaming index and the strongest oxidative stability under aerobic conditions after 10th days of storage.Thus,the combination of microwave heating and TG cross-linking effectively enhanced the stability of limonene emulsion stabilized by WPI and facilitating the application of WPI in the fields of food,medicine,cosmetics,and other areas.

大豆分离蛋白对大豆肽纳米颗粒Pickering乳液性能的影响

为提高大豆肽纳米颗粒(SPN)Pickering乳液稳定性,以大豆肽聚集体为原料,采用超声法制备SPN,对超声时间进行了优化;在SPN体系中引入大豆分离蛋白(SPI)构建复合乳化剂,研究不同乳化剂质量浓度下SPI对SPN界面活性和乳化稳定性的影响。结果表明:选取超声时间10 min制备SPN;随着乳化剂质量浓度的增大,乳液粒径逐渐减小,当乳化剂质量浓度较低(5 mg/mL)时,乳液出现桥联,乳化剂质量浓度过高(30 mg/mL)时则出现絮凝;界面蛋白吸附率随着乳化剂质量浓度的增加呈现先升高后降低的趋势。在相同乳化剂质量浓度下,添加SPI的SPN乳液(SPI-SPN乳液)的粒径分布峰左移,其粒径、界面蛋白吸附率显著小于SPN乳液的;在储存过程中,SPN乳液粒径逐渐增大,SPI-SPN乳液粒径没有显著变化;SPI-SPN乳液的乳析指数小于相同乳化剂质量浓度的SPN乳液,当乳化剂质量浓度为30 mg/mL时,储存15 d SPI-SPN乳液未出现分层现象。综上,SPI可以提高SPN的界面活性和SPN乳液储存过程中的絮凝稳定性和分层稳定性。

植物蛋白内禀性质对充气乳液稳定性的影响研究

植物蛋白基充气乳液是茶饮、咖啡市场发展的重要功能性配料,打发后可作为奶盖、奶霜和雪顶等。但这类充气乳液易失稳,主要原因是植物蛋白的使用功能性通常欠佳,其稳定充气乳液的机制尚不明晰。本研究以典型豌豆分离蛋白和大豆分离蛋白为研究对象,分析其结构特征和所制备充气乳液在储藏期的稳定性,揭示相应的稳定与失稳机制。结果表明,植物蛋白的溶解度、游离巯基含量和7S/11S比例是影响充气乳液稳定性的关键因素。低溶解度造成的低液相蛋白含量会增加脂肪球碰撞概率;游离巯基含量高会进一步促进液相蛋白和其他蛋白发生巯基与二硫键的交换,从而加快乳液絮凝和聚结;而11S蛋白可以增加蛋白膜的强度,降低充气乳液在制造过程中的失稳程度。

麦胚蛋白基姜黄素乳液的制备及其稳定性

利用小麦胚芽蛋白稳定的水包油乳液对姜黄素进行包埋,通过对乳液液滴粒径测定及微观结构的表征,考察麦胚蛋白浓度对乳液粒径以及乳液物理稳定性的影响,进一步研究贮藏过程及加热处理对乳液中姜黄素化学稳定性的影响。结果表明,随着乳状液中麦胚蛋白浓度的增加(0.5%~4.0%),乳液液滴的粒径从1.9μm降低至0.3μm,乳液的贮藏稳定性得到提高。高温处理对于乳液中姜黄素的稳定性影响较大。经80℃处理后,姜黄素含量明显下降,但麦胚蛋白浓度增加有利于提高乳液中姜黄素的热稳定性。小麦胚芽蛋白构建的姜黄素乳液体系具有较好的稳定性,其在功能性食品的加工中具有良好的应用潜力。

超声强化豌豆蛋白-高酯果胶复合物乳液稳定性研究

【目的】探讨超声对豌豆蛋白-高酯果胶复合物乳液稳定性的影响,为豌豆蛋白的开发利用提供参考。【方法】以豌豆蛋白(pea protein,PP)、高酯果胶(high methoxyl pectin,HMP)、超声豌豆蛋白(PP-US)和超声高酯果胶(HMP-US)制备的乳液为对照,比较豌豆蛋白-高酯果胶复合物(PP-HMP)和超声豌豆蛋白-高酯果胶复合物(PP-HMP-US)制备的乳液在储藏过程中粒径、Zeta-电位、微观结构、表观黏度和乳析指数的变化,结合复合物的油-水界面行为,阐明PP-HMP-US复合物的界面行为与其乳液稳定性的关系。【结果】与豌豆蛋白(PP)和超声豌豆蛋白(PP-US)乳液相比,豌豆蛋白-高酯果胶复合物(PP-HMP)和超声豌豆蛋白-高酯果胶复合物(PP-HMP-US)乳液的粒径和剪切稀化程度较小,Zeta-电位绝对值较大,储藏过程中液滴分布均匀且未出现乳析现象。与豌豆蛋白-高酯果胶复合物(PP-HMP)乳液相比,超声豌豆蛋白-高酯果胶复合物(PP-HMP-US)乳液的粒径和表观黏度进一步减小,储藏过程中乳液更为稳定。油-水界面行为研究结果表明,超声可以促进豌豆蛋白与高酯果胶结合,减小豌豆蛋白-高酯果胶复合物(PP-HMP)的接触角,且降低复合物界面张力的能力显著提高,更有利于PP-HMP-US乳液的稳定。【结论】超声可以减小豌豆蛋白-高酯果胶复合物(PP-HMP)的接触角,改善其油-水界面行为及乳液的理化特性,进而提高PP-HMP-US乳液的稳定性。

