Concentrates and Dried Products with Milk Components

Approximately 10% of Swiss milk is used directly to manufacture dried-milk products and condensed milk (long-life dairy products). The figure fluctuates between around 8% and 13%, depending on the market situation of milk and dairy products. In 2015, for example, the amount of products containing dried-milk products and condensed milk came to 50,500 tonnes, manufactured from 358,000 tonnes of milk (10.3% of total milk production). Included in this but not listed separately are novel milk proteins, lactose, and other dairy components obtained from skimmed milk, whey or buttermilk. In addition to the quantity of milk for long-life dairy products shown in the statistics of the TSM (=Treuhandstelle Milch GmbH), concentrates and dried-milk products are also manufactured e.g. from skimmed milk, from buttermilk from butter production, and from around 55% of the whey from cheese production.

The range of milk-based food ingredients is wide, and their uses are varied. Skimmed- and whole-milk powder is exported to countries with milk shortages. Powdered whole milk is an important ingredient in Swiss chocolate. Particularly high-quality special protein powders are used for nutraceuticals, sports nutrition, or as a natural emulsifier. A complete food substitute for infants consists of various dried products from milk, such as skimmed-milk powder, whey-protein concentrate, α-lactalbumin, lactose, and in some cases special protein fractions such as lactoferrin. Additional ingredients are used here.

Depending on the product in question, all milk components are either concentrated via dehydration (whole-milk powder), or  individual components such as casein, whey proteins and other high-quality components are selectively separated and concentrated via gentle, innovative membrane separation techniques and further separating processes. In concentrated or powdered form, these products have a long storage life, thanks to their low water content.

7.1 Introduction

In addition to its many valuable components, milk contains a significant proportion of water: 87– 88% (see R. Sieber, Zusammensetzung von Milch (Composition of Milk), Table 14). The partial removal of water from the milk is an important step in improving its keeping qualities.  Condensed milk and other concentrates still contain 25–75% water, and depending on the residual water content and any added sugar, are packed either sterilised in metal cans or pasteurised in large drums or plastic tubes. Dried milk products have a residual water content of around 4%, and may be stored unrefrigerated and without aseptic packaging.

Different methods can be used to remove the water from the milk. One way which has been used for millennia is to curdle the milk and strain out the whey, as done when making cheese. Here, we discuss water extraction by means of evaporation, drying and membrane separation techniques.

Figure 1 and Table 1 show the quantitative importance of long-life milk products (dry products and condensed milk) in Switzerland. It can be seen from these tables that around 10% of the milk marketed in Switzerland reaches the customer as dry products and concentrates. Special products such as milk proteins, lactose, nutraceuticals and infant formulas are not included.

Abbildung_1_Grafik_TSM_2018
Figure 1: Milk produced in Switzerland – a breakdown of use according to product group. Data source: TSM Treuhand GmbH, 27 May 2018

Switzerland produces small quantities of condensed milk for direct consumption. Customised milk concentrates reach the food industry as a semi-finished product. Some of the sweetened and unsweetened condensed milk for the retail trade is imported. Important customers for dried products are the Swiss and foreign food industries (chocolate, baked goods, infant foods, dairies producing mainly yoghurt, ice cream and flavoured milk drinks, foreign cheese factories, sauce and soup manufacturers, meat products, etc.). In Switzerland, only a very small proportion is sold directly to the consumer as milk powder.

Table 2 provides an overview of the rough chemical composition of various milk powders and other dried products.

7.2 Condensed Milk, Concentrates

Condensed milk and milk concentrates are produced from milk or skimmed milk by removing water via evaporation under vacuum at temperatures of 45-80° C in specially designed, product-friendly plants. They are very important as the preliminary stage in milk-powder production. In addition, concentrates are supplied directly to the food industry as semi-finished products in bulk containers or tankers. Condensed milk and sweetened condensed milk are concentrates that are also sold as consumer products. Tinned, sterilised condensed milk is imported. Pasteurised sweetened condensed milk in the tube is still, at least in part, manufactured in Switzerland. Table 3 provides an overview of the composition of condensed milk.

