乳基蛋白类产品功能性质的比较研究

通过比较了乳蛋白浓缩物与酪蛋白、乳清分离蛋白在溶解性、持水性、乳化性、起泡性和凝胶性等功能性质上的区别.结果表明:乳蛋白浓缩物在持水性上表现最佳,比酪蛋白和乳清蛋白分别高61.04％和429.05％;溶解性比酪蛋白高19.38％,但比WPI低36.64％.在乳化性及乳化稳定性、起泡性及泡沫稳定性方面总体表现比酪蛋白好;乳蛋白浓缩物还可以形成凝胶,但没有乳清分离蛋白的凝胶性好.总之,乳蛋白浓缩物的总体性能要优于酪蛋白.     

热处理和调节pH改性乳清蛋白浓缩物对搅打稀奶油加工性质的影响

通过热处理和调节p H对乳清蛋白浓缩物80(Whey protein concentrate,WPC80)进行改性处理,并将改性后的WPC80添加至低脂稀奶油中,以改善其搅打性质。结果表明调节WPC80溶液的p H为3,在80℃下加热15min时具有最佳的溶解性和起泡性,相同p H条件下,不同的热处理时间会对溶解性和起泡性产生不同的影响;将热处理和p H改性后WPC80加入搅打稀奶油中,研究发现不同热处理时间,p H为5改性的WPC80可以显著提高搅打稀奶油的打发率(p<0.05),但是p H为7处理的WPC80使稀奶油的泡沫稳定性增加了154.67%~193.42%。因此可通过热处理和调节p H改性的WPC80来提高低脂稀奶油的搅打特性,且此操作方法简单易行。      

热处理和调节pH改性乳清蛋白浓缩物对搅打稀奶油加工性质的影响

通过热处理和调节p H对乳清蛋白浓缩物80(Whey protein concentrate,WPC80)进行改性处理,并将改性后的WPC80添加至低脂稀奶油中,以改善其搅打性质。结果表明调节WPC80溶液的p H为3,在80℃下加热15min时具有最佳的溶解性和起泡性,相同p H条件下,不同的热处理时间会对溶解性和起泡性产生不同的影响;将热处理和p H改性后WPC80加入搅打稀奶油中,研究发现不同热处理时间,p H为5改性的WPC80可以显著提高搅打稀奶油的打发率(p0.05),但是p H为7处理的WPC80使稀奶油的泡沫稳定性增加了154.67%~193.42%。因此可通过热处理和调节p H改性的WPC80来提高低脂稀奶油的搅打特性,且此操作方法简单易行。     

纳米粉碎对乳清浓缩蛋白及其微凝胶颗粒结构和界面性质的影响

该文研究纳米粉碎对乳清浓缩蛋白（whey protein concentrate,WPC）及乳清浓缩蛋白微凝胶颗粒（whey protein concentrate micro-gel particles,WPM）粒径、分子量、游离巯基含量和内源性荧光光谱的影响,探究蛋白质多尺度结构的变化对WPM稳定乳液的微流变特性、贮藏稳定性和微观形貌的影响,以表征乳清浓缩蛋白界面性质的变化规律。研究结果表明：纳米粉碎预处理可以显著降低乳清浓缩蛋白的粒径并增强粒径分布的集中程度。纳米粉碎预处理后,蛋白质分子量并无明显差异,但是游离巯基含量明显减少,证明了大量分子内二硫键的形成;内源性荧光光谱结果显示WPC的最大吸收波长由333 nm红移至339 nm处,说明内埋的疏水性基团暴露,表面疏水性增强。经纳米粉碎和微粒化处理后,sWPM-8h乳液具有最强的黏性和弹性、较小的固液平衡值、最小的流动性指数和最高的贮藏稳定性。综上,纳米粉碎可以改善乳清浓缩蛋白的界面性质。     

