Structure and functional properties of rice protein–dextran conjugates prepared by the Maillard reaction

Dextran was grafted on to rice protein (RP) by the wet‐heating Maillard reaction, and the structure and functional properties of the rice protein–dextran conjugates (RPDCs) were investigated. The RPDCs obtained by the Maillard reaction exhibited superior functionality compared with original RP. The solubility, emulsifying activity index, emulsifying stability index, foaming activity index and foaming stability of the RPDCs increased by factors of 7.50, 1.79, 2.20, 1.69 and 2.01, respectively, compared to original RP. The molecular weight, particle size distribution, surface hydrophobicity, secondary structures, amino acid compositions and chemical bonds of RPDCs were also characterised. The structure–function relationship was preliminary discussed, and the relationship suggests that the improvements in the functional properties were closely related to structural changes.     

Functionality of Milk Powders and Milk‐Based Powders for End Use Applications—A Review

Abstract: Newer variants of milk powders and milk‐based powders are being produced are looking for prospective end users. Powders possess physical and functional properties that are of significance in its usage notably powder structure, particle size distribution, powder density, bulk density, particle density, occluded air, interstitial air, flowability, rehydration (wettability, sinkability, dispersibility, solubility), hygroscopicity, heat stability, emulsifying ability, water activity, stickiness, caking, and others. Some of the functional properties of significance to milk powders and milk‐based powders are discussed in this review. Applications with regard to specific milk powders for reconstituted cheese making, coffee creamers, and those suited for milk chocolate and for the baking industry are described.     

Invited review: spray-dried dairy and dairy-like emulsions--compositional considerations

Milk constituents [caseins, whey proteins (WP), lactose, and anhydrous milk fat] are used widely in the manufacture of dehydrated dairy and dairy-like emulsions. When sodium caseinate- (NaCas) and WP-stabilized emulsions with an oil-to-protein ratio ranging from 0.25 to 5 are dehydrated, NaCas is a more effective encapsulant than WP because of its superior emulsifying properties and resistance to heat denaturation. Denaturation degree of WP during drying has been associated with increased powder surface fat and larger droplet size after reconstitution. Encapsulation of NaCas-stabilized emulsions improves in the presence of lactose; powder surface fat was reduced from 30 to <5% when lactose was added at a 1:1 ratio to NaCas in an emulsion containing 30% (wt/wt) oil. This has been related to the ability of lactose to form solid-like (or glassy) capsules during sudden dehydration. Encapsulation of WP-stabilized emulsions is not improved by addition of lactose, although there are conflicting reports in the literature. Storage stability of dehydrated dairy-like emulsions is strongly linked to lactose crystallization as release of encapsulated material occurs during storage at high relative humidities (e.g., 75%). The use of alternative carbohydrates as “matrix-forming” materials (such as maltodextrins or gum arabic) improves storage stability but compromises the emulsion droplet size after reconstitution. The composition of the powder surface has been recognized as a key parameter in dehydrated emulsion quality. It is the chemical composition of the powder surface that dictates the behavior of the bulk in terms of wettability, flowability, and stability. Analyses, using electron spectroscopy for chemical analysis of the surface of industrial milk powders and dehydrated emulsions that mimicked the composition of milk, showed that powder surface is covered mainly by fat, even when the fat content is very low (18 and 99% surface fat coverage for skim milk and whole milk powders, respectively). The functional properties of milk constituents during emulsion dehydration are far from being thoroughly understood; future research needs include a) the encapsulation properties of pure micellar casein; b) a deeper understanding of colloidal phenomena (such as changes in the oil-water and air-oil interfaces) that occur before, during, and after dehydration, which ultimately define emulsion stability after drying; and c) reconciliation of the current different views on powder surface composition.     