咖啡酸-葡聚糖-肌原纤维蛋白酶解物乳液稳定性的研究

为了探究咖啡酸(Caffeic Acid,CA)、葡聚糖(Dextran,DEX)复合修饰联合胰蛋白酶不完全酶解对于肌原纤维蛋白(Myofibrillar Protein,MP)乳化特性的提升效果,以CA-DEX-MP复合酶解物为乳液稳定剂制备乳液,优化稳定剂的添加剂量,并以原始MP和MP酶解物稳定的乳液为对照,评估乳液在不同环境刺激下的稳定性。结果表明,CA-DEX-MP酶解物添加量为3 wt.%时乳液具有较低的颗粒粒径(390.26 nm)、电位(-23.6 mV)和较高的界面蛋白吸附量(11.22 mg/mL),且均匀分布;流变性研究表明,该乳液体系显示出显著低于原始MP乳液的表观粘度,可有效避免乳液的相分离现象。3 wt.%CA-DEX-MP复合酶解物乳液在不同温度、酸碱、盐离子强度和28 d贮藏期下均表现出较优的稳定性,可实现乳液的稳定。最终结果表明,乳液稳定剂为3 wt.%CA-DEX-MP复合酶解物时,乳液拥有最高的稳定性。该研究可为肌原纤维蛋白在新型食品乳液稳定剂开发中的应用提供理论支撑和方法学指引。

精氨酸/低酯果胶对乳液热稳定性的影响

针对油脂蛋白多糖多重乳液体系在热力杀菌过程中因发生乳清蛋白变性团聚而引起的乳液不稳定现象,通过精氨酸(Arg)和低酯果胶(LMP)对蛋白胶束表面电荷和胶束结构的修饰作用,形成相应的精氨酸乳清蛋白复合物(Arg-whey protein complex,AWPC)和精氨酸乳清蛋白低酯果胶复合物(Arg-whey protein-low methoxyl pectin complex,AWPPC)。研究结果表明:通过Arg复合修饰、热力杀菌(121℃,15 min)后油脂蛋白多糖多重乳液体系的平均粒径减小39.1%,Zeta电位绝对值增加17.6%,乳化活性指数(EAI)提高18.7%,冻融和杀菌处理的冷热稳定性显著提高。当Arg和LMP的最佳质量比为0.15∶0.70时,AWPPC溶液的EAI达到最大值6.10 m 2/g。

高强度超声辅助乳化对金鲳鱼蛋白-茶皂苷复合乳液性质的影响

为提升金鲳鱼蛋白乳液的稳定性,改善金鲳鱼蛋白的功能特性,以金鲳鱼蛋白-茶皂苷复合物为乳化剂、大豆油为油相,采用高强度超声(HIUS)辅助乳化制备金鲳鱼蛋白-茶皂苷复合乳液,测定超声处理前后不同乳化剂与油相比例的金鲳鱼蛋白-茶皂苷复合乳液的乳化性、粒径分布、Zeta-电位、流变性、微观形态及贮藏稳定性。结果表明:与未超声处理金鲳鱼蛋白-茶皂苷复合乳液相比,超声处理后乳液的乳化活性指数和乳化稳定性指数总体增高,粒径减小,Zeta-电位的绝对值增加,流动指数升高,黏度系数降低,乳液液滴分布更均匀,乳液液滴更小,贮藏稳定性较好。综上,HIUS处理有助于改善金鲳鱼蛋白-茶皂苷的乳化性能。

Effect of small molecular surfactants on physical,turbidimetric,and rheological properties of Pickering nanoemulsions stabilized with whey protein isolate

