Protein extraction methods
Membrane filtration is essentially using a sieve with specific hole sizes to concentrate proteins and remove unwanted components from the whey. There are 3 main types of membrane filtration – microfiltration (MF), ultrafiltration (UF) and cross-flow membrane filtration (CFM). The type of filtration/ combination of filtration methods will determine the concentration of proteins and other nutrients in the final product.
Microfiltration (MF) – Microfiltration passes raw whey over a porous membrane at low pressure and low temperatures. The pore sizes are between 1.4um and 0.1um in diameter and they allow minerals, carbohydrates (including lactose) and whey proteins to pass through. Caseins and fats can also pass through if larger diameters are used, and this will increase the nutritional value of the whey powder but reduce protein content. All material which passes through the membrane is then collected and dried1. This process can yield a whey protein powder with around 80% protein, which will contain fats, carbohydrates, minerals and other nutrients. Whey protein produced my microfiltration is often called a whey protein concentrate (see below for more details on concentrates and isolates).
Ultrafiltration (UF) – Ultrafiltration passes raw whey over a porous membrane at medium pressure and low temperatures. It uses a much smaller pore size than microfiltration which only allows carbohydrates (such as lactose) and most minerals to pass through. Everything which doesn’t pass through is collected and dried1. When combined with micro-filtration this can create a protein powder which contains more than 90% protein and very little fats, carbohydrates and other nutrients2. Whey protein produced by a combination of microfiltration and ultrafiltration can be called whey protein isolate or concentrate depending on the protein concentration of the final product. .
Cross-flow membrane filtration (CFM) – Cross flow membrane filtration (sometimes called tangential flow filtration) is a more efficient type of microfiltration. The same temperature and pore sizes can be used as conventional microfiltration, but rather than forcing the raw whey into a mesh, the raw whey passes over a porous membrane at varying pressures several times (see diagram)7.
As CFM is more efficient that regular microfiltration, it can yield a protein content of 90%+, and so whey produced by CFM is often called a whey isolate.
For ion exchange filtration, raw or micro-filtered whey is passed through a column which binds to proteins. Proteins stick to the column and everything else (carbohydrates, fats, vitamins etc) pass through. Then by changing the pH with different acids and bases, the proteins are released from the tube and collected3. Ion exchange is extremely efficient at concentrating protein and can get concentrations between 90%-96%, but will contain very little of any other nutrients.
Ion exchange produces the highest concentration of proteins of all methods, and is called an isolate, but because of the pH used in this extraction method many types of proteins will denature.
Proteins are complex structures (see image to the right) and are held in their complex position by chemical bonds at specific points. When you heat or change the pH of the protein, some of these bonds break and new ones may form. This causes the shape of the protein to change, and this is what is meant by a denatured protein. It is still a protein in the sense in is made out of amino acids, but it can no longer fulfil whatever role it was designed to do. This is important in whey for 2 reasons.
The first is that whey protein contains some proteins which actively support your health. To name a few: lactoferrin, α-lactalbumin, β-lactoglobulin, IgG1, IgG2, IgM, and IgA4. All these proteins support your immune system and your overall health, but if they get denatured, they don’t.
The second reason is that some denatured proteins are more difficult to digest than undenatured. There are exceptions to this (such as egg protein), but in most cases denatured proteins are more difficult to digest8. This doesn’t mean you don’t ever digest them, you do, but it just takes more time.
So ideally you would want as much of the protein undenatured as you can to get the nutritional benefits of the proteins and to absorb them quickly, but denatured proteins still do get absorbed and count towards your total protein.
Temperature is important in all food processing because heat causes many nutrients (including proteins) to break down/ denature. With this in mind, it is no surprise to see claims like ‘low temperature processing’ on the label of many whey proteins. Filtration and concentration is usually done at low temperatures, so there is very little risk of denaturing proteins here. However temperatures as high as 120oC can be used in the drying/ powdering stages (sometimes called instantiating), so having low temperatures here is important. Manufacturers don’t publicly state the temperature they use here, so you will have to ask them for specifics, but here is a table to reference the information you find:
|Temperature||Amount of protein denatured|
If a company claims that all of their processing is done at a low temperature to avoid denaturing proteins, then you shouldn’t have to worry about proteins denaturing, but it never hurts to ask.