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。     

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 protein concentrate,WPC）主要成分（乳糖含量、pH值和总蛋白质含量）和功能特性（溶解性、持水性、持油性、起泡性、乳化性及热稳定性）的特征。结果表明：10 000 Da再生纤维素膜透析得到的牦牛WPC中总蛋白含量达到80%以上,不含乳糖,功能特性（溶解性、持水性、持油性、起泡性、乳化性及热稳定性）均显著高于经3 500 Da卷式膜、5 000 Da再生纤维素膜透析得牦牛WPC,WPC蛋白含量越高,其功能特性越好;不同蛋白含量的牦牛SWPC起泡能力、泡沫稳定性、乳化活性和乳化稳定性均显著（P＜0.05）高于牦牛NWPC。牦牛乳WPC最不稳定温度为85 ℃,高于荷斯坦牛乳WPC的80 ℃,热处理会适当改善牦牛WPC的起泡性能、乳化性能和热稳定性。通过膜牦牛处理获取的高蛋白含量的WPC,功能特性较好,应用广泛,对解决牦牛乳清资源的利用问题、保护环境、提高企业的经济效益起到关键性作用。     

Egg-shell like structure in dried milk powders

The development of an egg-shell like structure in skim milk powder has been investigated in a stirred fluidized-bed dryer at various temperatures and humidities. The developed particles have crystalline surfaces and amorphous cores. The SEM analysis shows a thin layer of lactose crystals (at the nano-scale) that is formed on the surface of the powder while the XRD analysis shows that the particle cores are still amorphous (egg-shell form), so the surface properties have improved while the bulk desirable properties (of good solubility) have been retained. The resulting powders show better flowability and stability and less cake formation during storage by retaining good rehydration and dissolution times. The nano-coating of milk powders by crystalline lactose from the powder itself and the improvement in stability and flowability could be a worthwhile solution for dairy industries.     

Functional Properties of Water-soluble Proteins from Silver Carp (Hypophthalmichthys molitrix) Conjugated with Five Different Kinds of Sugar

Water-soluble proteins (WSP) from silver carp denature easily during thermal processing, leading to the reduction of functional properties. In order to improve the functional properties of WSP and to utilize its resources efficiently, five different kinds of sugars (i.e., xylose, glucose, galactose, oligo-isomaltose, and dextran-10) were used to conjugate with WSP by Maillard reaction. Results suggested that the use of the Maillard reaction improved the solubility, heat stability, and emulsifying properties of WSP. With the increase of molecular weight (MW) of the sugars, the solubility, emulsifying properties, and total sulfhydryl (SH) groups of WSP increased, while the surface hydrophobicity decreased. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of the five Maillard reaction products (MRPs) showed that xylose reacted easily with WSP than did the other four kinds of sugar. Dextran-10 conjugated to WSP could efficiently improve the functional properties of WSP during heat processing.     

Effect of heating on Maillard reactions in milk

Heated milk is subject to the Maillard reaction; lactose and lysine residues in milk proteins (mainly casein) are the reactants. An overview is given of the early, advanced and final stages of the Maillard reaction as it occurs in milk. The early Maillard reaction is confined to the formation of the protein-bound Amadori product lactulosyllysine. Breakdown of the Amadori product leads to formation of all kinds of advanced Maillard reaction products such as lysylpyrraline, pentosidine, hydroxymethylfurfural, (iso)maltol, furfurals and formic acid. The content of these compounds in heated milk is, however, very low (with the exception of formic acid), and does not correspond to the breakdown of Amadori product in quantitative terms. The final stage, in which melanoidins (brown pigments) are formed and protein polymerization occurs, is largely unknown from a chemical point of view, let alone quantitatively. The conclusion can only be that not all important compounds are yet identified. Some experimental data for heated milk are given to illustrate the various stages of the Maillard reaction in heated milk. A kinetic analysis of the Maillard reaction is difficult because it is such a complicated reaction with many parallel and consecutive steps; in addition, one of the reactants, lactose, is also subject to another reaction, namely isomerization followed by degradation. The kinetics can be tackled by kinetic, multiresponse modelling, and this approach is illustrated. It appears that the temperature dependence of the (early) Maillard reaction is lower than for the simultaneously occurring isomerization reactions of lactose. The use of several components formed in the Maillard reaction to evaluate the heat intensity given to milk is discussed.     

