Consumers are taking a much greater interest in all aspects of health and wellbeing, and are increasingly aware of the importance of a balanced diet, including the essential role that proteins play in the growth, maintenance and repair of every type of tissue in the body.
Milk contains two types of protein, caseins and whey proteins. Whey proteins are digested relatively quickly, and caseins are ideal partners to whey proteins, as they are digested much more slowly. The long casein protein molecules naturally form into stable spherical structures, known as micelles, which coagulate when they hit the acid in our stomachs. It takes our digestive system enzymes much longer to break apart casein molecules and release the individual amino acids. We exploit casein coagulation to make high-protein dairy products such as cheese and strained yoghurts, which represent a key source of nutrition for millions of people around the world.
Think about the differences between whey and caseins in terms of nutrition, and we can see that the two types of milk protein in milk complement each other, providing a continual supply of the amino acid building blocks that our bodies need, both from the easily digested whey proteins, and from the delayed-release casein proteins. But casein also has another nutritional benefit. Unlike whey protein molecules, the casein micelles also bind to calcium and phosphorus, and so are an important source of these key minerals for building strong bones, teeth and muscles. Milk really is a complete food!
Slowly does it
Slow-release caseins are increasingly being used in products that are formulated for people with special nutritional needs, such as the elderly, those who may find it hard to eat – perhaps after illness or injury – and health-conscious consumers and athletes.
It’s also thought that caseins might help to stave off hunger, and some studies have suggested that caseins can help the body to rebuild muscle overnight1,2. Other reported research has found that casein-derived peptides may have antioxidant, antibacterial and potentially blood pressure lowering activity, and stimulate cells of the immune system3,4. And there have been a few pieces of research supporting the case for casein as an aid to weight loss5,6.
Thanks to modern industrial technologies the dairy industry has developed versatile processes for splitting milk into its key constituents, including caseins, whey, fats, lactose and minerals.
By fine-tuning these milk fractionation processes it’s possible to produce casein in different forms, such as acid casein, rennet casein, caseinates, and micellar casein concentrates and isolates, which all contain varying levels of other milk components such as lactose and minerals. Traditional methods for making casein-rich dairy foods such as cheese and strained yoghurt are based on adding acid, enzymes such as rennet, or bacteria to the milk, and collecting the solid casein curds that separate out7.
As well as representing a key protein for nutritional products, casein extracted from milk is used to improve the taste and textures of the wealth of foods and food ingredients. Caseins may be used as ingredients in non-dairy (lactose-free) coffee and tea whiteners, dressings, sauces and spreads, as well as in cheese and ice cream products. Acid-and rennet-based methods are also used to extract caseins that are used for other applications, including emulsifiers and binders for plastics and fibres, paints and textiles, and even cosmetics and personal care products.
Making micellar casein
During the last couple of decades, industry has been turning to microfiltration techniques that can extract casein in its native, micellar form, without the use of acids or enzymes. Micellar casein extracted using microfiltration is heat stable, and has a much milder flavor and texture, so it is ideal as a high-quality component for nutritional formulas, powders and health drinks and snacks, as well as for its more traditional use in cheese making.
The microfiltration process essentially forces the milk, under pressure, through semipermeable membranes. The whey proteins, lactose and minerals are small enough to pass through the membrane, and so varying amounts of these components can be removed in the fraction called the permeate. Casein molecules are larger than the whey proteins, and can’t pass through the membrane, so they are retained, along with some other milk components, in the retentate. This then undergoes evaporation to remove water, before spray drying and packaging. By carefully configuring the microfiltration membranes, filtration conditions, and subsequent stages of processing, it is possible to precisely control the retentate and final casein composition, including how much lactose, or calcium, remain. And of course, the whey that is filtered out can be used for a wide range of nutritional product streams. Importantly, the whey is not exposed to the cheese-making process, but is a valuable key product from microfiltration, and is a key component in a range of nutritional products.
GEA partnerships for sustainable processes
Here at GEA we understand the urgent global need to meet the protein requirements of different populations, and so we have developed versatile solutions through test work for casein recovery that can be configured precisely to match industry and market demands and expectations.
Our GEA scientists, engineers and industry specialists partner with global customers in the dairy industry to configure efficient, environmentally sustainable plants for processing the highest quality casein products using acid, rennet and microfiltration methods. Our expertise spans complete plants for casein recovery, from liquid processing, through to evaporation, spray-drying and packaging. We also offer microfiltration technologies based on long-life ceramic membranes, and cost-effective polymeric membranes that offer different approaches to recovering and optimizing micellar casein.
“Using GEA membrane technology we are helping customers to make better and more specialized products,” commented Ole Lillevang, technology specialist at GEA Membrane Technology Group. “We can target product specifications (compositions and specific characteristics) through the use of various membrane technologies such as ceramic or polymeric membrane filtration, depending on the exact end goals.”
“Our slogan is ‘Engineering for a better world,’ and that’s what we always strive for, added Preben Kønigsfeldt, sales team lead for GEA Membrane Technology Group. “We focus on using our expertise to develop the technologies that will support industry manufacture of innovative recipes, and safe and healthy products for populations all around the world, whatever their dietary needs.”