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.     

Comparison of functional properties of 34% and 80% whey protein and milk serum protein concentrates

This study compared the functional properties of serum protein concentrate (SPC) with whey protein concentrate (WPC) made from the same milk and with commercial WPC. The experimental SPC and WPC were produced at 34% or 80% protein from the same lot of milk. Protein contents of WPC and SPC were comparable; however, fat content was much lower in SPC compared with WPC and commercial WPC. The effect of drying methods (freeze vs. spray drying) was studied for 34% WPC and SPC. Few differences due to drying method were found in turbidity and gelation; however, drying method made a large difference in foam formation for WPC but not SPC. Between pH 3 and 7, SPC was found to have lower turbidity than WPC; however, protein solubility was similar between SPC and WPC. Foaming and gelation properties of SPC were better than those of WPC. Differences in functional properties may be explained by differences in composition and extent of denaturation or aggregation.     

蛋白含量对牦牛乳清蛋白浓缩物功能特性的影响

通过不同截留分子质量的再生纤维素膜过滤纯化牦牛原乳清液和牦牛甜乳清液,分别制取牦牛原乳清蛋白浓缩物(native whey protein concentrate,NWPC)和牦牛甜乳清蛋白浓缩物(sweet whey protein concentrate,SWPC),研究蛋白含量不同的乳清蛋白浓缩物(whey pr...     

Factors Affecting the Functional Properties of Whey Protein Products: A Review

Numerous why protein products (WPP) have been developed as excellent food ingredients with unique functional properties. However, the functional properties of WPP are affected by several compositional and processing factors. Recently, novel processing technologies such as high hydrostatic pressure, ultrasound, extrusion and tribomechanical activation have been used to modify the functional properties of WPP. Also, WPP have been used as delivery systems for functional ingredients and in edible films. The present paper reviews the latest developments in the role of different factors on the functional properties of WPP with emphasis on novel processing technologies, and interaction with other food ingredients     

A comparison of drying operations on the rheological properties of whey protein thickening ingredients

An existing procedure for the alteration of whey proteins into a cold‐set thickening agent was modified by developing a spray‐drying operation to replace the prohibitively expensive freeze‐drying step. The original and the modified derivatization procedures were used with a commercial whey protein concentrate (WPC). The freeze‐dried and spray‐dried derivatized WPC powders, along with polysaccharide thickeners, were reconstituted in water and evaluated by using a range of rheological studies. The effects of temperature, concentration, and shear on viscosity as well as the mechanical spectra were assessed to characterize the ability of the powders to function in food systems. Rheological characterization revealed the modified derivatization procedure yielded an ingredient having the same cold‐set thickening and gelling ability as the original derivatized powder. The modified whey proteins were also able to achieve, at higher usage levels, textural properties similar to several polysaccharide thickeners. Use of a spray‐drying technique created a more economical process for the production of a whey protein ingredient that was suitable for contributing viscosity and texture to a wide range of food systems.     

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。     

Viscous Sol and Gel Formation from Process Whey Protein Below 25°C

The viscosity of process whey protein (PWP; whey protein preheated under salt-free conditions) solution increased and led to gel formation with incubation at ambient or lower temperature by NaCl addition. Viscosity of PWP solution (70 mg/mL, 38.3 sec^-1, 40 min incubation) either with NaCl up to 120 mM or without NaCl decreased with increasing temperature, viscosity gave straight lines in an Andrade plot below 25°C, whereas viscosity of PWP solution with NaCl sharply increased with increase in temperature above 25°C. This suggested that association of the aggregates of PWP molecules occurred above 25°C by addition of NaCl, and that network formation by such aggregates might cause gelation.     

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.     

Process development for a novel milk protein concentrate with whey proteins as fibrils

Milk protein concentrate (MPC) is a preferred ingredient to provide nutritional and functional benefits in various dairy and food products. Altering the protein configuration and protein-protein interactions in MPC can provide a novel functionality and may open doors for new applications. The fibrilization process converts the globular structure of whey proteins to fibrils and consequently increases viscosity and water holding capacity compared with the native protein structure. The objective of the current work was to selectively convert the whey proteins in MPC as fibrils. For this purpose, simulated control model MPC was prepared by combining solutions of micellar casein concentrate (MCC) and milk whey protein isolate (mWPI) to give casein and whey protein in an 80:20 ratio. The mWPI solution was converted to fibrils by heating at low pH, neutralized, and combined with MCC solution similar to control model MPC and termed “fibrillated model MPC.” Thioflavin T fluorescence value, transmission electron microscopy, and gel electrophoresis confirmed the fibril formation and their survival after neutralization and mixing with MCC. Further, the fibrillated mWPI showed significantly higher viscosity and consistency coefficient than nonfibrillated mWPI. Similarly, fibrillated model MPC showed significantly higher viscosity and consistency coefficient compared with control model MPC. Hence, the fibrillated model MPC can be used as ingredient to increase viscosity. Heat coagulation time was found to be significantly higher for control model MPC compared with fibrillated model MPC.     

Assessment of the techno-functionality,starch digestion rates and protein quality of rice flour–whey protein instant powders produced in a twin extruder

Whey protein concentrate (WPC) is an important raw material for the production of instant beverages due to its protein properties. A central composite design was devised to analyse the effects of thermoplastic extrusion of 2:1 rice flour:WPC blends in physical, chemical–nutritional and functional properties. Three main factors were selected, screw speed (225–375 r.p.m.), conditioning moisture (17%–23%) and temperature (120–180 °C) to evaluate effects on water absorption (WAI) and solubility (WSI) indexes, viscoamylograph cold and final viscosities, in vitro protein and starch digestibilities and starch hydrolysis indexes (HI). A second-order model showed that linear parameters were significant for all variables studies. Conditioning moisture affected properties more significantly than temperature and screws speed. The best treatment (16% moisture conditioning, 180 °C last barrel zone and screws rotating at 350 r.p.m.) in terms of water solubility had high starch in vitro digestibility and excellent protein quality determined in vitro and in vivo with weanling rats.     

