蛋白质和多糖在界面处的相互作用研究进展

蛋白质和多糖两种生物大分子在界面处的相互作用对于乳状液和泡沫体系有显著影响。蛋白质和多糖混合后的协同效应可构建新的、功能性的纳、微或宏观结构,改变食品的力学和流动特性,对改良食品,降低生产成本具有重要意义。本文对近年来蛋白质的界面行为,多糖的界面行为以及蛋白质-多糖复合物的界面行为所做的一些研究进行综述。      

Colorimetric analysis of protein sulfhydryl groups in milk: applications and processing effects

Methods for protein sulfhydryl (SH) group analysis in food systems have been largely overlooked. Nevertheless, changes in SH group concentration affect both physical and nutritional characteristics of high protein foods and ingredients. Food scientists and technologists require improved understanding of protein SH chemistry in order to design processes that minimize loss of thiol groups. This article surveys colorimetric methods for food protein SH group analysis with applications to fluid milk and dried milk powder. Most colorimetric assays (chloromeribenzoate, pyridine disulfide, Nitrobenzo-2-oxa-1,3-diazole, papain reactivation assay, etc.) were found to be inferior to the Ellman method based on the use of 5,5'dithio (bis-2 nitro benzoic acid). Techniques for SH group analysis in fluid milk and dried milk powder are described, along with typical results, their interpretations, and current research related to processing effects and the role of milk SH content on a wider range of technological issues, such as development of cooked flavors, fouling and cleaning of plate heat exchanges, protein-protein interactions, and the storage stability. Finally, a number of areas requiring further research are presented.     

Isolation,purification, and alteration of some functional groups of major milk proteins: A review

This review covers selected methods of isolation and purification of mainly α_s‐casein, β‐casein, κ‐casein, β‐lactoglobulin, and α‐lactalbumin. Selected methods of alteration of some functional groups of these proteins also were reviewed. Isolation and purification of milk proteins per se are methods of modifying the individual milk proteins. Gram quantities of these proteins can now be purified in a relatively short time using ion‐exchange resins. Due to the prominent use of non‐food‐grade reagents in the procedures for preparation of these milk proteins, individual proteins are not maximally utilized for the manufacture of food/feed and pharmaceutical products. Therefore, intensive research efforts are needed to obviate the problems associated with underutilization of milk proteins.     

Prevention of lipid oxidation in muscle foods by milk proteins and peptides: A review

Muscle foods (especially fresh meat, precooked, and restructured meat products) are highly prone to lipid oxidation, which ultimately leads to certain problems, viz. discoloration, off-flavor, drip losses, loss of essential fatty acids and vitamins, and generation of toxic products. These problems can be minimized with the help of various agents and or techniques such as use of natural/synthetic antioxidants, metal chelating agents, physical conditions, vacuum packaging, and encapsulation techniques. Among these, the role of synthetic antioxidants is quite debatable due to certain health risks to humans. Among the natural molecules, milk proteins and their bioactive peptides offer a promising potential for the meat industry. Various forms of milk proteins and peptides including caseinates, whey proteins, skim milk, and milk co-precipitates can be used to prevent lipid oxidation in meat products either in the form of added ingredients or as edible coatings. However, in addition to prevention of lipid oxidation, they also provide nutritional benefits and improve the technological processing and shelflife of meat and meat products. This review focuses on the utilization, mechanism of action, and efficacy of milk proteins and peptides to inhibit lipid oxidation in muscle food products.     

Interactions between milk proteins and gellan gum in acidified gels

The mechanical properties, microstructure and water holding capacity of systems formed from whey protein concentrate (0–3% WPC w/w), sodium caseinate (0–2% w/w), and gellan gum (0.1–0.3% w/w) in the coil or helix conformational state (Coil/Helix), were investigated. This polymer combination resulted in bi-polymeric or tri-polymeric systems, which were slowly acidified to pH 4.0 by the addition of GDL in order to favor electrostatic protein–polysaccharide interactions. The properties of the tri-polymeric systems differed considerably from the bi-polymeric ones. At high polymer concentrations the WPC-gellan samples showed incompatibility and microphase separation, which resulted in weaker and less deformable gels. However, in systems with coil gellan the incompatibility was less intense, which was attributed to the formation of electrostatic complexes between the protein and the polysaccharide during the mixing process. In caseinate–gellan systems, complex formation was observed and an increase in the gel mechanical properties as the caseinate concentration rose, although the water holding capacity decreased at higher gellan concentrations. The caseinate–gellan coacervate was not visualized in the tri-polymeric systems and the incompatibility between the biopolymers was intensified, although the mechanical properties were considerably higher than in the bi-polymeric gels.     

