What is whey protein made out of?

October 17, 2025 •

3 min read

Over a billion pounds of cheese are produced in the United States every year, with the whey protein being a valuable byproduct. But many people are still unaware that whey protein, a popular dietary supplement for athletes and health enthusiasts, is fundamentally a dairy product derived from cow's milk during the cheese-making process.

Quick Summary

Whey protein is derived from milk as a byproduct of cheese production. During cheesemaking, milk is curdled, separating into solid curds (casein) and liquid whey. This liquid whey is then filtered and dried to create the powdered supplement, which comes in various forms depending on its level of processing.

Key Points

Milk is the primary source: All whey protein originates from milk, with cow's milk being the most common source.
Cheesemaking byproduct: Whey is the liquid byproduct left over after milk is coagulated and the solid curds (casein) are removed to make cheese.
Filtration refines the protein: The liquid whey is processed using filtration techniques like microfiltration and ultrafiltration to separate the protein from fats, lactose, and water.
Drying creates the powder: After filtration, the concentrated whey liquid is dried into a fine powder, preserving its nutritional value.
Different types exist: The level of processing determines the final product, leading to different forms such as whey concentrate, isolate, and hydrolysate.
Bioactive compounds are retained: Depending on the processing method, whey protein can contain a variety of beneficial bioactive compounds, including immunoglobulins and lactoferrin.

From Milk to Powder: The Journey of Whey Protein

The Milking and Pasteurization Process

The journey of whey protein begins on a dairy farm. Fresh milk from cows is collected and transported to a processing facility in refrigerated tanks to prevent bacterial growth. Upon arrival, the milk undergoes pasteurization, a heating process (around 70-80°C) designed to kill any remaining harmful bacteria, ensuring the milk is safe for consumption. After heating, the milk is quickly cooled back down to around 4°C, a process that ensures sanitation without compromising the milk's nutritional profile. This carefully managed process sets the stage for the crucial next steps in creating whey protein.

The Role of Cheesemaking: Separating Curds and Whey

The creation of whey is intrinsically linked to cheesemaking. After pasteurization, the milk is heated again and specific enzymes or an edible acid (like citric acid) are added to it. These additives cause the milk to curdle, separating the milk's two primary proteins: casein and whey.

Curds: The solid, semi-solid part of the milk, primarily made of casein protein, which is used to make cheese.
Whey: The watery, yellowish liquid left behind after the curds have been strained. Historically, this liquid whey was often discarded, but processors eventually discovered its high nutritional value, particularly its rich protein content. This realization transformed whey from a waste product into a highly sought-after ingredient for a variety of health and food products.

Refining the Whey: The Filtration Process

Once separated from the curds, the liquid whey contains not only protein but also other components like lactose, fats, minerals, and water. To isolate and concentrate the protein, manufacturers use a series of filtration techniques. The most common method is membrane filtration, which uses a system of specialized filters to remove different components based on their size.

Microfiltration (MF): In this initial filtration step, liquid whey passes through microfilters to block larger particles, including bacteria and remaining fat globules.
Ultrafiltration (UF): Following microfiltration, the liquid undergoes ultrafiltration, a process that retains the large protein molecules while allowing smaller molecules like lactose, water, and some minerals to pass through. The concentrated protein liquid that remains is then used to create whey protein concentrate (WPC).
Ion Exchange : An alternative, more aggressive method of purification that chemically separates the whey proteins from other components. This process can yield a higher protein percentage but may also denature, or damage, some of the proteins.

Drying and Flavoring: Creating the Final Product

After the whey has been concentrated through filtration, it is ready to be transformed into a powder. This final step involves spray-drying, a process where the concentrated liquid is sprayed into a chamber of hot air. The hot air evaporates the remaining water almost instantly, leaving behind a fine, dry powder. This drying process is crucial for preserving the nutritional integrity of the protein.

Finally, the resulting unflavored whey powder is tested for quality and can then be combined with other ingredients. Many commercial whey products include emulsifiers (like sunflower lecithin to help it mix well), flavorings, and sweeteners to improve taste and texture. The product is then packaged and distributed to consumers.

Comparison Table: Whey Concentrate vs. Isolate


Feature	Whey Protein Concentrate (WPC)	Whey Protein Isolate (WPI)
Processing	Microfiltration and Ultrafiltration	Additional processing to remove more fat and lactose
Protein Content	70-80% protein by dry weight	Over 90% protein by dry weight
Lactose	Contains some lactose; can cause issues for the lactose-intolerant	Contains very little or almost no lactose
Fat	Contains small amounts of fat	Most fat is removed during processing
Cost	Generally more affordable	Typically more expensive due to extra processing
Bioactive Compounds	Retains more immunoglobulins and lactoferrin	Lower levels due to intensive processing

Conclusion

In summary, the next time you scoop whey protein into your shaker, you'll know that its origins trace back to the dairy industry, specifically the age-old process of cheesemaking. What was once considered a dairy waste product is now a nutritional powerhouse, carefully refined through a multi-stage process of separation, filtration, and drying. This journey from milk to powder is a testament to the efficient ingenuity of modern food production, providing a high-quality, convenient protein source for millions. Understanding what is whey protein made out of not only gives you insight into your supplement but also a deeper appreciation for the complex process that brings it to your table.

Related Information

For more technical details on the various processing techniques, including microfiltration and ultrafiltration, you can refer to the Tetra Pak Dairy Processing Handbook.

Frequently Asked Questions

The base ingredient for whey protein is cow's milk. The protein is isolated from the watery, liquid portion of milk that separates from the solid curds during the cheesemaking process.

Most commercial whey protein is a byproduct of cheese production. However, 'native' whey protein, a less common and more expensive variety, can be extracted directly from skim milk without going through the cheesemaking process.

No, whey protein is a dairy product because it is derived from milk. While whey protein isolate has most of the lactose removed, it is still not considered dairy-free.

The key steps involve collecting and pasteurizing milk, adding enzymes or acid to separate the liquid whey from solid curds, using filtration to concentrate the protein and remove impurities, and finally, spray-drying the concentrated liquid into a powder.

Whey protein isolate is more expensive than concentrate because it undergoes additional, more intensive processing, such as further microfiltration, to remove more fat and lactose, resulting in a purer product with a higher protein percentage.

The main protein components in whey are Beta-lactoglobulin, Alpha-lactalbumin, Bovine Serum Albumin, and Immunoglobulins.

Yes, whey protein is a complete protein source, meaning it contains all nine essential amino acids that the human body cannot produce on its own.