Electrodialytic phenomena and their applications in the dairy industry: a review

Electrodialysis (ED) is an electrochemical separation process by which electrically-charged species are transportedfrom one solution to another ED is a combined method of dialysis and electrolysis and can be performed with two main cell types: multi-membrane cells for dilution-concentration and water dissociation applications (membrane phenomena), and electrolysis cells for redox reactions (electrode phenomena). The dilution-concentration principle applications in the dairy industry consist mainly of the demineralization of milk or milk by-products. The use of ED with monopolar membrane for protein separation and acid caseinate production, and in bioreactors for organic acid production, is also studied in the dairy industry. The interest of ED as a membrane process has been triggered recently by the development of a new membrane type, bipolar membrane. This membrane carries out the dissociation of water molecules. ED with bipolar membranes was applied very recently to the production of lactic acid from whey product fermentation, production of caseinates, and fractionation of whey proteins. Two principle applications of electrode reactions were published: electrochemical coagulation (EC) to precipitate milk proteins, and electroreduction for the reduction of disulfide bonds in the proteins. It appears in this article that processes using membrane phenomena are more numerous and developed than electrolytic applications. This is the composition of milk and the lack of knowledge of redox reactions of the different food compounds that limit the applications and the development of electrolytic phenomena. Electrodialytic phenomena present a great potential for application in the dairy industry, and more generally, in the food industry; many of these applications have to be discovered.     

Electrodialytic phenomena and their applications in the dairy industry: a review

Electrodialysis (ED) is an electrochemical separation process by which electrically-charged species are transported from one solution to another ED is a combined method of dialysis and electrolysis and can be performed with two main cell types: multi-membrane cells for dilution-concentration and water dissociation applications (membrane phenomena), and electrolysis cells for redox reactions (electrode phenomena). The dilution-concentration principle applications in the dairy industry consist mainly of the demineralization of milk or milk by-products. The use of ED with monopolar membrane for protein separation and acid caseinate production, and in bioreactors for organic acid production, is also studied in the dairy industry. The interest of ED as a membrane process has been triggered recently by the development of a new membrane type, bipolar membrane. This membrane carries out the dissociation of water molecules. ED with bipolar membranes was applied very recently to the production of lactic acid from whey product fermentation, production of caseinates, and fractionation of whey proteins. Two principle applications of electrode reactions were published: electrochemical coagulation (EC) to precipitate milk proteins, and electroreduction for the reduction of disulfide bonds in the proteins. It appears in this article that processes using membrane phenomena are more numerous and developed than electrolytic applications. This is the composition of milk and the lack of knowledge of redox reactions of the different food compounds that limit the applications and the development of electrolytic phenomena. Electrodialytic phenomena present a great potential for application in the dairy industry, and more generally, in the food industry; many of these applications have to be discovered.     

膜技术在乳品工业中的应用

综述膜的设计及结构,以及膜技术在乳品工业中应用的研究进展。随着膜技术的发展以及人们对乳成分知识的深入了解,膜技术在液态乳的除菌、乳蛋白的分离、干酪的加工、乳清的处理、初乳的处理,乃至干酪盐水及废水处理与纯化等方面的应用日益广泛。膜技术将为提高乳制品质量、新产品开发、提高生产效率及增加产品利润提供新的途径,成为在不破坏乳成分的前提下保证乳制品安全的强有力的加工手段。     

Bioutilisation of whey for lactic acid production

The disposal of whey, the liquid remaining after the separation of milk fat and casein from whole milk, is a major problem for the dairy industry, which demands simple and economical solutions. The bioconversion of lactose present in whey to valuable products has been actively explored. Since whey and whey permeates contain significant quantities of lactose, an interesting way to upgrade this effluent could be as a substrate for fermentation. Production of lactic acid through lactic acid bacteria could be a processing route for whey lactose and various attempts have been made in this direction. Immobilised cell technology has also been applied to whey fermentation processes, to improve the economics of the process. A fermentative means of lactic acid production has advantages over chemical synthesis, as desirable optically pure lactic acid could be produced, and the demand for optically pure lactic acid has increased considerably because of its use in the production of poly(lactic acid), a biodegradable polymer, and other industrial applications. This review focuses on the various biotechnological techniques that have used whey for the production of lactic acid.     