Electrostatic interaction between proteins and polysaccharides: Physicochemical aspects and applications in emulsion stabilization

Colloidal particle systems based on natural biopolymers are widely used in food industries and their production can involve an emulsification step during processing, which is induced by interaction of a primary emulsion, in which oil droplets are emulsified by a protein, with a stabilizing polysaccharide. This review highlights the physical and chemical aspects involved in the electrostatic interaction between proteins and polysaccharides, their application in emulsion stabilization, and processing alternatives for their production. Emphasis is given on applications and chemical characteristics of whey protein concentrate, soy protein isolate, pectin, and sodium alginate, that is, biopolymers often applied in emulsion formulations.     

The balance between caseins and whey proteins in cow's milk determines its allergenicity

Cow's milk allergy is quite common in the first years of human life. Protein composition plays an important role in this pathology, particularly the casein/whey protein ratio. It is known that milks from different species have different sensitization capacities although their protein sources are quite similar. Thus, the objective of this work was to compare the allergenicity of native cow's milk and milk with a modified ratio of casein and whey proteins in a murine model of atopy. Twenty-four Balb/c mice were orally sensitized to native cow's milk or modified cow's milk with a casein/whey protein ratio of 40:60. During the sensitization period, the number of mice suffering from diarrhea was significantly higher in the native cow's milk-sensitized group than in the modified milk-sensitized group. Once mice were killed, plasma histamine levels were shown to be significantly higher in native cow's milk-sensitized mice. In addition, cow's milk proteins induced a higher lymphocyte sensitization in the native milk-sensitized mice, with a significant increase in the specific proliferation ratio of these cells.These results suggest that the balance between caseins and whey proteins plays an important role in the sensitization capacity of cow's milk, and its modification might be a way to reduce the allergenicity of cow's milk.     

Properties of bread dough with added fiber polysaccharides and phenolic antioxidants: a review

During breadmaking, different ingredients are used to ensure the development of a continuous protein network that is essential for bread quality. Interests in incorporating bioactive ingredients such as dietary fiber (DF) and phenolic antioxidants into popular foods such as bread have grown rapidly, due to the increased consumer health awareness. The added bioactive ingredients may or may not promote the protein cross-links. Appropriate cross-links among wheat proteins, fiber polysaccharides, and phenolic antioxidants could be the most critical factor for bread dough enhanced with DF and phenolic antioxidants. Such cross-links may influence the structure and properties of a bread system during baking. This article presents a brief overview of our current knowledge of the fate of the key components (wheat proteins, fibers, and phenolic antioxidants) and how they might interact during bread dough development and baking.     

Utilization of two plant polysaccharides to improve fresh goat milk cheese: Texture,rheological properties,and microstructure characterization

This study aimed to evaluate the effects of added jujube polysaccharide (JP) and Lycium barbarum polysaccharide (LBP) on the texture, rheological properties, and microstructure of goat milk cheese. Seven groups of fresh goat milk cheese were produced with 4 levels (0, 0.2, 0.6, and 1%, wt/wt) of JP and LBP. The goat milk cheese containing 1% JP showed the highest water-holding capacity, hardness, and the strongest rheological properties by creating a denser and more stable casein network structure. In addition, the yield of goat milk cheese was substantially improved as a result of JP incorporation. Cheeses containing LBP expressed lower fat content, higher moisture, and softer texture compared with the control cheese. Fourier-transform infrared spectroscopy and low-field nuclear magnetic resonance analysis demonstrated that the addition of JP improved the stability of the secondary protein structure in cheese and significantly enhanced the binding capacity of the casein matrix to water molecules due to strengthened intermolecular interactions. The current research demonstrated the potential feasibility of modifying the texture of goat milk cheese by JP or LBP, available for developing tunable goat milk cheese to satisfy consumer preferences and production needs.     