Creating proteins with novel functionality via the Maillard reaction: a review

Proteins are widely utilized to add functional properties, such as gelling and emulsification to foods. These attributes depend on a number of factors such as molecular structure of the protein, the pH, and the composition of its chemical environment. There is substantial evidence to suggest that the functional properties of food proteins can be further improved by derivatization. Covalent bonding of proteins to polysaccharides and smaller reducing sugars via the Maillard reaction has been shown to alter the functionality of proteins without requiring the addition of chemical reagents. Establishment of a technologically feasible method for preparing the conjugates and optimization of the processing conditions, however, is needed to promote their development as functional food ingredients. This paper provides a state-of-the-art contribution to the impact of the Maillard reaction on protein functionality. It presents a deeper understanding of the influence of processing conditions and reactant formulation on improving desirable properties of proteins. In particular attention is given to how potential improvements could be achieved in the emulsifying, textural, and solubility properties of proteins to add value to commodity food ingredients. Elements that are considered to be critical to the design of functional Maillard conjugates are highlighted and suggestions proposed to facilitate progress in this area.     

糖对谷氨酰胺转氨酶交联米渣蛋白美拉德反应产物结构与功能的影响

将不同相对分子质量的核糖、葡萄糖、乳糖、阿拉伯胶与谷氨酰胺转氨酶(transglutaminase,TG)交联的米渣蛋白(rice dreg protein,RDP)进行美拉德反应,并分析美拉德反应产物(Maillard reaction products,MRPs)的结构、功能特性。结果表明:不同相对分子质量的糖与TG交联RDP在美拉德反应过程中,随着反应的进行,接枝度、褐变度及体系的p H值有明显变化,其中核糖和葡萄糖的变化最为明显,其次是乳糖、阿拉伯胶。结构上,核糖最易与TG交联RDP中赖氨酸和精氨酸自由氨基发生反应;功能性质上,MRPs的溶解性和乳化特性较原TG交联RDP都得到了不同程度的改善,从强到弱依次是核糖、葡萄糖、乳糖、阿拉伯胶。所有样品的流变学特性都表现出假塑性流体所特有的剪切变稀现象,葡萄糖和核糖的MRPs表观黏度较原TG交联RDP大,乳糖和阿拉伯胶的MRPs的表观黏度则较原TG交联RDP小。     

真空冷冻与喷雾干燥对鸡蛋全蛋粉理化性质及超微结构的影响

本文以鲜蛋为原料,目的是比较两种干燥方式对全蛋粉的理化性质和功能性质的影响。采用的方法是使用喷雾干燥与真空冷冻干燥两种干燥方式制备全蛋粉并对干燥后得到的全蛋粉的理化性质和功能性质进行了对比研究,探讨了两种干燥方式对全蛋粉的水分含量,水分活度,颗粒分布情况,溶解度,起泡性,乳化性的影响。同时分析比较了两种干燥方式制备的全蛋粉的微观结构图。结果表明,两种干燥方式制成的全蛋粉水分含量和水分活度差异不显著(p0.05),冷冻干燥全蛋粉的溶解度为93.32%,喷雾干燥全蛋粉溶解度87.88%,真空冷冻干燥全蛋粉的乳化活性和起泡力的最大值分别为0.338,62.6%,喷雾干燥全蛋粉的乳化活性和起泡力的最大值为0.248,53.4%。数据表明真空冷冻干燥制成的全蛋粉功能性质优于冷冻干燥制成的全蛋粉。而两种干燥方式制成的全蛋粉的颗粒分布情况与微观结构表征也存在显著差异。     

