Whey concentrate, isolate, hydrolysate: how do they differ?

Whey protein concentrate, whey protein isolate and whey protein hydrolysate are all made from whey, the liquid left after the curd is separated from milk in cheesemaking. They differ in how far the whey has been processed. Whey protein concentrate (WPC) is whey passed through a membrane filter to remove water, lactose and minerals, leaving a powder of about 35% to 80% protein. Whey protein isolate (WPI) is purified further, by more filtering or by ion exchange, to more than 90% protein. Whey protein hydrolysate (WPH) is whey protein whose chains have also been cut into smaller pieces called peptides, usually with enzymes. The three therefore differ in their manufacturing steps, protein content, remaining lactose and fat, and the size of their proteins.

In short:

• Whey: about 93% water; cow's cheese whey is about 4.5–5% lactose and 0.6–0.8% protein
• Concentrate (WPC): ultrafiltration; about 35–80% protein; US rules allow up to 60% lactose and 1–10% fat
• Isolate (WPI): ultrafiltration with diafiltration, or ion exchange; more than 90% protein
• Hydrolysate (WPH): whey protein cut with enzymes; peptide size depends on the degree of hydrolysis
• Daily amount: the Thai RDI for protein is 50 g, from all foods

This article compares the three by how they are made and what they contain, using a review and laboratory studies. It does not compare them in the body. For how whey compares with casein and plant proteins, see How do whey, casein and plant proteins differ?

What is whey, and what is in it before processing?

Whey is what is left after milk is turned into cheese and the curd is removed. A 2023 study in Membranes by Pires and colleagues, from universities in Portugal, Spain and Turkey, which used ultrafiltration to make kefir products from sheep's and goat's whey, says in its introduction that cheese whey makes up 80% to 90% of the volume of the milk and carries more than half of its nutrients.

The composition of liquid whey

FoodData Central figures are from the US Department of Agriculture (SR Legacy). FoodData Central lists sweet whey and acid whey separately. In both, protein is less than 1 g per 100 g; the Pires study gives lactose as the largest part of cow's cheese whey after water. That is why whey is processed: the aim is to separate the protein from the water and lactose.

Does drying whey raise its protein share?

When whey is simply dried, everything in it is concentrated together, so the share of protein in the solids stays about the same. In FoodData Central, 100 g of dried sweet whey has 12.93 g of protein and 74.46 g of carbohydrate. To raise the share of protein, the other parts have to be removed, which is what membranes and ion exchange do.

How is whey protein concentrate made?

Ultrafiltration

In its introduction, the Pires study says whey protein concentrates, with protein contents between 35% and 80%, are made by ultrafiltration. An ultrafiltration membrane has pores small enough to hold back proteins but let water, lactose and minerals pass through. The part held back (the retentate) becomes the concentrate; the part that passes through (the permeate) carries most of the lactose. In the authors' own ultrafiltration of sheep's and goat's whey, about 95% of the original volume came through as permeate.

What US regulations say

US federal regulations (21 CFR 184.1979c) define whey protein concentrate as whey with enough non-protein parts removed, by physical separation such as precipitation, filtration or dialysis, for the dry product to contain at least 25% protein. On a dry basis, they set:

The rule sets a minimum of 25% protein and a maximum of 60% lactose, so the name covers powders with any protein content from 25% upward.

How is whey protein isolate made?

The introduction of the Pires study says isolates have more than 90% protein and can be made in two ways.

Ultrafiltration with diafiltration

Diafiltration is a further filtering step in which water is added to the proteins held back by the membrane and filtered off again, carrying more of the lactose and minerals with it. The Pires study lists it, together with ultrafiltration, as one of the two routes to an isolate.

Ion-exchange chromatography

In ion exchange, whey proteins are caught on a resin by their electric charge and then released. A 2004 paper by Etzel at the University of Wisconsin describes how bound proteins can be released one by one to make separate protein fractions, or all at once to make a whey protein isolate. In that paper, drinks made with whey protein isolate were clear at pH 2 to 7 before heating, but after heating at 88 °C for 120 seconds only those at pH 3.0 or below stayed clear.