大米乳清蛋白的研究

采用相应的国标法对大米乳清蛋白的基本组成成分进行测定,SDS-PAGE凝胶电泳对其分子质量进行测定,并对其溶解性、乳化性、发泡性、持水持油性等功能性质及氨基酸组成进行了研究。结果表明,大米乳清蛋白中蛋白质质量分数达83.09%;分子质量分布在1.8、22、35、60、80 ku。与大豆分离蛋白比较,大米乳清蛋白的溶解性、乳化性相近,乳化稳定性、发泡性与发泡稳定性、持油性较好,持水性较差。大米乳清蛋白中,赖氨酸质量分数高达14.51%,是一种必需氨基酸含量均衡的植物蛋白。     

淀粉-乳清蛋白复合条件对体系润滑特性的影响

探索浓缩乳清蛋白（whey protein concentrate,WPC）是否参与淀粉糊化过程及复合质量分数对淀粉-WPC复合体系润滑特性的影响,选取聚二甲基硅氧烷作为摩擦副,模拟口腔加工条件对淀粉-WPC复合体系的润滑特性进行研究。结果显示：在口腔加工的0～60 s时间范围,WPC参与和未参与淀粉糊化,2种复合方式得到复合体系的润滑性能存在显著差异（P<0.05）,且在不同植物源淀粉间存在显著差异（P<0.05）;在WPC复合质量分数1%～7%范围内,WPC的复合显著提升了原淀粉凝胶体系的润滑特性,且WPC质量分数对复合体系润滑特性提升呈非线性关系具有正显著影响（P<0.05）。该研究为提升淀粉蛋白质基质食品的质地口感提供理论参考。     

乳清浓缩蛋白与卵清蛋白复合膜的制备及其性能

本文以乳清蛋白（Whey protein concentrate,WPC）和卵清蛋白（Egg white protein,EWP）为成膜基质,添加5 U/g_蛋白转谷氨酰胺酶（Transglutaminase,TG）制备WPC/EWP复合膜,分别研究WPC和EWP质量比、膜液pH、甘油添加量对WPC/EWP复合膜结构及性能的影响。结果表明,当WPC/EWP质量比为1:3,成膜液pH为8,甘油添加量为35%时,电镜结果表明形成的复合膜结构致密无孔隙,红外结果显示WPC和EWP有较好的相容性。WPC/EWP复合膜的水蒸气透过率为2.08×10?10 g·s?1m?1Pa?1,透光率为73.90%,抗拉强度为1.60 MPa,断裂伸长率为151.96%。WPC、EWP和甘油在膜液pH为8时具有良好的融合性,能显著（P<0.05）提高WPC/EWP复合膜的机械性能。     

超声处理对大豆分离蛋白-乳清分离蛋白混合蛋白功能特性的影响

为了研究超声处理对大豆分离蛋白（soy protein isolate,SPI）-乳清分离蛋白（whey protein isolate,WPI）混合体系乳化性、凝胶性以及结构状态的影响,采用不同超声功率处理混合蛋白体系,分析混合蛋白乳化活性、乳化稳定性、凝胶强度、持水性等功能特性变化,并采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳、紫外光谱、扫描电子显微镜研究其结构特征变化。结果表明：SPI-WPI混合体系在超声功率为300 W时乳化活性与乳化稳定性分别达到最大值（76.46 m2/g和22.83 min）;紫外光谱发生轻微红移,说明内部基团暴露,蛋白结构发生改变;SPI-WPI混合体系凝胶强度与持水性在超声功率300 W时均达到最大值,分别为1 000.93 g和87.11%,与扫描电子显微镜观察结果一致,混合蛋白凝胶具有致密、规则的三维网状结构。说明超声处理能有效提高SPI-WPI混合蛋白的功能特性。     