Blocked Lysine in Dairy Products: Formation,Occurrence, Analysis,and Nutritional Implications

Lysine residues in milk proteins become “blocked” when they react with reducing sugars, particularly lactose, in the Maillard reaction. The blocked or glycated lysines reduce the biological availability of the lysine to metabolic processes and also hinder hydrolysis of the parent protein by digestive enzymes. Heating and storage of milk and milk products are the major promotants of the Maillard reaction and resulting chemical damage to the proteins. Several methods have been proposed to estimate the extent of this protein damage. Two major compounds, furosine, a product of acid hydrolysis of lactulosyl‐lysine, the 1st stable product of the Maillard reaction, and carboxymethyl‐lysine are used for assessing the early and advanced stages of the Maillard reaction, respectively. In addition, several methods are used for assessing the bioavailability of lysine in a protein; these include chemical, enzymic, and animal‐based methods. This review discusses the Maillard reaction and its significance in milk and dairy products, methods of assessing the extent of the reaction and of the bioavailability of lysine, and the nutritional significance of blocked lysines and associated Maillard reaction products in milk proteins.     

Functional properties of isolated porcine blood proteins

The isolated proteins contained in the blood from slaughterhouses could be recovered and used to improve the functional and nutritional properties of food products. In this work some functional properties, namely solubility, emulsifying capacity, gelling and foaming capacity have been tested for different protein fractions of porcine blood. The blood proteins studied were globins (α, β and γ), albumin and fibrinogen and the whole plasma from the plasmatic fraction, and haemoglobin and globin obtained from the haemoglobin by a chemical method from the cellular fraction. The effect of pH and protein concentration on functional properties was determined. Results indicate that blood proteins present good functional properties specially solubility, gellation and emulsifying capacities that could make blood protein useful as food additives in the formulation of food products.     

A comparison of the buttermilk solids functional properties to nonfat dried milk,soy protein isolate,dried egg white,and egg yolk powders

Physicochemical (i.e., sulfhydryl group, protein, and total solubility) as well as functional properties (i.e., water-holding and fat-absorption capacity, foaming and emulsification capacity, and stability) of commercial buttermilk solids (BMS) were compared to nonfat dried milk, soy protein isolate, and dried egg yolk and egg white powders on an equivalent protein basis. BMS showed limited functional properties in water-holding capacity (0.75 g water/g protein) and fat-absorption capacity (1.2 g of oil/g of protein), and foaming capacity (0.5 ml of foam/ml of solution) and stability. However, emulsifying capacity and stability of BMS was not significantly different from other dried protein powders. Results indicated that 0.9 g of protein (approximately 0.45%, wt/vol, concentration) from BMS was needed to emulsify a maximum oil concentration of 50% in water at temperatures up to 50 degrees C. Denaturation of protein, quantified by free sulfhydryl groups, was a critical factor affecting the functionality of BMS and all other protein powders tested. The milk fat globule membrane present in BMS did not enhance either emulsifying capacity or stability.     

钙与乳蛋白的相互作用机制及对其功能特性的影响研究进展

钙作为人体骨骼生长和调节生理功能的重要物质,广泛存在于乳品中。钙与乳中蛋白质如αs-酪蛋白、β-酪蛋白、κ-酪蛋白、α-乳白蛋白和β-乳球蛋白等发生相互作用,影响乳蛋白的结构稳定性,进而使其热稳定性、乳化性、溶解性、起泡性和凝胶性发生改变。本文综述了钙与各种乳蛋白之间的相互作用机制以及对其功能特性的影响,对系统理解钙与乳蛋白的结合具有重要意义,为钙类功能性乳品的深入研究以及工业化生产提供理论依据。     

Spray-dried conjugated linoleic acid encapsulated with Maillard reaction products of whey proteins and maltodextrin