Condensed milk (unsweetened) and sweetened condensed milk in retail packaging are used as an ingredient in various recipes. Unsweetened condensed milk is frequently used as a coffee lightener, although not in Switzerland, where coffee cream has become the norm. Condensed skimmed milk and sweetened condensed skimmed milk are used as semi-finished products in food manufacturing.

7.3 Whole- and Skimmed-Milk Powder

7.3.1 Chemical and physical characteristics of whole-milk and skimmed-milk powder

Important quality parameters for milk powder are microbiological quality, organoleptic characteristics, and physicochemical characteristics as per Table 4 below:

 

Further parameters:

  • Water content
  • Fat content
  • Protein content
  • Mineral content
  • Titratable acid
  • Reconstitutability
  • Heat stress for skimmed-milk powder (fraction of non-denatured whey proteins)
  • Burnt particles
  • Residual oxygen level in the packaging


The drying process has a crucial impact on the product characteristics. A distinction must therefore be made between spray-dried and drum-dried powder. The next chapter goes into these processes in greater detail.

Milk powder must be free-flowing, like sand, and must not form lumps. Its flowability is adversely affected by incompletely crystallised lactose, which absorbs water. Particle size and shape, bulk density and electrical charge also affect flow behaviour.

The milk fat in whole-milk powder or partially skimmed-milk powder can change through oxidation. The presence of high concentrations of oxygen in the packaging, light, metallic ions such as copper and iron, and to a lesser extent other metals, facilitate this oxidation. Table 4 lists the maximum limits for copper and iron content. To prevent oxidation, when packaging milk powders containing fat it is important to exclude oxygen through vacuum-packaging or packaging in a protective-gas atmosphere (nitrogen). The tolerance value is given in Table 4. Proper management of the preheating stage during powder production reduces oxidative changes in the final product.

Burnt particles are caused by a strong Maillard reaction (the reaction of sugars with amino acids, the building-blocks of proteins) during the drying process, when particles remain in the process for too long.
A certain browning due to the Maillard reaction is normal with milk powder. The Maillard reaction is stronger with drum drying than with spray drying. The Maillard reaction continues during storage, which is why storage conditions (temperature, length of storage) are important for preserving the quality of milk powder, and in particular of milk-protein concentrates in powdered form.

7.3.2 Manufacture / Technology

The basic steps in the manufacture of milk powder are concentration by evaporation and drying.

Figure 3 shows the manufacturing process. Milk of high quality is selected. Since the concentration of dissolved and dispersed substances in the milk increases during powder manufacture, the milk must be highly stable; otherwise, the proteins may destabilise and precipitate. An acid level of < 7.5°SH must be required. There must be no contamination with metallic ions, especially copper. The microbial count requirements must be respected. The milk is cleansed of dirt particles in the cleaning centrifuge, cooled, then refrigerated. Depending on the type of powder to be produced, some or all of the milk fat is centrifuged off as cream. The protein content is adjusted to the legal minimum content through the addition of milk components, usually milk- or whey-permeate powder.

A heat treatment ensues with the following aims:

  • Inactivation of all pathogenic bacteria and reduction of overall microbial count
  • Inactivation of the enzymes, especially lipase
  • Activation of SH groups in β-lactoglobulin in order to increase the oxidation stability of the powder during storage.

‘High-short’ processes are preferable, since they achieve the desired effects more gently and form more antioxidative substances. Moreover, the solubility of the powder is better when a ‘high-short’ process is used. Heating often takes place for 15–30 seconds at 88–95 °C, sometimes at temperatures of up to 130 °C.

Abbildung_2_Eindampfanlage_Web
Figure 2: View of a milk evaporation plant (http://www.gea.com/global/en/products/falling-film-evaporator.jsp)

The milk then passes to the evaporation plant. Water is gently evaporated off under vacuum at temperatures of 45–75° C until a concentration of 40–50% milk dry matter is obtained. Through multiple use and thermal or mechanical exhaust-vapour compression, the evaporation plant makes efficient use of energy. (‘Exhaust vapour’ refers to the steam that escapes from the product.) Thanks to thin-film technology, the milk and the resultant concentrate remain only very briefly in the system at a high temperature. Figure 2 shows an evaporation plant, and Figure 4 shows its operating method.