蛋白组分对米蛋白功能性质影响的研究

以不同配比米蛋白组分的样品为试材,比较各样品的功能性质变化,明确各蛋白组分对蛋白产品品质影响的差异,为今后进行分子设计和重组生产米蛋白产品提供理论支撑。通过各蛋白样品的溶解性,乳化特性,起泡特性,持水性/持油性等功能性质研究,结果表明,米糠浓缩蛋白的溶解性比大米浓缩蛋白高200%左右;米糠蛋白各功能性质显著优于大米蛋白,但大米蛋白的起泡稳定性比米糠蛋白提高近20%。米蛋白中的清蛋白提高产品的溶解性、持水性/持油性,降低起泡稳定性;醇溶蛋白提高产品的乳化特性;谷蛋白提高产品的起泡稳定性。蛋白产品的功能性质与蛋白组分的组成密切相关。     

大豆乳清蛋白功能特性的研究

对经过膜分离技术提取的大豆乳清蛋白的功能特性进行研究。主要研究了pH对大豆乳清蛋白的溶解特性、起泡性能及乳化性能的影响,并对大豆乳清蛋白的组成成分进行了电泳分析。结果表明,大豆乳清蛋白具有较好的溶解性及起泡性,但泡沫稳定性及乳化性不如大豆分离蛋白。大豆乳清蛋白主要包含6种成分。     

Production of a high gel strength whey protein concentrate from cheese whey

In order to develop a process for the production of a whey protein concentrate (WPC) with high gel strength and water-holding capacity from cheese whey, we analyzed 10 commercially available WPC with different functional properties. Protein composition and modification were analyzed using electrophoresis, HPLC, and mass spectrometry. The analyses of the WPC revealed that the factors closely associated with gel strength and water-holding capacity were solubility and composition of the protein and the ionic environment. To maintain whey protein solubility, it is necessary to minimize heat exposure of the whey during pretreatment and processing. The presence of the caseinomacropeptide (CMP) in the WPC was found to be detrimental to gel strength and water-holding capacity. All of the commercial WPC that produced high-strength gels exhibited ionic compositions that were consistent with acidic processing to remove divalent cations with subsequent neutralization with sodium hydroxide. We have shown that ultrafiltration/diafiltration of cheese whey, adjusted to pH 2.5, through a membrane with a nominal molecular weight cut-off of 30,000 at 15 degrees C substantially reduced the level of CMP, lactose, and minerals in the whey with retention of the whey proteins. The resulting WPC formed from this process was suitable for the inclusion of sodium polyphosphate to produce superior functional properties in terms of gelation and water-holding capacity.     

Foaming and Emulsifying Properties of Whey Protein Concentrates As Affected by Lipid Composition

Freeze-dried WPC, containing 35 and 75% protein were manufactured by pretreating whey with calcium chloride and heat. These and commercial WPC were subjected to proximate analysis and lipid classes, phospholipid classes, free fatty acids (FFA), and monoacylglycerols (MAG) composition were determined. Solubility, thermal, foaming, and emulsifying properties of the WPC were studied. Pretreatment increased calcium and phosphorus contents and decreased the contents of all other minerals. The pretreatment had no effect on solubility, denaturation enthalpy, and onset temperature of denaturation of WPC. These values were comparable to those of commercial WPC. Foaming capacity and emulsion stability were unaffected, but foam stability increased and emulsifying capacity decreased due to pretreatment. Overall, total lipids and lipid class contents of experimental WPC were too low to affect surface properties of WPC.     

Foaming Properties of Lipid-Reduced and Calcium-Reduced Whey Protein Concentrates

The ability of whey protein concentrates (WPC) to form highly expanded and stable foams is critical for food applications such as whipped toppings and meringue-type products. The foaming properties were studied on six experimental and three commercial WPC, manufactured by membrane fractionation processes to contain reduced lipids and calcium. Lipid-reduced WPC had excellent foaming properties. Experimental delipidized WPC MF 0.45 and commercial delipidized WPC E had higher (P < 0.05) foam expansion than egg white protein (EWP). However. WPC B made bv low-pH UF and isoelectric orecinitation did not form a foam. Lipids and ash were the main factors affecting foaming properties.     