Encapsulation performance of Maillard reaction products (MRPs) produced by whey proteins and maltodextrin were examined for microencapsulation of conjugated linoleic acid (CLA) using spray-drying. CLA was encapsulated using 3 different wall materials containing a single constituent such as whey protein concentrate (WPC), whey protein isolate (WPI), and maltodextrin (MD), and 4 different MRPs. For the development of MRPs, ratios of WPC to MD were 1:2 and 1:3, whereas those of WPI to MD were 1:5 and 1:10. CLA and wall material were mixed and homogenized, and then spraydried. The physical properties of encapsulated CLA powders were characterized by particle size and morphology, ζ-potential, flowability, solubility, and dispersibility. The CLA powders coated with WPI-based MRPs have better encapsulation efficiency, water solubility, and smaller particle size than those coated with WPI, WPC, or MD alone. These encapsulated CLA powders have a number of possible utilities as ingredients in a variety of foods.     

Milk proteins: physicochemical and functional properties

Because of the growing trend toward widespread use of protein ingredients in food formulation and fabrication, an understanding of the relationships between the physical properties of proteins and their behavior in food systems is desirable. A range of milk-derived protein preparations, i.e., dry milk, milk proteins, caseins, whey proteins, and lactalbumin, are used in a range of food products for their specific functional attributes. In this paper some of the apparent relationships between the properties of the protein components and specific functional properties are discussed. Thus, the roles of milk proteins in determining some important physical characteristics (i.e. color, bulk density, sinkability, dispersibility) of milk powders and their involvement in a range of functional properties (water holding, solubility, rheological behavior, gelation, film formation, emulsification, and foaming) are reviewed. Because of the various methods and conditions used in determining functional properties and the variability in composition of preparations it is difficult to compare data and/or reconcile differences in published information. The desirability of developing standard methods is emphasized.     

Baby foods: formulations and interactions (a review)

Infant foods have a special place among food products mainly because of nutritional aspects and preparations methods. A great increase of baby foods incomes is predicted in near future. Formulation, handling, and storage of baby foods are important to keep nutritional quality and physicochemical properties of these foods. During storage some reactions and interactions occur which change physicochemical and nutritional properties of baby foods. Lactose crystallization, Maillard reaction, oxidation, and interactions between micronutrients and other components are the most important aspect of preparation and storage of baby foods. These reactions and interactions influence physical properties such as flowability of powder, solubility, and other functional properties. Controlling of storage conditions such as temperature and moisture content and oxygen quantity in headspace of product is required to keep product quality. In this paper the composition and interactions of baby foods between major components and their effect on nutritional quality of baby foods are explained.     

Interface-related attributes of the Maillard reaction-born glycoproteins

Interfacial behavior of proteins which is a chief parameter to their emulsifying and foaming properties can be tailored through the Maillard reaction. The reaction can increase protein solubility at isoelectric point and ought to be controlled for example by high pressure processing to suppress melanoidins formation. Branched and long saccharides bring considerable steric hindrance which is associated with their site of conjugation to proteins. Conjugation with high molecular weight polysaccharides (such as 440 kDa dextran) may indeed increase the thickness of globular proteins interfacial film up to approximately 25 nm. However, an overly long saccharide can shield protein charge and slow down the electrophoretic mobility of conjugate. Maillard conjugation may decrease the diffusion rate of proteins to interface, allowing further unfolding at interface. As well, it can increase desorption iteration of proteins from interface. In addition to tempering proteins adsorption to interface, Maillard conjugation influences the rheology of protein membranes. Oligosaccharides (especially at higher glycation degrees) decrease the elastic modulus and Huggins constant of protein film; whereas, monosaccharides yield a more elastic interface. Accordingly, glycation of random coil proteins has been exploited to stiffen the corresponding interfacial membrane. Partial hydrolysis of proteins accompanied with anti-solvent-triggered nanoparticulation either before or after conjugation is a feasible way to enhance their emulsifying activity.     

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.