Processing of high-protein yoghurt – A review

High-protein yoghurt has gained increased consumer interest over the recent years, partly driven by improvements in taste and texture; there is also greater scientific evidence on dairy protein health benefits. The protein content of yoghurt can be increased prior to fermentation by addition of dairy powder, evaporation or membrane filtration, or after fermentation by straining, mechanical separation, or membrane filtration. Concentration of yoghurt after fermentation produces large volumes of acid whey, a major concern for the dairy industry; by concentrating prior to fermentation, production of acid whey is avoided. Different processing techniques influence yoghurt composition, structure, rheology, and sensory properties. This review discusses the challenges, opportunities, the influence of macro components in milk and different processing techniques on composition, structure, rheology, and sensory properties of high-protein yoghurt, along with their benefits and drawbacks for the dairy producer.     

Photo-oxidation of whey proteins: Molecular markers of modification

Oxidative damage significantly affects the food industry, with progressive modification of protein foods and ingredients altering structure, shelf-life, digestibility, nutritional value and function. A redox proteomic damage scoring system was applied to profile and track protein primary level photo-oxidative modification in UVB-irradiated bovine milk whey proteins, lactoferrin and β-lactoglobulin. Lactoferrin oxidation increased significantly after ultraviolet B (UVB) exposure, with the redox score increasing from 0.38 in the control to 1.00 in the irradiated sample. β-lactoglobulin oxidation also increased significantly, from a relatively high baseline redox score of 1.07 in the control to 1.67 in the irradiated sample. A potential marker peptides set for tracking photo-oxidation in milk whey proteins was characterised, with six lactoferrin and four β-lactoglobulin peptides identified. This is anticipated to be of significant utility in monitoring and tracking relative levels of modification, and therefore exposure to oxidative insult, in dairy products through processing, storage, and retail and consumer handling.     

Nondairy food applications of whey and milk permeates: Direct and indirect uses

Permeates are generated in the dairy industry as byproducts from the production of high-protein products (e.g., whey or milk protein isolates and concentrates). Traditionally, permeate was disposed of as waste or used in animal feed, but with the recent move toward a “zero waste” economy, these streams are being recognized for their potential use as ingredients, or as raw materials for the production of value-added products. Permeates can be added directly into foods such as baked goods, meats, and soups, for use as sucrose or sodium replacers, or can be used in the production of prebiotic drinks or sports beverages. In-direct applications generally utilize the lactose present in permeate for the production of higher value lactose derivatives, such as lactic acid, or prebiotic carbohydrates such as lactulose. However, the impurities present, short shelf life, and difficulty handling these streams can present challenges for manufacturers and hinder the efficiency of downstream processes, especially compared to pure lactose solutions. In addition, the majority of these applications are still in the research stage and the economic feasibility of each application still needs to be investigated. This review will discuss the wide variety of nondairy, food-based applications of milk and whey permeates, with particular focus on the advantages and disadvantages associated with each application and the suitability of different permeate types (i.e., milk, acid, or sweet whey).     

Invited review: Acid whey trends and health benefits

In recent years, acid whey production has increased due to a growing demand for Greek yogurt and acid-coagulated cheeses. Acid whey is a dairy by-product for which the industry has long struggled to find a sustainable application. Bulk amounts of acid whey associated with the dairy industry have led to increasing research on ways to valorize it. Industry players are finding ways to use acid whey on-site with ultrafiltration techniques and biodigesters, to reduce transportation costs and provide energy for the facility. Academia has sought to further investigate practical uses and benefits of this by-product. Although modern research has shown many other possible applications for acid whey, no comprehensive review yet exists about its composition, utilization, and health benefits. In this review, the industrial trends, the applications and uses, and the potential health benefits associated with the consumption of acid whey are discussed. The proximal composition of acid whey is discussed in depth. In addition, the potential applications of acid whey, such as its use as a starting material in the production of fermented beverages, as growth medium for cultivation of lactic acid bacteria in replacement of commercial media, and as a substrate for the isolation of lactose and minerals, are reviewed. Finally, the potential health benefits of the major protein constituents of acid whey, bioactive phospholipids, and organic acids such as lactic acid are described. Acid whey has promising applications related to potential health benefits, ranging from antibacterial effects to cognitive development for babies to human gut health.     

Global Market for Dairy Proteins

This review examines the global market for dairy ingredients by assessing the global demand for dairy products in relation to major dairy ingredient categories. Each broad category of dairy ingredients is reviewed including its definition, production and trade status, key applications, and future trends. Ingredient categories examined include whole and skim milk powders (WMPs, SMPs), whey protein concentrates (WPCs) and whey protein isolates (WPIs), milk protein concentrates (MPCs) and milk protein isolates (MPIs), caseins, and caseinates. Increases in world population and improvements in socioeconomic conditions will continue to drive the demand for dairy products and ingredients in the future. Dairy proteins are increasingly recognized to have nutritional and functional advantages compared to many protein sources, and the variety of ingredients with different protein concentrations, functionality, and flavor can meet the needs of the increasingly global dairy consumption. A thorough understanding of the variety of ingredients, how the ingredients are derived from milk, and how the demand from particular markets affects the supply situation are critical elements in understanding the current ingredient marketplace.     