Relationship between functional properties and aggregation changes of whey protein induced by high pressure microfluidization

Aggregation changes of whey protein induced by high-pressure microfluidization (HPM) treatment have been investigated in relation with their functional properties. Whey protein was treated with HPM under pressure from 40 to 160 MPa. Functional properties (solubility, foaming, and emulsifying properties) of whey protein concentrate (WPC) ultrafiltered from fluid whey were evaluated. The results showed significant modifications in the solubility (30% to 59%) and foaming properties (20% to 65%) of WPC with increasing pressure. However, emulsifying property of WPC treated at different pressures was significantly worse than untreated sample. To better understand the mechanism of the modification by HPM, the HPM-induced aggregation changes were examined using particle size distribution, scanning electron microscopy, and hydrophobicity. It was indicated that HPM induced 2 kinds of aggregation changes on WPC: deaggregation and reaggregation of WPC, which resulted in the changes of functional properties of WPC modified by HPM.     

The Potential Source of B. licheniformis Contamination During Whey Protein Concentrate 80 Manufacture

The objective of this study was to determine the possible source of predominant Bacillus licheniformis contamination in a whey protein concentrate (WPC) 80 manufacturing plant. Traditionally, microbial contaminants of WPC were believed to grow on the membrane surfaces of the ultrafiltration plant as this represents the largest surface area in the plant. Changes from hot to cold ultrafiltration have reduced the growth potential for bacteria on the membrane surfaces. Our recent studies of WPCs have shown the predominant microflora B. licheniformis would not grow in the membrane plant because of the low temperature (10 °C) and must be growing elsewhere. Contamination of dairy products is mostly due to bacteria being released from biofilm in the processing plant rather from the farm itself. Three different reconstituted WPC media at 1%, 5%, and 20% were used for biofilm growth and our results showed that B. licheniformis formed the best biofilm at 1% (low solids). Further investigations were done using 3 different media; tryptic soy broth, 1% reconstituted WPC80, and 1% reconstituted WPC80 enriched with lactose and minerals to examine biofilm growth of B. licheniformis on stainless steel. Thirty‐three B. licheniformis isolates varied in their ability to form biofilm on stainless steel with stronger biofilm in the presence of minerals. The source of biofilms of thermo‐resistant bacteria such as B. licheniformis is believed to be before the ultrafiltration zone represented by the 1% WPC with lactose and minerals where the whey protein concentration is about 0.6%.     

pH值碱性偏移结合热处理对米糠蛋白结构和功能性质的影响

研究pH值碱性偏移（pH 11）结合热处理（50、60 ℃）对米糠蛋白结构和功能性质的影响。结果表明,pH值碱性偏移促使米糠蛋白二级结构由有序向无序转化,pH值碱性偏移结合热处理使得米糠蛋白二级结构呈现折叠-去折叠-复折叠的复杂变化,并伴随巯基氧化。pH值碱性偏移促使米糠蛋白展开,随着处理时间的延长,米糠蛋白重新聚集,热处理会加剧聚集程度。pH值碱性偏移使得米糠蛋白持水性、起泡性、泡沫稳定性、乳化性和乳化稳定性显著下降,仅持油性显著改善;随着处理时间的延长,米糠蛋白持水性、起泡性、乳化性和乳化稳定性逐渐上升,其中乳化性上升幅度最大。pH值碱性偏移结合热处理可显著改善米糠蛋白的持水性、起泡性、泡沫稳定性和乳化稳定性,同时也会降低米糠蛋白的持油性和乳化性。     

Gelation Properties of Lipid-Reduced, and Calcium-Reduced Whey Protein Concentrates

Gels made from six experimental whey protein concentrate (WPC) processes using chemical pretreatment, ultrafiltration and microfiltration (MF) of Swiss cheese whey, and three commercial WPC, were compared for rheological, microstructural and sensory properties. Based on relations between shear stress (ST) and total sulfhydryl levels, we contirmed that disulfide bonding is important in gelation. Other components, i.e., lipids, lactose, calcium and sodium, interacting simultaneously, affected gel formation. Gel water holding capacity (WHC) was related to microstructure but not to ST. WHC was useful to characterize the 3-dimensional gel structure formations. Light microscopy showed the strongest gel had a fine-stranded, solvent-retaining structure.     