In the present study,Pickering nanoemulsions(oil-in-water)co-stabilized with whey protein isolate(WPI)and three types of small molecular surfactants were prepared.Hexadecyltrimethylammonium(CTAB),sodium dodecyl sulfate(SDS),and Tween 20 were used as cationic,anionic,and nonionic surfactants,respectively.To investigate effects of small molecular surfactants on physical stability,turbidimetric,and rheological properties of protein-stabilized Pickering nanoemulsions,various treatments mimicking food processing including pH,heat,freeze-thaw,and salt were applied.Results revealed that the droplet size and polydispersity index of the nanoemulsion prepared with WPI alone were increased after heat treatment or at pH condition near the isoelectric point of WPI,indicating a low physical stability.However,nanoemulsions prepared with WPI-SDS or WPI-CTAB maintained their initial state even after heat treatment including autoclave.Furthermore,there was no significant change in the droplet size of the nanoemulsion prepared with WPI-Tween after freeze-thaw and salt treatments.Although Pickering nanoemulsion stabilized with both WPI and SDS had the highest viscosity,Turbiscan stability index(TSI)was the highest.However,the TSI of the nanoemulsions added with CTAB or Tween 20 was lower than that of the nanoemulsions prepared with WPI alone,confirming that the storage stability of protein-stabilized Pickering nanoemulsion was improved by adding small molecular surfactants.

肌原纤维蛋白稳定的Pickering乳液研究进展

肌原纤维蛋白(myofibrillar protein,MP)是肌肉中含量最高的一种两亲性蛋白,含有更全面的氨基酸,可作为固体颗粒乳化剂构建Pickering乳液。MP稳定的Pickering乳液具有稳定性高、制备经济、环境友好等优点,MP稳定Pickering乳液的作用机理及影响因素已成为当前的研究热点。本文主要综述MP稳定的Pickering乳液的作用机理、影响因素,以及其他食品组分(如多糖、氨基酸、抗氧化剂等)对乳液稳定性的影响。

热处理对金枪鱼蛋白乳液稳定性的影响

热处理是影响蛋白乳液稳定性的重要因素,本文研究了不同热处理温度(30、50、70、80、90℃,30 min)对金枪鱼蛋白乳液理化性能的影响。结果表明,与未进行热处理的样品相比,经过热处理的蛋白乳液乳化性能发生显著变化(P<0.05)。随着热处理温度的上升,金枪鱼蛋白乳液的表面疏水性、黏度、Zeta电位、乳化活性和乳化稳定性均呈现先增大再减小的趋势。加热温度在30~70℃范围内,蛋白二级结构展开,疏水性基团暴露,乳液黏度增大,液滴粒径减小,乳液稳定性增加;加热温度超过70℃后,蛋白分子重新聚集,与油滴结合的氨基酸残基重新进入蛋白质内部,液滴出现絮凝现象,乳液也变得不稳定。SDS-PAGE图谱显示70℃热处理30 min能够提升油-水界面蛋白质吸附量,液滴分布均匀,粒径达到最小值102.6 nm,黏度达到最大为43.87 Pa·s,贮藏28 d后没有出现乳析现象,乳液状态最稳定。综上,适当的热处理能提升金枪鱼蛋白乳液的稳定性。

蛋白多肽美拉德反应物稳定乳液的研究进展

乳液被认为是一种用于递送生物活性物质的良好体系,但由于其不稳定,极大地限制了应用。蛋白多肽具有独特的营养价值和生物活性,其结构灵活且易于在油水界面展开和重排,因此蛋白多肽稳定的乳液受到了广泛关注。蛋白多肽作为乳化剂虽然能够形成有效的乳液,但在稳定乳液方面效率较低。有研究发现蛋白多肽美拉德反应物稳定的乳液具有较好的稳定性、理化特性和功能特性。因此,本文对蛋白多肽美拉德反应物稳定乳液的作用机制、理化特性、功能特性、影响乳液稳定性的因素及其在递送体系中的应用进行了详细的阐述,为扩大蛋白多肽乳液在递送生物活性物质中的应用提供理论依据。

双蛋白纳米颗粒Pickering乳液的构建及稳定性研究

为获得稳定性较好的蛋白基Pickering乳液,实验采用pH循环法以绿豆蛋白和乳清蛋白为原料制备双蛋白纳米颗粒并进行表征,进一步以此为基质制备Pickering乳液,并对Pickering乳液微观结构、粒径及流变学等进行表征,同时探讨了乳液的加工稳定性。结果表明,获得了粒径为100~250 nm的蛋白纳米颗粒;其制备的Pickering乳液为水包油型,且具有良好稳定性;与单一蛋白纳米颗粒乳液比较,双蛋白纳米颗粒乳液的乳化特性及其本身的稳定性有所提高。乳液的流变学说明乳液出现了剪切稀化现象,形成了凝胶网络结构。随着双蛋白中乳清蛋白比例的增加,乳液粒径减小,稳定性增加。因此,双蛋白制备的纳米颗粒Pickering乳液理化性质得到改善。研究结果可为混合蛋白构建稳定的乳液体系及活性成分的递送提供参考。