Invited review: Microfiltration-derived casein and whey proteins from milk

Milk, a rich source of nutrients, can be fractionated into a wide range of components for use in foods and beverages. With advancements in filtration technologies, micellar caseins and milk-derived whey proteins are now produced from skim milk using microfiltration. Microfiltered ingredients offer unique functional and nutritional benefits that can be exploited in new product development. Microfiltration offers promise in cheesemaking, where microfiltered milk can be used for protein standardization to improve the yield and consistency of cheese and help with operation throughputs. Micellar casein concentrates and milk whey proteins could offer unique functional and flavor properties in various food applications. Consumer desires for safe, nutritious, and clean-label foods could be potential growth opportunities for these new ingredients. The application of micellar casein concentrates in protein standardization could offer a window of opportunity to US cheese makers by improving yields and throughputs in manufacturing plants.     

国内外法规对水解乳蛋白在婴幼儿配方食品中使用的规定

目的整理分析国内外对水解乳蛋白在婴幼儿配方食品中的应用规定及研究文献,为该类产品的研发、使用和监管提供参考。方法系统整理国内外水解乳蛋白在婴幼儿配方食品中使用的相关研究、法律法规和临床应用,并结合我国现状进行讨论分析。结果通过整理比较,我国相关法规及标准明确了水解乳蛋白在特殊医学用途婴儿配方食品中使用的技术要求;国际法典委员会和欧盟也对水解乳蛋白在婴儿配方食品中的使用有相应规定;美国虽未出台具体法规,但有大量的权威文献及科学研究资料;中国台湾地区食品标准对水解乳蛋白的使用要求与国际法典委员会一致;澳大利亚/新西兰、日本等国家和地区暂未查询到相关规定。结论我国应当借鉴国际先进经验,加强水解乳蛋白的基础性研究和临床研究,不断完善相关标准、法规和技术要求,促进并规范水解乳蛋白在婴幼儿配方食品中的应用。     

Calcium: A comprehensive review on quantification,interaction with milk proteins and implications for processing of dairy products

Calcium (Ca) is a key micronutrient of high relevance for human nutrition that also influences the texture and taste of dairy products and their processability. In bovine milk, Ca is presented in several speciation forms, such as complexed with other milk components or free as ionic calcium while being distributed between colloidal and serum phases of milk. Partitioning of Ca between these phases is highly dynamic and influenced by factors, such as temperature, ionic strength, pH, and milk composition. Processing steps used during the manufacture of dairy products, such as preconditioning, concentration, acidification, salting, cooling, and heating, all contribute to modify Ca speciation and partition, thereby influencing product functionality, product yield, and fouling of equipment. This review aims to provide a comprehensive understanding of the influence of Ca partition on dairy products properties to support the development of kinetics models to reduce product losses and develop added-value products with improved functionality. To achieve this objective, approaches to separate milk phases, analytical approaches to determine Ca partition and speciation, the role of Ca on protein–protein interactions, and their influence on processing of dairy products are discussed.     

Interactions between milk proteins and polyphenols: Binding mechanisms,related changes,and the future trends in the dairy industry

The biological activity and techno-functional properties of phenolic compounds have gained great importance due to the epidemiologically-proved health benefits. Use of polyphenols as fortification agents for functional food production and nanotechnological approaches using natural vehicles for polyphenol delivery have been recently discussed. In this respect, milk proteins and dairy products represent unique characteristics for polyphenol studies. The conflicting results on the functionality of polyphenols interacting with milk proteins either in model systems or in complex dairy matrices reveal the need for future studies.     

Chemical interactions between additives in foodstuffs: a review

This paper critically reviews the key literature on food additive-additive chemical interactions published over the last 30 years together with appropriate relevant information on food additive-food component interactions. Five main classes of food additive are included, reflecting the research effort to date: the sulfur (IV) species of preservatives, synthetic food colouring materials, nitrate and nitrite, ascorbic acid, and sorbic acid. Within each class, aspects of the chemistry (reactivity), functionality, stability, use and reactions with other specific food additives are reviewed. Where appropriate, the importance of interactions of food additives with other components of food (i.e. nutrients and non-nutrients) has been assessed and certain aspects of toxicology included. The practical outcome of this review is presented as a set of recommendations for future research in this area. The use of the data in this review is proposed as a training set to develop the framework into a diagnostic tool. This might be used ultimately for the development of a multilevel framework, operating systematically, to understand the important parameters that dictate the outcome of additive interactions.     