Abb_3_Fliessschema_Trockenprodukte_EN_555

Milk powder which contains fat is partially homogenised during manufacture, in order to reduce the free fat. Free fat with no protective or secondary membrane reduces the solubility of milk powder and increases the risk of fat oxidation. After evaporation, homogenisation is carried out at pressures of 50–150 bar. In the case of powders for chocolate manufacture free fat is desirable, so no homogenisation takes place.

Abbildung 4: Schema eines Fallfilmverdampfers
Figure 4: Diagram of a falling-film evaporator (http://www.gea.com/global/
en/products/falling-film-evaporator.jsp)

A: Milk in-feed
B: Exhaust vapour
C: Milk concentrate
D: Heating steam
E: Steam condensate

1: Evaporator head
2: Calandria
3: Calandria, lower part
4: Mixing channel
5: Exhaust-vapour separator

Drying

Two different main methods are used: drum drying and spray drying. With drum drying, the milk concentrate is spread on a hot surface in a thin layer, causing a large proportion of the water to evaporate within just a few seconds. With spray drying, the milk concentrate is atomised into a hot-air stream, causing the water to evaporate from the droplets.

Drum Drying

Milk concentrate with 45–50% dry matter is spread in a thin layer on the rotating drying rollers, which are heated from inside with steam, and have a temperature of up to 145 °C. Within less than 3 seconds a residual water content of just 4% is reached, and the dried milk is scraped off the rollers with knives. The powder flakes fall into a worm conveyor and are then crushed in a hammer mill, cooled, sieved and lastly packed. Figure 5 is a diagram of a drum dryer. Compared to spray dryers, drum dryers are relatively compact and give a better return on investment.  Figure 7 shows the microstructure of milk powder. The drum-drying process produces flat, flaky particles.

Abbildung_5_Walzentrocknung_Web
Figure 5: Diagram of drum drying
Source: http://www.simon-dryers.co.uk

The drum drying of milk produces certain irreversible changes. The high temperatures cause a denaturing of the milk proteins, lactose caramelisation, and a browning through the Maillard reaction, in which sugar and amino acids react with one another. Owing to protein denaturation, drum-dried powder is less soluble in water than spray-dried powder. The characteristics of drum-dried milk powder are advantageous for certain applications, for example in chocolate manufacturing.

Spray drying

Spray drying is the most common drying method for producing milk powder.

Figure 6 is a diagram of a spray dryer. A spray-nozzle atomiser or rotary atomiser sprays milk concentrate in tiny droplets 50–80mm in diameter into the top of a several-storey-high drying tower. Usually, filtered hot air at a temperature of 150–300 °C is also blown into the top of the tower.  This facilitates gentle drying. Because the round droplets formed during atomisation keep their shape during the drying process, spray-dried powder particles are spherical (see Figure 7).  Air trapped in the particles produces a lower bulk density. The water in the tiny droplets evaporates quickly – within 1/100th to 1/10th of a second – which causes rapid cooling of  the particles and the air. When drying is over, the maximum particle temperature is just 65–75 °C. After discharge from the drying tower and any final drying in the fluid-bed dryer, the powder is separated from the drying air in a several-stage process, also with the aid of cyclones, and cooled with cold air.

 

Abbildung_6_Spruehtrocknungsanlage_Web
Figure 6: Spray dryer, two-stage, with fluid-bed final drying stage at the bottom near the tower. Source: http://www.spxflow.com (Charlotte, North Carolina, USA)
Abbildung 7 zeigt Mikrostruktur von Milchpulver (Elekronenmikroskopische Aufnahme)
Figure 7: Microstructure of milk powder (electron micrograph): on left, drum-dried; on right, spray-dried. Particle size: drum-dried powder, primary particles approx. 250–500 µm, flaky; spray-dried powder, primary particles 25– 50 µm in diameter, spherical. Source: M. Kaláb.

