Is milk a good source of protein?

In 1886, a German chemist proposed a method for pasteurising milk intended for consumption by children. The development of this method had a significant impact on the processing and safety of milk available for sale. Nowadays, it is one of the staple dairy products in our daily diet. Its value stems, amongst other things, from its protein and mineral content, but also from its numerous culinary and technological uses.

1. Milk production
2. Protein in dairy products
3. Milk in the kitchen
4. FAQ

Milk production

Collection and cooling

Milk intended for sale is collected from dairy farms using closed milking systems and is then rapidly cooled to limit the growth of microorganisms. Transport tanks and tankers maintain a low temperature during transport to the dairy. Each batch is tested for, amongst other things, its composition, microbial count, the presence of antibiotic residues and other characteristics determining whether the raw milk is accepted.

Filtering and homogenisation

At the plant, the milk is filtered or centrifuged, after which some of the fat is separated off. The skimmed milk and cream are then combined in the appropriate proportions to produce a product with a specific fat content, for example 0.5%, 1.5%, 2% or 3.2%. Homogenisation – the process of ensuring a uniform consistency throughout the entire volume – breaks down the fat globules under high pressure, preventing the cream from rising to the surface and ensuring a consistent texture.

Pasteurisation

Pasteurised milk is usually heated for a dozen or so seconds at a temperature of around 72–75°C, then rapidly cooled, and must be stored in the fridge. UHT milk, or ultra-high-temperature pasteurised milk, is heated to around 135–150°C for a few seconds and filled into sterile containers; it can therefore be stored outside the fridge before opening.

Protein in dairy products

Cow’s milk consists of approximately 87 per cent water. 100 ml usually contains 3.2–3.5 g of protein, around 4.7–5 g of lactose and a fat content depending on the specific product variant. Around 80 per cent of milk proteins are caseins, and around 20 per cent are whey proteins. Both fractions provide all the essential amino acids and are highly digestible.

A 250 ml glass usually provides 8–9 g of protein. Natural yoghurt and kefir generally contain around 3–5 g of protein per 100 g, Greek-style yoghurt and skyr around 8–12 g, cottage cheese around 11–13 g, and quark around 17–20 g. In mature cheeses, the protein content is often 24–30 g per 100 g, but these products are also a more concentrated source of fat, energy and salt. The differences stem mainly from the removal of water and whey during production. Whey protein supplements are the most concentrated. Concentrates usually provide around 70–80 g of protein per 100 g of powder, whilst isolates provide around 85–90 g. A standard 30 g serving of a protein supplement typically contains around 20–27 g of protein, depending on the product’s composition.

Milk can therefore be considered a source of good-quality protein, as it contains all the essential amino acids and is highly digestible. However, it is not a highly concentrated source.

Estimated protein content in various dairy products

Milk in the kitchen

Milk has a wide range of culinary uses in both sweet and savoury dishes. It is used as a base for porridge, gruel, custards, milkshakes, hot chocolate and milk-based desserts. It is also an ingredient in pancakes, waffles, cakes, sweet buns and creams, where it affects the texture, moisture content and flavour of the finished product. In savoury cooking, it is added to cream soups, sauces, béchamel, mashed potato, casseroles and flour-based dishes. It can temper the intensity of spices and give dishes a creamier texture.

When heating, it is important to monitor the temperature, as it can easily boil over or burn at the bottom of the pan. In recipes requiring a thicker consistency, condensed milk or powdered milk can be used. For frothing, milk containing at least around 3.2 g of protein per 100 ml works best. The 1.5–2% fat variety usually produces a more stable froth, whilst 3.2% milk creates a creamier, though slightly less voluminous, froth.

“Milk is a source of complete protein, as it provides all the essential amino acids and is highly digestible. However, it does not contain as much protein as more concentrated products, such as skyr, quark or protein supplements. It is therefore best to treat it as one component of your daily diet, rather than your main source of protein.” Łukasz Domeracki – Dietitian

FAQ

Is milk a good source of protein?

Yes. Milk provides high-quality protein containing all the essential amino acids. However, it is not a product with a very high protein concentration – 100 ml usually contains around 3.2–3.5 g.

How much protein is there in a glass of milk?

A glass of milk (250 ml) provides on average around 8–9 g of protein, regardless of its fat content.

Is milk a better source of protein than yoghurt?

It depends on the type of yoghurt. Natural yoghurt contains a similar amount of protein to milk, whilst skyr and Greek yoghurt usually provide significantly more.

Does the fat content affect the amount of protein in milk?

Slightly. Milk with 0.5%, 1.5%, 2% and 3.2% fat contains a similar amount of protein. It differs mainly in its fat content and energy value.

Does pasteurisation destroy the protein in milk?

No. Heat treatment may cause slight changes to the structure of some proteins, but milk remains a source of complete, highly digestible protein.

Which has more protein – milk or a protein supplement?

Protein supplements are a much more concentrated source of protein. A 30 g serving of whey protein concentrate or isolate usually provides around 20–27 g of protein, whilst a glass of milk provides around 8–9 g.

Is milk a good choice after a workout?

Milk can be one component of a post-workout meal, as it provides high-quality protein and carbohydrates in the form of lactose. However, the final choice depends on your overall daily diet and individual protein requirements.

Who should avoid drinking milk?

Milk may not be a suitable choice for people with an allergy to cow’s milk proteins. On the other hand, people with lactose intolerance can often opt for lactose-free milk, which retains a similar nutritional value.

Sources:

• van Lieshout, G. A. A., Lambers, T. T., Bragt, M. C. E., & Hettinga, K. A. (2020). How processing may affect milk protein digestion and overall physiological outcomes: A systematic review. Critical reviews in food science and nutrition, 60(14), 2422–2445. https://doi.org/10.1080/10408398.2019.1646703
• Rutherfurd, S. M., Fanning, A. C., Miller, B. J., & Moughan, P. J. (2015). Protein digestibility-corrected amino acid scores and digestible indispensable amino acid scores differentially describe protein quality in growing male rats. The Journal of nutrition, 145(2), 372–379. https://doi.org/10.3945/jn.114.195438
• A Castro, L. H., S de Araújo, F. H., M Olimpio, M. Y., B de B Primo, R., T Pereira, T., F Lopes, L. A., B S de M Trindade, E., Fernandes, R., & A Oesterreich, S. (2019). Comparative Meta-Analysis of the Effect of Concentrated, Hydrolyzed, and Isolated Whey Protein Supplementation on Body Composition of Physical Activity Practitioners. Nutrients, 11(9), 2047. https://doi.org/10.3390/nu11092047