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.     

Improvement of emulsifying properties of milk proteins with κ or λ carrageenan: effect of pH and ionic strength

The objective of this work was to determine the effect of λ‐carrageenan or κ‐carrageenan on the emulsion capacity, emulsion work and emulsion stability of milk proteins concentrate (MP) or sodium caseinate (SC) emulsions at different levels of pH and ionic strength. Incorporation of carrageenans to proteins emulsions resulted in an improvement of emulsifying properties at pH 6.0 and low ionic strength (0.2 m NaCl). Although emulsion capacity was high in MP than for SC, irrespectively of carrageenan employed, addition of λ‐carrageenan increased twofold emulsion work values (15 327 Ω s^?1 for MP and 11 455 Ω s^?1 for SC; around 6000 Ω s^?1 in the other treatments). Emulsion stability was high with λ‐carrageenan (9.8 s) than MP‐κ‐carrageenan or MP (7.45 and 7.40 s, respectively). Carrageenan improving of emulsion properties was because of the complex formation with MP, characteristic of this type of food system when pH was above of isoelectric point.     

Quinoline yellow dye stimulates whey protein fibrillation via electrostatic and hydrophobic interaction: A biophysical study

Amyloid fibril formation of proteins is associated with a number of neurodegenerative diseases. Several small molecules can accelerate the amyloid fibril formation in vitro and in vivo. However, the molecular mechanism of amyloid fibrillation is still unclear. In this study, we investigated how the food dye quinoline yellow (QY) induces amyloid fibrillation in α-lactalbumin (α-LA), a major whey protein, at pH 2.0. We used several spectroscopy techniques and a microscopy technique to explore how QY provokes amyloid fibrillation in α-LA. From turbidity and Rayleigh light scattering experiments, we found that QY promotes α-LA aggregation in a concentration-dependent manner; the optimal concentration for α-LA aggregation was 0.15 to 10.00 mM. Below 0.1 mM, no aggregation occurred. Quinoline yellow–induced aggregation was a rapid process that escaped the lag phase, but it depended on the concentrations of both α-LA and QY. We also demonstrated that aggregation switched the secondary structure of α-LA from α-helices to cross-β-sheets. We then confirmed the amyloid-like structure of aggregated α-LA by transmission electron microscopy measurements. Molecular docking and simulation confirmed the stability of the α-LA-QY complex due to the formation of 1 hydrogen bond with Lys99 and 2 electrostatic interactions with Arg70 and Lys99, along with hydrophobic interactions with Leu59 and Tyr103. This study will aid in our understanding of how small molecules induce aggregation of proteins inside the stomach (low pH) and affect the digestive process.     

Quantitative analysis of differentially expressed milk fat globule membrane proteins between donkey and bovine colostrum based on high-performance liquid chromatography with tandem mass spectrometry proteomics

This study was designed to provide novel insights into milk fat globule membrane (MFGM) proteins in donkey colostrum (DC) and bovine colostrum (BC) using quantitative proteomics. In total, 179 (DC) and 195 (BC) MFGM proteins were characterized, including 71 shared, 108 DC-specific, and 124 BC-specific proteins. Fifty-one shared proteins were selected as differentially expressed MFGM proteins, including 21 upregulated and 30 downregulated proteins in DC. Gene ontology analysis showed that these proteins were mainly enriched in cellular components, including the extracellular exosome, extracellular space, and plasma membrane. Additionally, they were further involved in metabolic pathways, including cholesterol metabolism, the peroxisome proliferator-activated receptor signaling pathway, and purine metabolism. Furthermore, several key protein factors with high connectivity were identified via protein–protein interaction analysis. These results provide more comprehensive knowledge of differences in the biological properties of MFGM proteins in DC and BC as well as pave the way for future studies of the nutritional and functional requirements of these important ingredients toward the development of dairy products based on multiple milk sources.