Interactive Effects of Factors Affecting Gelation of Whey Proteins

The individual effects of heating time (15–120 min), pH (3–9) and NaCl (0–2M), sucrose (0–30% w/v) and protein (10–30% w/v) concentrations on the strength, turbidity and water holding capacity were investigated on a commercial whey protein concentrate (WPC, 75% protein) when heated at temperatures ranging from 65 to 90°C. Interactive effects were investigated using a four-variable, five-level central composite rotatable design (CCRD) analyzed by response surface methodology (RSM). Gel strength (GS) and water holding capacity (WHC) increased with protein concentration, heating temperature and time. Increasing sucrose concentration decreased GS but increased WHC. Increasing NaCl concentration increased GS and WHC below pH 5 but resulted in weaker gels at high pH (>7).     

乳清蛋白改性综述

通过改性可以加强乳清蛋白的功能性质，从而扩大它在食品中的应用。乳清蛋白可以通过化学法、酶法和物理法得以改性。化学法包括酰化、酰胺化、酯化、磷酸化、硫醇化、还原烷基化和共价连接氨基酸等；酶法改性主要为部分水解，蛋白质分子内或分间交联和连接特殊功能基团；物理改性有热变性、与生物大分子聚合以及质构化。     

Hydrophilic and Rheological Properties of Brewer's Yeast Protein Concentrates

Protein solubility (PS), water-holding capacity (WHC), viscosity and gelling properties were studied in brewer's yeast protein concentrates prepared by 3 procedures: isoeletric precipitation of protein (I-PC), extraction with 0.5M NaClO₄(P-PC) or with 3% sodium trimetaphosphate (TMP-PC). PS was higher for TMP-PC and lower for P-PC at pH 4 to 12. WHC increased with increasing pH in all concentrates, but was higher for TMP-PC. The presence of NaCl (0.1 M and 1.0M) reduced to 50% the WHC of TMP-PC. Gelling properties of a 10% protein dispersion were studied in the TMP-PC preparation. Hardness and fracturability of the gel (TA-XT2 texturometer) was 35 and 31 gf, respectively. Apparent viscosity of a 3% dispersion at pH 7.0 was lower for I-PC and higher but similar for TMP-PC and P-PC. All concentrates showed pseudoplastic rheological behavior.     

乳清浓缩蛋白可食用包装膜的研制

以乳清浓缩蛋白为基质,通过加入成膜剂、增塑剂制得可食用包装膜。研究了不同成膜剂添加量、不同增塑剂添加量、不同转谷氨酰胺酶添加量对成膜的影响。通过响应面分析表明,制备乳清浓缩蛋白可食用膜的最佳条件是：乳清浓缩蛋白浓度10%、添加山梨醇5%、无水氯化钙1.2166%、转谷氨酰胺酶0.018%,在60~65℃的温度范围成膜。     

Rheological properties of commercial whey protein samples from the MADGELAS survey

Summary Thermally induced gelation of commercial whey protein samples from the Molecular Basis of the Aggregation, Denaturation, Gelation and Surface Activity of Whey Proteins ( MADGELAS ) survey has been studied in order to develop a current status report on their rheological properties. Solutions of 10% protein (w/v) were prepared in distilled water, 200 mm NaCl or 10 mm CaCl₂ at neutral pH. Small-scale deformation of the samples was measured by dynamic oscillatory rheometry using a Bohlin CS Rheometer. Large-scale deformation at penetration mode was measured using a Texture Analyser (Stable Micro Systems, Surrey, UK). For solutions containing salts, there was a general trend for gel point to decrease and G' values to increase, the effect being more marked in the presence of NaCl. Similarly, force values at failure also tended to increase in the presence of salts. Results obtained with samples of similar protein composition dissolved in water were highly scattered, these differences being reduced in the presence of added salts.     

乳清蛋白-大米淀粉混合体系动态流变学特性研究

乳清蛋白和淀粉因其较好的凝胶形成特性而被广泛用于食品配料。通过动态流变仪研究乳清蛋白-大米淀粉混合体系的动态流变性,并同时考虑了离子及离子强度对流变特性的影响。结果表明,在淀粉比例低于50%时,乳清蛋白-大米淀粉混合体系升温过程的储能模量(G')和损耗模量(G\")明显低于乳清蛋白,而当淀粉比例升至50%时,最终的G'和G\"已经远远超过乳清蛋白;此外,降温过程中混合体系的最终G'和G\"也远高于乳清蛋白,表明蛋白质淀粉分子间的相互作用的增强对混合凝胶的特性有一定的协效性,强化了形成的凝胶网络。随着盐离子浓度的提高,混合体系的G'和G\"均持续降低,表明盐离子和蛋白质分子间的相互作用一定程度上阻碍了淀粉与蛋白质分子间的相互作用,弱化了形成的凝胶网络。     

乳清蛋白功能活性的研究

乳清蛋白是牛乳乳清中存在的一类蛋白质,其必需氨基酸种类齐全、数量充足且比例适当,是一种营养价值较高的优质蛋白,在维持机体肠道、肌肉组织的健康和补充体内的谷胱甘肽数量、抗氧化等方面有重要作用。乳清蛋白中还含有β-乳球蛋白、α-乳白蛋白、血清白蛋白、免疫球蛋白、乳铁传递蛋白以及乳过氧物酶等多种生物活性蛋白。这些物质参与构成机体非特异性防御屏障,在抗菌、抗病毒、免疫调节等方面也发挥积极作用。