Packaging and storage

Appropriate packaging is important for preserving the quality of milk powder. The packaging must protect the powder from moisture, air, light and contamination, and of course logistical requirements must also be met. Frequent use is made of paper with a bitumen layer, multi-ply cartons or boxes with polyethylene liners, metal drums with polyethylene liners, or tins with aluminium-foil lids. Shelf life can be extended by removing oxygen via a protective-gas atmosphere or vacuum packaging. Milk powder is stored at ambient temperature. Whole-milk powder has a shorter shelf life than skimmed-milk powder because of potential fat oxidation.

7.3.3 Special features of skimmed-milk powder

The flow diagram in Figure 3 shows the differences between the manufacture of skimmed-milk powder and whole-milk powder. For skimmed-milk powder, all the cream is skimmed off, and the heat treatment is either reduced to gentle pasteurisation at low-heat, or extended to 15-30 min. at high heat. The post-evaporation concentration of drum-dried skimmed milk is substantially lower than for full-fat dried milk. Skimmed-milk powder is usually manufactured by the spray-drying method, however.

Low heat / high heat: Skimmed-milk powder is classified according to its heat stress and consequent protein denaturation (cf. Table 5). Low-heat powder is manufactured with the minimum possible heat stress to the milk, the concentrate and the powder. Even at the initial skimming stage, cold-milk separators are used for low-heat powder. The dwell times at elevated temperatures are kept as short as possible. Only gentle pasteurisation is used, rather than a intensive heat treatment. High-heat powder has undergone intensive heating, which denatures the maximum possible number of whey proteins. This is desirable e.g. for use in baked goods. Denatured whey proteins bind a great deal of water.

Rapid cooling after drying is particularly important for skimmed-milk powder, owing to its sensitivity to moisture and heat-associated reactions.

Stored at 21 °C, skimmed-milk powder in hermetically sealed packaging has a shelf life of over a year. Since it contains very little fat, the risk of oxidation is low.

7.3.4 Instantisation

When milk powder is dissolved in water for reconstitution, various processes occur in the powder particles:

  1. Water absorption on the surface (wettability)
  2. Penetration of the water film at the particle surface (penetrability)
  3. Sinking in water (sinkability)
  4. Particle distribution without clumping (dispersibility)
  5. Dissolving of the particles(rate of dissolving)

Milk powder is instantised in order to improve the speed and completeness of powder reconstitution. The methods below successfully improve some of the above sub-processes at the given rate of dissolving of a powder.

 
Abbildung_8_Mikrostruktur_Web
Figure 8: Microstructure of the agglomerated milk powder

Agglomeration
Agglomeration causes the formation of voids between powder particles, allowing rapid and easy penetration of water into these voids during reconstitution (cf. Figure 8). This prevents a viscous layer forming around clusters of compact powder particles, as occurs with non-instantised powders. In non-instantised powders such a viscous layer prevents further water penetration, thereby slowing down reconstitution.

The agglomeration process involves wetting the particle surface with steam, water, or a mixture of both, followed by the actual agglomeration, final drying, cooling, and sifting to remove excessively fine and coarse particles. There are basically two ways of effecting agglomeration:

  • Primary agglomeration is carried out during spray drying by feeding fine powder back into the atomised mist of milk concentrate.
  • Secondary agglomeration is carried out by re-wetting powder which is already dry

Lecithinisation
The type of agglomeration described above is not sufficient for powders containing fat, since free fat on the surface of the powder prevents wetting. These powders are therefore sprayed with a lecithin solution in addition to agglomeration.

7.3.5 Recent findings – various

Increasingly, special milk powders custom-tailored to an intended purpose are being manufactured.  In their production, use is only made of that part of the milk required for a particular application. Thus, there are heavily protein-enriched milk-protein powders, as well as protein-enriched milk powders with an increased casein or whey-protein content (see Chapter 7.4).

Evaporation and drying techniques are optimised not only to improve product quality, but also to reduce energy consumption and overall evaporation and drying costs. Since evaporation enables greater heat recovery than the drying process, and results in lower energy consumption per kg evaporated water, the dry matter is increased as much as possible through evaporation. A constraint arises from the viscosity of e.g. concentrates containing high levels of protein: they must still flow in the evaporator, and be pumpable and sprayable. 