Major advances in concentrated and dry milk products, cheese, and milk fat-based spreads

Advances in dairy foods and dairy foods processing since 1981 have influenced consumers and processors of dairy products. Consumer benefits include dairy products with enhanced nutrition and product functionality for specific applications. Processors convert raw milk to finished product with improved efficiencies and have developed processing technologies to improve traditional products and to introduce new products for expanding the dairy foods market. Membrane processing evolved from a laboratory technique to a major industrial process for milk and whey processing. Ultra-filtration and reverse osmosis have been used extensively in fractionation of milk and whey components. Advances in cheese manufacturing methods have included mechanization of the making process. Membrane processing has allowed uniform composition of the cheese milk and starter cultures have become more predictable. Cheese vats have become larger and enclosed as well as computer controlled. Researchers have learned to control many of the functional properties of cheese by understanding the role of fat and calcium distribution, as bound or unbound, in the cheese matrix. Processed cheese (cheese, foods, spreads, and products) maintain their importance in the industry as many product types can be produced to meet market needs and provide stable products for an extended shelf life. Cheese delivers concentrated nutrients of milk and bio-active peptides to consumers. The technologies for the production of concentrated and dried milk and whey products have not changed greatly in the last 25 yr. The size and efficiencies of the equipment have increased. Use of reverse osmosis in place of vacuum condensing has been proposed. Modifying the fatty acid composition of milkfat to alter the nutritional and functional properties of dairy spread has been a focus of research in the last 2 decades. Conjugated linoleic acid, which can be increased in milkfat by alteration of the cow's diet, has been reported to have anticancer, anti-atherogenic, antidiabetic, and antiobesity effects for human health. Separating milk fat into fractions has been accomplished to provide specific fractions to improve butter spreadability, modulate chocolate meltability, and provide texture for low-fat cheeses.     

牛乳中不同部分蛋白质的组成及功能分析

本研究通过SDS-PAGE电泳将牛乳中不同蛋白质组成部分进行分离鉴定发现,乳脂肪球膜中存在201种蛋白,乳清中存在96种蛋白,酪蛋白中存在21种蛋白,乳粒中存在43种蛋白,其中有27种相同表达的蛋白。通过GO功能注释分析发现,在生物过程中乳脂肪球膜蛋白发挥的作用大于乳清、乳粒蛋白,尤其是生物的调控作用;在分子功能上,牛乳蛋白的主要分子功能是结合作用,其中乳脂肪球膜蛋白的结合作用最强;而乳粒蛋白参与的转运活性分子功能大于乳脂肪球膜、乳清蛋白。在细胞组成上,与乳清、乳粒蛋白相比乳脂肪球膜蛋白参与的细胞组成均较多,而在细胞膜的组成上乳粒蛋白参与较多。通过京都基因与基因组百科全书(KEGG)代谢通路分析可知,乳脂肪球膜、乳清、乳粒中的蛋白均参与过氧化物酶体增殖物激活受体信号通路。对牛乳蛋白质组成进行研究,不仅能够增加牛乳的利用率,并且为日后以乳脂肪球膜、乳粒蛋白作为原料生产乳制品提供理论依据。     

Anticipating market effects of new uses for whey and evaluating returns to research and development

As U.S. dairy farms continue to become more productive, increasing demand is a key to improved economic prospects for the dairy industry. One way to expand demand for dairy products is to find new, economically viable uses for milk. Ex ante economic analysis of new uses for agricultural products anticipates the potential market effects of innovations, and provides a basis for evaluating investment in research and development and setting research priorities. This study evaluated potential economic effects of new applications of films and coatings made from whey protein. An economic simulation model was used to predict the likely effects of the innovations on dairy markets. Cost comparisons with existing technologies and interviews with industry officials were the basis for evaluating potential for commercial adoption of the innovations. The economic simulation model traces the projected increased demand for whey through the markets for dairy products and milk. The associated increased demand for milk could result in benefits to U.S. milk producers of $123.0 million in present value terms, compared to a research cost of $ 4.9 million, with the dairy industry, consumers, and taxpayers all contributing. Interpreting the cost of the research program as an investment on behalf of milk producers, the benefits to producers from development of new whey uses represent an annual rate of return between 28 and 33%. These results are useful for evaluating further investment in the whey research program. The methods illustrated here are applicable to the evaluation of a wide range of research and promotion efforts.     