High hydrostatic pressure modification of whey protein concentrate for use in low-fat whipping cream improves foaming properties

Whey is the inevitable by-product of cheese production. Whey can be incorporated into a variety of foods, but little has been done to investigate its suitability in whipping cream. The objective of this work was to evaluate the foaming properties of selected low-fat whipping cream formulations containing whey protein concentrate (WPC) that did or did not undergo high hydrostatic pressure (HHP) treatment. Fresh whey was concentrated by ultrafiltration, pasteurized, and standardized to 8.23% total solids and treated with HHP at 300 MPa for 15 min. Viscosity, overrun, and foam stability were determined to assess foaming properties. Sensory evaluation was conducted with 57 panelists using a duo-trio difference test. The optimal whipping time for the selected formulations was 3 min. Whipping cream containing untreated WPC and HHP-treated WPC resulted in greater overrun and foam stability than the control whipping cream without WPC. Panelists distinguished a difference between whipping cream containing untreated WPC and whipping cream containing HHP-treated WPC. High hydrostatic pressure-treated WPC can improve the foaming properties of low-fat whipping cream, which may justify expansion of the use of whey in whipping cream and application of HHP technology in the dairy industry.     

储藏温度对大米蛋白功能特性的影响

为了探究储藏温度对不同大米蛋白功能特性的影响,本实验以中国东北地区‘稻花香二号’‘辽星’和‘盐丰’大米为对象,以大米蛋白的溶解性、持水性、持油性、起泡性质和乳化性质为指标,分析其在4、30 ℃和70 ℃储藏期间的变化情况,以期为优质大米储藏过程中蛋白品质控制提供参考。结果表明,蛋白持水性和起泡性在不同储藏温度下随时间延长总体呈下降趋势,而持油性总体呈上升趋势。‘稻花香二号’和‘辽星’蛋白的泡沫稳定性在不同储藏温度下随时间延长总体呈上升趋势,而‘盐丰’蛋白总体呈下降趋势。在4 ℃储藏期间,3 种大米蛋白的乳化稳定性总体呈下降趋势,‘稻花香二号’和‘辽星’的蛋白溶解度和乳化性总体呈下降趋势,而‘盐丰’的蛋白溶解度和乳化性呈显著上升趋势（P＜0.05）。在30 ℃储藏期间,3 种大米蛋白溶解度总体呈下降趋势,而乳化性和乳化稳定性总体显著上升（P＜0.05）。在70 ℃储藏期间,3 种大米蛋白的溶解度和‘辽星’蛋白的乳化稳定性总体显著下降（P＜0.05）,而‘稻花香二号’蛋白乳化性总体呈上升趋势。综上,在不同温度储藏期间,3 种大米蛋白的功能特性均发生显著变化。     

Impact of whey protein isolates and concentrates on the formation of protein nanoparticles‐stabilised Pickering emulsions

Whey protein nanoparticles (NPs) were prepared by heat‐induced method. The influences of whey protein isolates (WPIs) and concentrates (WPCs) on the formation of NPs were first investigated. Then Pickering emulsions were produced by protein NPs and their properties were evaluated. After heat treatment, WPC NPs showed larger particle size, higher stability against NaCl, lower negative charge and contact angle between air and water. Dispersions of WPC NPs appeared as higher turbidity and viscosity than those of WPI NPs. The interfacial tension of WPC NPs (~7.9 mN/m at 3 wt% NPs) was greatly lower than that of WPI NPs (~12.1 mN/m at 3 wt% NPs). WPC NPs‐stabilised emulsions had smaller particle size and were more homogeneous than WPI NPs‐stabilised emulsions. WPC NPs‐stabilised emulsions had higher stability against NaCl, pH and coalescence during storage.