The initial concentration step in skimmed-milk powder manufacture can be carried out by reverse osmosis, allowing concentration to around 25% dry matter. Further concentration is effected by evaporation. Reverse osmosis reduces energy costs.

Because milk-powder plants must produce large volumes of powder in order to operate profitably, various Swiss plants were closed down in the course of structural reorganisation. In 2016 there were around[d1]  7 plants still in operation (Emmi Dagmersellen, Néstle Konolfingen, Hochdorf Swiss Nutrition (Hochdorf and Sulgen), Crémo (Villars-sur-Glâne, Lucens, Thun). Increasingly, plants are specialising and producing ever more special-purpose products, e.g. customised milk-protein powders. Infant formula and nutraceuticals are also important product groups.

7.3.6 Use

Milk powder is a valuable ingredient from both a nutritional and technological/functional point of view, making it popular in a wide range of foods.

Whole-milk powder
Whole-milk powder dissolved in water is used as reconstituted milk. It is a popular and high-quality food, particularly in countries with low milk production. Large volumes of whole-milk powder are used together with cocoa butter, cocoa mass and sugar in the manufacture of milk chocolate. Other confectionery, biscuits, baked goods, sauces and assorted dairy products such as ice cream and processed cheese also contain whole-milk powder.

Skimmed-milk powder
Skimmed-milk powder has numerous applications. It is sold directly to the consumer in the form of reconstituted skimmed milk. Food manufacturers use it in dairy dessert products, ice cream, yoghurt, meat products, vegetarian alternatives to meat, and for coatings, sauces, mayonnaise, instant breakfast drinks and the like.

Powder that is spray-dried via a particularly gentle process from milk whose composition is adjusted before drying to resemble as closely as possible that of human breast milk is used as a basis for infant foods or formula milk.

7.4 Milk-protein powder

Because it is only the properties of individual or a small number of milk components that are required, and because the other components can actually interfere with the desired effect, special powders are increasingly being produced from subcomponents of milk, rather than from all of the milk’s constituents. The rapidly developing membrane separation technologies of microfiltration, ultrafiltration, nanofiltration and reverse osmosis allow the milk to be broken down into its individual constituents.

For protein standardisation in cheese manufacture, for example, products are produced via fine-pored microfiltration in which native micellar casein occurs in high concentrations. The whey proteins are not required for cheese production, so they are separated off and used for other specific purposes. In this separation process, membrane technology makes use of the different sizes of casein micelles and whey proteins. Casein micelles and whey proteins have respective diameters of approx. 0.01–0.3 mm and 0.003– 0. 06 mm. Using the appropriate microfiltration membrane with separation effect in this range, both proteins can be separated. The casein remains in the retentate, and the whey proteins, lactose and minerals pass into the permeate. The additional use of dialysis – the addition of water to dilute the remaining substances – yields casein in a purer form in the retentate. The permeate can be separated from the lactose and minerals via ultrafiltration with an even finer membrane. Here too, the additional use of dialysis can supply the whey protein in a purer form. This two-stage membrane filtration process thus yields caseins and whey proteins in concentrated form. With gentle processing, a large proportion of these proteins remain in their native form with the appropriate functional characteristics, such as the renneting ability of the caseins, or the emulsifying and gelling properties of the whey proteins.

Ultrafiltration is performed only once for the manufacture of total milk-protein powders – if necessary, coupled with dialysis for purification.

After separation and concentration via the membrane separation techniques, the products are preserved by means of spray drying.

7.5 Buttermilk powder

Buttermilk has a similar composition to skimmed milk, but contains slightly more fat as well as milk-fat globule membrane components such as phospholipids and membrane proteins. Table 2 shows the composition of buttermilk powder compared to skimmed-milk powder. Buttermilk powder is made from sweet or sour buttermilk in a similar manner to skimmed-milk powder. Sweet buttermilk powder is preferred for technological/functional applications owing to its greater stability.  Buttermilk powder from sour buttermilk is used almost exclusively for animal nutrition, owing to its susceptibility to oxidation and its resultant instability of taste.