Size classification of precipitated calcium phosphate using hydrocyclone technology for the recovery of minerals from deproteinised acid whey

Acid whey is generated during the manufacture of acidified dairy products, such as soft cheeses, acid casein ingredients and strained yoghurts. Examples of these whey‐based by‐products include Cottage cheese acid whey and Greek yoghurt acid whey. Alkalisation of acid whey at elevated temperatures (60 °C) precipitates calcium phosphate, which can be recovered and used as an ingredient. The novel application of a liquid–solid hydrocyclone in the size classification of calcium phosphate from heated and neutralised acid whey was investigated in this study. Factors influencing hydrocyclone performance were tested, and the technology was integrated into a membrane filtration‐based process for the production of milk mineral powders.     

Effect of pH at pressure treatment on the acid gelation of skim milk

Skim milk at pH between 6.4 and 7.3 was pressure treated at 200–600 MPa for 30 min and then slowly acidified with glucono-δ-lactone to form acid gels. Milks at low pH produced acid gels with low elastic moduli (final G′) and yield stresses and those at higher pH produced acid gels with higher final G′ and yield stresses. Pressure treatment disrupted the casein micelles at all pH and transferred high levels of casein to the serum phase. Denaturation of α-lactalbumin occurred at a pressure of 600 MPa only, and the level of denaturation increased with increasing pH. Denaturation of β-lactoglobulin (β-LG) occurred at all pressures, with the level of denaturation increasing with the magnitude of the pressure treatment and with pH. The denaturation of the whey proteins and the disruption of the casein micelles could not entirely account for the changes in the rheological properties of the acid gels, as denaturation of up to 50% of the whey proteins produced acid gels with very low final G′ and yield stresses. It is proposed that the pH and the magnitude of the pressure treatment affect the interactions of the denatured β-LG with the casein proteins in the pressure-treated milks, and that this affects the ability of the denatured β-LG to participate in the acid gel structures.Industrial relevanceThe control and manipulation of the firmness of acid skim milk gels is important in many dairy food applications such as yogurts and some types of cheeses. This study has demonstrated that acid gel firmness can be substantially manipulated when the milk is pH adjusted and pressure treated before acidification, and that these effects are different to those obtained through heating. The commercial uptake of high pressure processing in the dairy industry is dependent on this technology producing unique functional properties in milk when compared with traditional processing. The results of this study indicates that high pressure processing of milk may offer unique functional properties in acid gel applications which could be used for the development of new or improved dairy products.     

牛初乳与牛乳中乳清蛋白质组成及功能的对比分析

乳清富含多种功能特性和生物活性的蛋白质,本研究利用SDS-PAGE电泳将牛初乳与牛乳中乳清蛋白质的组成部分进行分离鉴定,发现牛初乳与牛乳中乳清蛋白质的组成存在较大的差异,且在牛初乳乳清中鉴定出290种蛋白,牛乳乳清中鉴定出325种蛋白。由GO功能注释分析发现,在生物过程中,牛初乳乳清蛋白在细胞定位建立和细胞定位中的作用略高于牛乳乳清蛋白。在分子功能上酶抑制活性作用是牛初乳乳清蛋白和牛乳中乳清蛋白的主要分子功能。在细胞组成上牛初乳乳清蛋白参与较多的是细胞外部分和细胞外空隙,与牛乳乳清蛋白相比参与的细胞组成大体相同。通过KEGG代谢通路分析可知,牛初乳和牛乳乳清蛋白均参与过补体及凝血级联反应通路。对牛初乳乳清蛋白组成进行研究,不仅能够增加牛初乳的利用率,并且为日后以乳清蛋白作为原料生产乳制品提供理论依据。     

Effects of high pressure,microwave and ultrasound processing on proteins and enzyme activity in dairy systems — A review

High-pressure processing (HPP), microwaves (MW) and ultrasound (US) are used for pasteurization with minimum heat input. They also alter physico-chemical properties of milk proteins and enzymes. This article aims at identifying the important changes in milk proteins imparted by these three processing technologies. HPP dissociates casein micelles at low pH (<6.7) and concentrations (<4% w/w), while β-LG is the most pressure sensitive whey protein due to the presence of free thiol groups. Milk enzyme activity is inhibited at higher pressures (>400 MPa). MW treatment denatures whey proteins rapidly, even below their thermal denaturation temperatures. High-power MW treatment (e.g. 60 kW) deactivates enzymes by denaturing them. However, low-power controlled MW irradiation (e.g. 30 W) improves enzyme activity. Ultrasound can homogenize protein aggregates in dairy systems and cause whey protein denaturation. Sonication under applied pressure and heat (e.g. 3.5 kg/cm², 126.5 °C) causes enzyme inhibition while mild sonication conditions can improve enzyme activity.Industrial relevanceHPP, MW and US are gaining popularity in the dairy industry due to their ability to pasteurize and functionalize dairy streams with minimal heat input. This review offers insights into how these technologies can be used in isolation or in combination to alter milk proteins and enzyme activity for different academic and industrial applications. However, to fully understand the potential of HPP, MW and US treatment on dairy systems, further research is required in several areas including health related nutritional changes in milk and milk products caused by these technologies.     