Microfiltration of skim milk

Whey protein can also be taken straight from milk rather than from cheese whey. A 2021 review by France and colleagues at University College Cork explains that microfiltration of skim milk with pores of 0.1 to 0.5 µm, classically at 45 to 55 °C, holds back the casein and gives a whey protein stream of high purity. The authors note that filtration at 20 °C or below is increasingly used, and that the lower temperature changes the protein and mineral make-up of the streams.

What is a whey protein hydrolysate?

A hydrolysate is whey protein, from a concentrate or an isolate, whose long chains have been cut into shorter peptides, usually with enzymes called proteases.

Degree of hydrolysis decides the size

The degree of hydrolysis (DH) is a measure of how far the chains have been cut. A 1994 study from the University of Granada hydrolysed whey proteins with three commercial proteases, two from bacteria and one from an animal source, and measured the size of the peptides. In every case, the range of molecular weights depended only on the degree of hydrolysis reached. At a DH of 20% or more, 65% to 95% of the hydrolysate was made up of peptides smaller than 1,000 Da.

Hydrolysis changes how the protein behaves in food

A 2024 study from the University of Udine in Italy hydrolysed whey protein isolate with two different enzymes. As the degree of hydrolysis rose, surface hydrophobicity and free sulfhydryl groups fell. With one enzyme, foaming was greatest at a DH of 18% to 20% and declined at higher DH; with the other, the hydrolysate kept its ability to form a gel when the DH was below 15%. The authors conclude that the enzyme and the degree of hydrolysis can be chosen to give the properties a food needs.

A Thai study of partial hydrolysis

At Kasetsart University, researchers heated a commercial whey protein concentrate at pH 2.0 and 80 °C for 30 minutes, treated it with the enzyme pepsin at 37 °C for 60 minutes, and spray-dried it with the sugar trehalose. Before spray-drying, the molecular weights of the whey proteins had not changed; after spray-drying, alpha-lactalbumin was the protein broken down the most, while beta-lactoglobulin remained the main protein, alongside peptides smaller than 6.5 kDa. The study (2016) shows that this process cut one whey protein more than another. It was a laboratory study of one concentrate.

Which proteins are in whey, and how big are they?

Whey protein is a mix of several proteins. A 2003 study from the University of Wisconsin–Madison analysed a range of commercial whey protein products and measured the molecular weight of the main proteins.

Main whey proteins (in whey protein isolates)

How concentrates and isolates differed

The same study found that concentrates had major proteins similar to isolates, but more large residual lipid material (small fat globules or phospholipids) and different minor parts, such as lactose and non-protein nitrogen, depending on the product and its protein content. Glycomacropeptide (GMP) was present at very low levels in an isolate made by ion exchange. In the whey protein samples, GMP had a molecular weight of about 8,600 Da.

How do the three compare side by side?

The three are different steps along one process, so a hydrolysate can be made from either a concentrate or an isolate. The figures in the table describe composition and processing only.

How much protein do you need a day?

The Thai Reference Daily Intake (Thai RDI) for protein is 50 g a day, for the general population aged 3 and over, counted from all foods eaten that day. Protein is a source of essential amino acids. For which amino acids the body needs from food, see What are essential amino acids?, and for the Thai reference amounts of other nutrients, see What are the Thai daily reference amounts for each nutrient?

Who should talk to a doctor or pharmacist?

People who react to milk

Whey concentrate, isolate and hydrolysate all come from milk, which the US Food and Drug Administration lists among the major food allergens. Lactose, the natural sugar in milk, is present in different amounts. If you react to milk or a doctor has told you to avoid it, ask a doctor before using any whey product.

If a doctor has told you to limit protein

If a doctor has told you to limit how much protein you eat, follow that advice.

Pregnancy and regular medication

If you are pregnant or breastfeeding, or take medication regularly, talk to a doctor or pharmacist before taking dietary supplements.

Dietary supplements are not intended to prevent, treat or cure any disease.