The increased amounts of phospholipids and proteins from the fat-globule membrane in buttermilk impart an increased technological functionality to buttermilk powder, especially powder from ultrafiltered buttermilk. The low-molecular-weight phospholipids are surface-active, and can thus replace conventional emulsifying additives. The membrane proteins also have good emulsifying properties. There are Swiss-manufactured products of this kind on the market.

7.6 Whey powder and whey proteins

Whey is a valuable raw material for producing a wide variety of products. When evaporated and dried without further selective separation, it produces whey powder.

Owing to the low dry-matter content of the whey – approx. 6–6.5% – and the necessary lactose crystallisation, the effort involved in producing whey powder is relatively high.

Since amorphous lactose is sticky and very hygroscopic and would cause problems during drying, the lactose must be crystallised after evaporation and before drying.

The qualities of whey powder are classified according to the degree of lactose crystallisation. This can range between 0 and 95%, and yields caking tendencies of between 0 and 100%.

To crystallise lactose, the whey is concentrated to 42–60% dry matter via evaporation, or via reverse osmosis and evaporation. The concentrate is first cooled to 30 °C and the lactose is crystallised over 4–24 hours. Inoculation with fine lactose crystals sets crystallisation in motion. During crystallisation, the temperature is further reduced to 10 °C. Lactose crystallises as alpha-lactose monohydrate. After crystallisation the concentrate is spray-dried.

Whey concentrate and whey powder are used as ingredients in the food, pharmaceutical and consmetics industries. Whey powder can replace skimmed-milk powder in various products. Whey powder is used in bakery products because it improves the taste of white bread and biscuits. It also ensures a better browning of the crust, and keeps baked goods fresh for longer.  Whey concentrates and whey powder also have certain uses in the beverage industry.

Modern membrane separation technology is dramatically improving opportunities for using whey. Modern processes can overcome the dominance of lactose (72 to 74%) and the high mineral content (8%) limiting the use of whey powder. As described in the ‘milk proteins’ chapter, whey proteins are separated from the other whey components – lactose and minerals – by means of ultrafiltration. Lactose can be obtained from the ultrafiltration permeate through crystallisation and separation. Demineralised whey contains lactose and whey proteins, and is produced as a component of infant food through a combination of nanofiltration, electrodialysis and ion exchange.

7.7 Bibliography

Papers published by Agroscope in the field of concentrates and dried products:

  • Flückiger E, 1981. Ausbeute bei der Herstellung von Dauermilchprodukten. Lebensm.Tech. 14, 18-22.
  • Flückiger E. 1983. Milchbestandteile in der Lebensmittelindustrie. Erfahrungen und Erwartungen. Swiss Food 5, 13-17 (1983).
  • Rüegg M., Moor U., 1993. A standardised approach for the measurement of hygroscopic properties of food materials. Lebensm.Tech. 26, 34-36.
  • Sieber R., 1996. Über die Bedeutung der Milchproteine in der menschlichen Ernährung.. Schweizerische Milchwirt. Forsch. 25, 25-32.
  • Eyer H., 1997. Milchproteine verbessern Lagerstabilität haltbarer Rahmprodukte. Agrarforschung 4, 139-141.
  • Eugster E., Taylor S.E., Puhan Z., Eyer H. 1998. Adsorption behaviour of whey proteins measured by two different methods. Int. Dairy J. 8, 79-81.
  • Eugster-Meier E., 1999. Funktionelle Eigenschaften der Milchproteine. FAM-Inform. 1-37.
  • Eugster-Meier E., 1999. Speiseeis ohne künstlich zugesetzte Emulgatoren!. Impuls 1-2 (1999).
  • Eugster E. 2000. Konzentrierte Buttermilch ersetzt Emulgatoren. Schweizerische Milchzeitung 126, 7-7.
  • Eugster E., Taylor S.E., Puhan Z., 2000. Thermodynamic analysis of the surface activity exhibited by beta-lactoglobulin at the air-water interface. Proc. 2nd Int. Symp. Food Rheology Structure, Zurich, 451-452.
  • Eugster-Meier E., 2001. Adsorptionsverhalten von Proteinen und niedermolekularen Lipiden der Milch an Phasengrenzflächen. ETH Zurich Dissertation No. 14076, 1-125.
  • Bachmann H.P., 2001. Cheese analogues: a review. Int. Dairy J. 11, 505-515.
  • Rehberger, B., Thomet, A., Wyss, B., Bisig, W., 2003. Nanofiltration - Schlüsseltechnologie zur Verwertung von Nebenprodukten. Deutsche Milchwirtschaft. (18), 765-774.
  • Thomet, A., Gallmann, P., 2003. Neue Milchprodukte dank Membrantrenntechnik. FAM-Information 453, 1-42.
  • Thomet, A., Rehberger, B., Wyss, B., Bisig, W., 2004. Gewinnung von Zuckersirup aus Milchserum. Agrarforschung. 11 (8), 348-353.
  • Thomet, A., Bütikofer, U., Rehberger, B., 2005. Herstellung von funktionellen Caseinkonzentraten mit Mikrofiltration. Deutsche Molkerei Zeitung 12, 31-35.
  • Bisig, W., Guggisberg, D., Badertscher, R., Bütikofer, U., Meyer, J., Rehberger, B., 2005.
    Milchproteinpulver und ihre technologischen Eigenschaften: Methodik und Untersuchung.
    ALP science. 488, 1-48.
  • Tahadjodi, S., Marschnig, S., Guggisberg, D., Rehberger, B., Bisig W., 2008. Milchproteine als Emulgatoren. Alimenta (3), 34-35.
  • Bisig, W., Bächtold, U., Guggisberg, D., Caramaschi, A., Rehberger, B., 2009. Optimierung von Milchpulver für die Schokoladen-Herstellung. Deutsche Milchwirtschaft. 60, (1), 2009, 24-26.
  • Schreier K., Schafroth K., Thomet A., 2010. Application of cross-flow microfiltration to semi-hard cheese production from milk retentates. Desalination 250 (3) 1091-1094.
  • Schreier, K., 2010. Elektrodialyse mit bipolaren Membranen. Lebensmittel-Technologie 1/2, 10-11.
  • Bisig W., Hegel C., Schneider M., Guggisberg D., Chollet M. 2011. Natürliche Emulsionen mit Milchingredienzen. 1-1.
  • Guggisberg D., Chollet M., Schreier K., Portmann R., Egger L., 2012. Effects of heat treatment of cream on the physical-chemical properties of model oil-in-buttermilk emulsions.
    International Dairy Journal. (26), 2012, 88-93.
  • Bisig W., 2014. Milchproteine zum Emulgieren. In: MUVA. 3 December, publ.. Ziegmann, B., Kempten. 2014, 1-18. (available on the  Agroscope Website under ‘Publications’).
  • Kopf-Bolanz K., Bisig W., Jungbluth N., Denkel C., 2015. Quantitatives Potenzial zur Verwertung von Molke in Lebensmitteln in der Schweiz.  Agrarforschung Schweiz. 6, (6), 2015, 270-277.
  • Kopf-Bolanz K., Bisig W., Jungbluth N., Denkel C. , 2015. Potentiel quantitatif de valorisation du petitlait dans l’alimentation humaine en Suisse. Recherche Agronomique Suisse. 6, (6), 2015, 270-277.

Additional literature

  • Kopf-Bolanz K., Bisig W., Jungbluth N., Denkel C., 2015. Molke - auf den Teller statt in den Trog. Alimenta. 15, 2015, 28-29.
  • Bisig W., Eugster E., 2010. Membrantrenntechnik, Milchingredienzen und Babynahrung. Teaching module of the School of Agricultural, Forest and Food Sciences HAFL, Agroscope course materials. 68 pages, unpublished.
  • Tamime A.Y., 2009. Dairy Powders and Concentrated Products. Wiley-Blackwell Publishing Ltd. Chichester, United Kingdom; 380 pages.
  • Corredig M., 2009. Dairy-derived ingredients – Food and nutraceutical uses. CRC Press – Woodhead Publishing Limited, Cambridge UK. 690 pages.
  • Kessler H.G., 2002. Food and Bio Process Engineering – Dairy Technology. 5. Revised and expanded edition. Verlag A. Kessler, Munich. 679 pages.