蛋白质组学技术及其在乳及乳制品中的应用研究进展

蛋白质组学技术是近年来生命科学研究的重要工具,在食品、医学及动植物研究领域具有独特优势。利用蛋白质组学技术研究乳及乳制品,深入阐明其中蛋白质的表达及动态变化已成为当前的研究热点。该文主要综述了蛋白质组学的概念、常用技术及应用领域,重点介绍蛋白质组学在乳及乳制品领域,特别是在乳脂肪球膜蛋白、乳清蛋白、乳及乳制品加工过程以及干酪制品中的研究应用,探讨了目前乳及乳制品蛋白质组学研究中存在的问题与局限,并对蛋白质组学及其在乳及乳制品中的应用前景进行了总结与展望,为应用蛋白质组学技术深入研究乳及乳制品提供了理论依据。     

Performance assessment of membrane distillation for skim milk and whey processing

Membrane distillation is an emerging membrane process based on evaporation of a volatile solvent. One of its often stated advantages is the low flux sensitivity toward concentration of the processed fluid, in contrast to reverse osmosis. In the present paper, we looked at 2 high-solids applications of the dairy industry: skim milk and whey. Performance was assessed under various hydrodynamic conditions to investigate the feasibility of fouling mitigation by changing the operating parameters and to compare performance to widespread membrane filtration processes. Whereas filtration processes are hydraulic pressure driven, membrane distillation uses vapor pressure from heat to drive separation and, therefore, operating parameters have a different bearing on the process. Experimental and calculated results identified factors influencing heat and mass transfer under various operating conditions using polytetrafluoroethylene flat-sheet membranes. Linear velocity was found to influence performance during skim milk processing but not during whey processing. Lower feed and higher permeate temperature was found to reduce fouling in the processing of both dairy solutions. Concentration of skim milk and whey by membrane distillation has potential, as it showed high rejection (>99%) of all dairy components and can operate using low electrical energy and pressures (<10 kPa). At higher cross-flow velocities (around 0.141 m/s), fluxes were comparable to those found with reverse osmosis, achieving a sustainable flux of approximately 12 kg/h·m² for skim milk of 20% dry matter concentration and approximately 20 kg/h·m² after 18 h of operation with whey at 20% dry matter concentration.     

膜技术在乳品工业中应用的最新进展

综述了膜技术的特点、分离机理、分类和在乳品工业中的应用,以及膜技术在乳品除菌、回收产品、乳清脱盐、牛乳的浓缩、乳蛋白浓缩、乳蛋白质分级分离、乳的标准化以及在酸乳和干酪制造等方面的应用。阐述了膜分离技术可简化生产工艺、提高效率、提高乳成分综合利用率,而且可以降低能耗、减少废水污染,因而具有显著的经济效益和环保作用,具有很好的发展和应用前景。同时也对存在的问题进行了分析。     

Maximizing the value of milk through separation technologies.

Milk is the source of a wide range of proteins that deliver nutrition to the most promising new food products today. Isolated milk proteins are natural, trusted food ingredients with excellent functionality. Separation technologies provide the basis for adding value to milk through the production of proteins that provide the food industry with ingredients to meet specific needs, not possible with milk itself or with other ingredients. The major milk proteins, casein and whey protein, can be isolated by manipulating their compositional and physical properties and then by using various separation technologies to recover the proteins. Additionally, they can be processed in various ways to create a wide range of ingredients with diverse functional characteristics. These ingredients include milk protein concentrate, milk protein isolate, casein, caseinate, whey protein concentrate, whey protein isolate, hydrolysates, and various milk fractions. Within each of these ingredient categories, there is further differentiation according to the functional and nutritional requirements of the finished food. Adding value to milk by expanding from consumer products to ingredients often requires different technologies, marketing structure and distribution channels. The worldwide market for both consumer products and ingredients from milk continues to grow. Technology often precedes market demand. Methods for the commercial production of individual milk components now exist, and in the future as clinical evidence develops, the opportunity for adding value to dairy products as functional foods with health benefits may be achieved. The research and development of today will be the basis of those value-added milk products for tomorrow.