Milk – a complex product
Milk is 87 percent water. But it is the other 13 percent of ingredients that interests food developers: milk sugar (lactose), milk fat, milk protein and minerals. Each of these ingredients includes several components in turn, producing a range of different “capabilities”. As new foods or production processes are developed, the technical properties of individual milk components can be used to fulfil specific requirements.

Let’s scratch the sur­face first be­fore we look in more de­tail. As a milk proces­sor fo­cussing on “pow­der pro­duc­tion” as our core area of ex­per­tise, we are more in­ter­ested in the lac­tose, milk fat, milk pro­tein and min­eral com­po­nents of milk than the 87 per­cent water (see di­a­gram of milk and its com­po­nents). Every in­gre­di­ent has spe­cific prop­er­ties of in­ter­est to the food pro­cess­ing in­dus­try. These prop­er­ties vary de­pend­ing on how the com­po­nents are ex­tracted and (sub­se­quently) dried. This re­sults in al­most in­nu­mer­able ways to use the raw ma­te­r­ial of milk – even be­fore we con­sider any fur­ther sep­a­ra­tion of the four com­po­nent in­gre­di­ents.

Step one: stan­dar­d­is­ing the un­pas­teurised milk

Com­plex tech­ni­cal pro­ce­dures are re­quired to sep­a­rate the milk com­po­nents. The old­est and best-known tech­nique is sep­a­rat­ing the milk fat, which in­volves di­vid­ing the milk into milk fat (cream) and skimmed milk. This step is still car­ried out by all milk proces­sors today to stan­dard­ise the spe­cific fat con­tent of un­pas­teurised milk. After con­cen­tra­tion, this stan­dard­ised milk can be dried and sold as milk pow­der. For whole milk pow­der, milk fat is added back to the skimmed milk to the de­sired fat value. This stan­dard­ised whole milk is then con­cen­trated and dried. For the choco­late in­dus­try, whole milk con­cen­trate is then roller dried (see the ar­ti­cle “HOCHDORF – mak­ing choco­late his­tory” on our web­site for more in­for­ma­tion on this process).

Step two: fil­ter­ing the pro­tein com­po­nents

The next step in the milk crack­ing process that splits milk into its com­po­nents is the frac­tion­a­tion of the pro­teins. Milk con­tains two main pro­tein groups: ­caseins and whey pro­teins. The ca­seins make up around 80 per cent (ap­prox. 27 grams) of the av­er­age 34 grams of pro­tein in every kilo­gram of milk. Ca­seins are re­tained in milk for cheese pro­duc­tion. The sec­ond pro­tein group is con­tained in the whey and known as whey pro­teins.

“Com­plex tech­ni­cal pro­ce­dures are re­quired to sep­a­rate the milk com­po­nents.”

The HOCHDORF Group uses mem­brane tech­nol­ogy (ul­tra­fil­tra­tion, mi­cro­fil­tra­tion) for pro­tein frac­tion­a­tion. This tech­nol­ogy re­tains the milk pro­teins (re­ten­tate) using mem­branes while the lac­tose and min­er­als pass through the fil­ter (per­me­ate). By vary­ing the raw ma­te­ri­als and types of mem­branes, we pro­duce a wide port­fo­lio of spe­cial­ist pro­tein con­cen­trates: milk pro­tein con­cen­trate with 85% pro­tein (MPC85), con­cen­trate with an in­creased pro­por­tion of ca­sein (mi­cel­lar ca­sein), whey pro­tein con­cen­trates (WPC60, WPC80) and but­ter­milk pro­tein con­cen­trate (BM60). The pro­tein con­cen­trates are mostly sold in pow­der form; liq­uid pro­tein con­cen­trate needs to be cooled.

How­ever, split­ting milk pro­tein into ca­sein and whey pro­tein is by no means the end of the story. De­pend­ing on the cus­tomer re­quire­ments and ap­pli­ca­tion, we can use fur­ther pro­cess­ing steps (such as heat­ing) to op­ti­mise spe­cific fea­tures. In ad­di­tion, the trend is to­wards a fur­ther sep­a­ra­tion of the two main types of milk pro­tein.

Milk and its components

Technical properties

Why invest so much effort in milk cracking? The answer is simple: depending on the fractionation and processing, milk proteins have interesting technical properties (see Figure “Technical properties of milk proteins). In terms of food law, they are classed as ingredients rather than additives, so milk proteins do not appear as E-numbers on product declarations. Ready availability also makes them popular in the food industry.


Milk proteins in the food industry

The diverse technical properties of milk proteins mean they can be used in a wide variety of applications. Cheese dairies enrich their milk with milk proteins or micellar casein, for example, to increase the cheese yield. Whey proteins have an extremely high nutritional value; the amino acid composition is perfect, so they are an important ingredient in infant formula. The emulsifying and hydrophilic properties of whey proteins make them highly suited to the production of convenience foods, ice cream or drinks.

“Milk proteins have interesting technical properties that vary according to their fractionation and processing.”

Whey protein concentrates with no fat are used in fine sorbets, cakes and cookies, recognised for their foam-forming properties. Buttermilk, a by-product of butter production, also contains a high proportion of phospholipids (fat) in addition to protein. Proteins and fats are both concentrated in the buttermilk protein concentrate, giving the product extremely good emulsifying properties. Buttermilk protein can be used as an alternative to egg yolk in products such as ice cream.

Intensive collaboration with customers

The market – and more specifically customer wishes – determine the product requirements and the further development of milk fractionation today. In the beginning, however, it was the other way round: technicians were interested in how milk could be split into individual components. In terms of protein fractionation, the impact of advances in technology in the early stages should not be underestimated. It suddenly became possible to concentrate whey proteins – but there was no market for them. So this (application) research was also driven forward at the beginning. Advising customers on technical aspects is still important for protein sales today. Our developers work with customers intensively on each individual project to pinpoint the right protein concentrate for the desired formulation. We will be happy to help you with any questions.

Marc Vissers at thenanofiltration unit

An employee at the nanofiltration unit in the Sulgen plant.

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