What is whey in naturally and where does it come from?

December 31, 2025 •

3 min read

Approximately 20% of cow's milk is whey, and 80% is casein, both being complete, high-quality proteins. Naturally, whey is a liquid separated during cheese and yogurt making. This clear liquid is packed with nutrients like proteins, vitamins, and minerals.

Quick Summary

This article explores the origin of natural whey, a nutritious liquid byproduct of dairy processing. The content describes how whey separates during cheesemaking and yogurt production, its distinct composition compared to casein, and its presence in various natural food products.

Key Points

Origin: Naturally, whey is the liquid part of milk that separates from solid curds during cheesemaking and yogurt-making.
Nutrient-Rich: This liquid is rich in water-soluble proteins, lactose, vitamins, and minerals.
Dairy Distinction: The two main proteins in milk are whey (20%) and casein (80%), with whey being rapidly absorbed and casein digested slowly.
Food Sources: Natural liquid whey is found in yogurt, cottage cheese, and ricotta cheese.
Homemade Uses: Leftover liquid whey from yogurt or cheese can be used in baking, smoothies, or as garden fertilizer.
Not a Waste Product: Once considered a waste product, whey's nutritional value has led to its modern processing into powdered supplements.

The True Source of Whey: Milk to Curds and Whey

Whey's natural origin begins on a dairy farm. Whey is a liquid separated from milk solids, curds, during cheesemaking or yogurt production. This separation is a natural process, often accelerated by rennet or edible acids like lemon juice.

During cheesemaking, milk is heated and a coagulant added, causing casein proteins to clump and form curds. The remaining liquid is whey. The whey type depends on the coagulant. Sweet whey comes from rennet-coagulated cheeses like cheddar, while acid whey results from acidic dairy products like Greek yogurt.

This byproduct was once considered waste, but its high nutritional value is recognized and repurposed. Processing technology allows filtration and drying of this liquid into concentrated powder forms, but its fundamental nature remains a natural part of dairy production.

The Composition and Types of Natural Whey

Whey is a complex mix of water-soluble proteins, including β-lactoglobulin, α-lactalbumin, and immunoglobulins. It also contains lactose, water-soluble vitamins (especially B-group vitamins), and minerals like calcium and potassium.

Common Forms and Their Natural Origins

Sweet Whey: Produced during hard cheese making, this whey has a higher pH and is slightly sweeter. It is a source for ricotta cheese.
Acid Whey: A byproduct of soft cheeses and strained yogurt, this whey has a lower pH and a tangier flavor. It is often used in baking or as a soil amendment.
Native Whey: Unlike traditional whey from cheese production, native whey is extracted directly from skim milk using low-temperature physical processes. It is not a byproduct but a primary protein isolated from milk, often retaining a higher biological value and a slightly different amino acid profile.

Where to Find Whey in Naturally Occurring Foods

Whey can be found naturally in several food items, though often in liquid or unprocessed states. Incorporating these into your diet offers benefits without processed products.

Yogurt: The liquid that sometimes collects on top of yogurt is naturally occurring whey. Stir it back in for extra nutrients and a creamy texture.
Cottage Cheese: Cottage cheese is primarily casein curds, but it is packed in a milky liquid rich in whey. This makes cottage cheese a good source of both slow-digesting casein and fast-digesting whey protein.
Ricotta Cheese: This cheese is made by reheating the liquid whey leftover from other cheeses. It's a true whey-based food product that is rich and creamy.
Kefir: As milk kefir cultures and strains, it separates into curds and whey. The remaining liquid is kefir whey, which can be used in other fermented recipes or baking.

The Difference: Casein vs. Whey in Naturally

Casein and whey are two protein fractions with different properties. Understanding these differences is key to appreciating whey.

Comparison Table: Casein vs. Whey Naturally in Milk


Feature	Casein (Curds)	Whey (Liquid)
Natural Form	Solid curds during coagulation	Liquid, clear or pale yellow fluid
Percentage in Milk	Approx. 80% of milk protein	Approx. 20% of milk protein
Digestion Rate	Slow-digesting, forms clots in stomach	Rapid-digesting, absorbed quickly
Common Natural Foods	Cottage cheese, cheese	Yogurt liquid, ricotta, kefir whey
Key Amino Acids	Higher in glutamine, methionine	Higher in BCAAs, especially leucine
Effect in Body	Sustained release of nutrients for long periods	Quick boost of amino acids for muscle repair

Natural Uses of Liquid Whey

Liquid whey from cheesemaking was a valuable resource. Large-scale processors dry it for powder, but at home, the liquid can be used. It can be a base for smoothies and shakes, incorporated into bread doughs and pancake batters for moisture and nutrients, or added to soups and stocks for a richer flavor. Some gardeners use acid whey, diluted with water, to fertilize plants that thrive in acidic soil, such as tomatoes.

Conclusion: Appreciating Natural Whey

Whey in naturally is the liquid part of milk that separates from the curds. It is a complete, high-quality protein containing all essential amino acids, along with vitamins and minerals. This dairy byproduct is a powerhouse of nutrition. Recognizing its natural forms allows a holistic understanding of this versatile and beneficial milk component. The journey of whey from a simple liquid in dairy to a popular supplement is a testament to its nutritional value, but its natural origins define it. You can learn more about whey protein's production and benefits from credible sources like the U.S. Dairy industry.

Frequently Asked Questions

Yes, whey is a natural component of milk, representing about 20% of its total protein content. It is inherently present in its liquid form before any processing, such as cheesemaking, separates it from casein.

Yes, the clear liquid that pools on top of yogurt is naturally occurring whey. It contains many of the vitamins, minerals, and proteins found in milk and should be stirred back in, not discarded.

Whey protein powder is a processed concentrate of naturally occurring liquid whey. While derived from a natural source (milk), it undergoes factory processing like filtration and drying to become a powder. Some are more minimally processed than others.

Sweet whey is produced when milk is coagulated with rennet to make hard cheeses like cheddar, resulting in a higher pH. Acid whey is the byproduct of using an acid to curdle milk for products like strained yogurt.

Yes, you can make whey at home by straining yogurt or by making simple soft cheese like ricotta. When straining yogurt, the liquid that drains off is acid whey. If making ricotta from cheesemaking leftovers, you are using sweet whey.

Native whey protein is extracted directly from skim milk, rather than as a byproduct of cheese production. This process is typically done at lower temperatures using membrane filtration to preserve more of its natural structure.

The main difference is their digestion rate. Whey is a 'fast' protein that is absorbed quickly, while casein is a 'slow' protein that forms a gel in the stomach and provides a sustained release of amino acids.