核桃蛋白-低聚半乳糖复合纳米颗粒的制备及其Pickering乳液性质

以核桃蛋白(WalPI)和低聚半乳糖(GOS)为原料,采用pH循环-超声联合制备了WalPI-GOS,将其与茶油混合,制备了Pickering乳液。通过FTIR、纳米粒度及Zeta电位仪、紫外-可见分光光度计、荧光分光光度计、DSC对WalPI-GOS进行了表征,考察了m(WalPI)∶m(GOS)对WalPI-GOS颗粒特性及Pickering乳液性质的影响。结果表明,当m(WalPI)∶m(GOS)=10∶4时,WalPI-GOS和Pickering乳液具有最佳的性能。WalPI-GOS的平均粒径为82.08 nm,Zeta电位为–52.37 mV,乳化活性、乳化稳定性为31.12 m^(2)/g和4346.35 min;WalPI部分疏水基团被包埋于WalPI-GOS分子内部,降低了表面疏水性(840.81 a.u.),提高了游离巯基含量(8.78μmol/g)和熔融温度(93.74℃);WalPI与GOS的复合改变了WalPI的二级和三级结构,形成以β-折叠为主的二级结构,WalPI与GOS通过氢键、静电相互作用和疏水相互作用形成紧密的网络结构;Pickering乳液平均粒径仅为5.24μm,液滴均匀分布,形成了弹性凝胶网络结构;当剪切速率为0.1 s^(–1)时,具有最高的表观黏度(1.06 Pa·s)。WalPI与GOS间的高交联密度增强了Pickering乳液的凝胶网络结构。

藜麦蛋白Pickering乳液替代脂肪对牛肉丸冻融稳定性的影响

肉制品在冷冻储藏期间,其品质会受到一定影响,冻融循环会导致其持水力、pH值、色泽、质构等受到负面影响。基于藜麦蛋白Pickering乳液良好的冻融稳定性,该试验用藜麦蛋白Pickering乳液替代25%~100%的猪背膘,探究其在冻融循环过程中对牛肉丸品质的影响。结果表明,3次冻融循环后,对照组牛肉丸的持水力由85.70%降至80.42%,而用藜麦蛋白Pickering乳液替代脂肪后的持水力维持在85.32%~88.85%,其中乳液替代比例50%的稳定效果较好,此时解冻汁液流失率达到最低,为1.94%。同时,用藜麦蛋白Pickering乳液替代脂肪可以延缓牛肉丸冻融过程中pH值的降低以及色泽、硬度和咀嚼度的变化;冻融过程中,牛肉丸中的不易流动水逐渐向游离水转变,而以藜麦蛋白Pickering乳液替代脂肪可以抑制其转化程度。

乳清浓缩蛋白对松仁蛋白溶解度及其乳液稳定性的影响

为研究蛋白质-蛋白质相互作用对松仁蛋白(PKP)溶解度、结构和乳液性质的影响,以PKP和乳清浓缩蛋白(WPC)为研究对象,采用pH循环法制备PK P-WPC复合蛋白,利用SD S-PAGE、内源性荧光光谱、紫外-可见光谱、圆二色谱、荧光探针和ζ-电位等方法分析了复合蛋白结构特性和表面特性,再以PK P-WPC复合蛋白为原料,分别制备了油相体积分数为3%、10%和50%的乳液,并对制备的乳液性质进行了检测。结果表明:当WPC与PKP的质量比为1.0∶1.0,且体系pH值经历由7.0到12.0再回到7.0时的1次pH循环后,PKP的水溶性可从48.53%提高到92.43%。SD S-PAGE结果显示,PK P-WPC复合蛋白完整保留了PKP和WPC的亚基。内源性荧光光谱、紫外-可见光谱和圆二色谱结果表明,静电相互作用、疏水相互作用和氢键是驱动PKP和WPC相互作用的主要作用力,PKP与WPC相互作用使复合蛋白具有较高的结构韧性,抵抗酸诱导的构象折叠;WPC的加入改变了PKP的二级结构,α-螺旋、β-转角和无规卷曲结构的含量增加,而β-折叠结构相对含量降低。PK P-WPC复合蛋白具有较高的表面电荷(-34.74 mV)来抵抗蛋白质的聚集。与由PKP制备的乳液相比,由PK P-WPC制备的乳液平均粒径和乳层析指数减小,ζ-电位绝对值增大,稳定性显著提高。乳液的性质因油相体积分数的不同而有较大的差异。油相体积分数为3%的复合乳液液滴小且分布均匀,稳定性好于油相体积分数为10%和50%的复合乳液。通过pH循环法,通过添加WPC,提高了PKP的溶解度,获得了稳定性较佳的PKP乳液,研究可为新型蛋白产品的研发提供理论基础,拓宽松仁蛋白在加工食品中的应用范围,推动PK P-WPC双蛋白乳液研究的发展。