Whey concentrates VS isolates
Whey protein isolates (WPI) – High in protein (90%+) and low in fats, carbohydrates, minerals. Isolates made by ion exchange will contain denatured proteins so you won’t get the immune supporting benefits from these proteins, whereas the proteins produced by CFM should not be denatured. Isolates can be thought of as a pure source of protein.
Whey protein concentrates (WPC) – Lower in protein (usually 70%-90%) and contain significant amount of fats, vitamins, minerals and carbohydrates (although some of these can be filtered out). The fats in whey concentrates often contain reasonable amounts of beneficial fats such as CLA and much of the immune supporting proteins will be remain active. This makes whey concentrates more nutritious and ‘like a food’ than isolates.
Hydrolysed whey is whey protein which has been partially digested by enzymes, often at high temperatures, and sometimes in the presence of acids. Proteins are made of extremely long chains of amino acids all bonded together, and in order to absorb the protein the digestive system needs to break most of these bonds. The process of breaking these bonds is called hydrolysis, and so the proteins in hydrolysed whey are partially broken down to make digestion easier and quicker. Breaking proteins down like this would mean that none of the beneficial proteins will be present in the powder, and both whey concentrates and whey isolates can be hydrolysed.
Whilst it makes sense in theory that hydrolysed whey is digested faster than normal whey, this isn’t backed by consistent research. This may be because whey proteins are rapidly broken down and absorbed already, and so partially digesting the whey makes very little difference. At any rate, there are several studies which have shown that there is no significant difference between standard whey protein and hydrolysed whey protein absorption9.
However, casein proteins (which are very slow absorbing proteins also extracted from milk) do seem to benefit from undergoing hydrolysis, and are absorbed 25%-50% faster than intact casein proteins10.
Understanding protein content
‘As is’ vs ‘dry weight’ – ‘As is’ is the amount of protein you get per serving from the bag/ tub as you receive it. ‘Dry weight’ is the amount of protein you would get if you dried the powder in an oven to remove every little bit of water, and then took the recommended serving size. They differ because despite the protein being in a dry powder form, there is still some water content in the powder. The figure you want to look at is the ‘as is’, because this is the amount you will actually get per serving. A perfect example of this is this protein powder called Pure 80 by Bodybuilding Warehouse. The name strongly implies that it contains 80% protein, which is pretty standard for a whey protein concentrate, and what you would expect. However, if you look at the ‘Nutrition Info’ tab you will see that the protein content ‘as is’ is 76%, whereas the ‘dry weight’ protein content is 80%. Despite its name and description, this protein powder doesn’t actually contain 80% protein. You can easily use this percentage calculator to find out the accurate amount of protein in a powder based on the ‘as is’ protein value.
The variation between ‘dry weight’ and ‘as is’ can be about 5%, which is often enough to tip the scales in favour of another brand, particularly if they are similar in all other aspects. Many companies don’t publish both values on the label/ website, so you often don’t know which one they quote. You’d like to think that brands would go with the ‘as is’ value, because that is the accurate one, but I have seen some companies quote their protein percentage based of their dry weight value, so be warned!
Flavours – Some companies quote the unflavoured protein values in the product description for all the flavour variations. This is not accurate, and some flavour combinations can reduce the protein content by as much as 15%, which means when you expect 25g of protein per serving you are actually getting 21.25g. Keep an eye on the nutritional values the company quotes, and see if they vary from flavour to flavour. If they don’t, you can be sure they are quoting the unflavoured amount, and the actual protein concentration will be lower.
This one is pretty self explanatory – the whey is made from the milk of cows which have enjoyed their natural diet. The importance of this is that whey from grass-fed cows is higher in all kinds of beneficial nutrients such as CLA, vitamins and minerals compared to cows brought up on conventional feed. This is clearly important for whey protein concentrates as they retain many of these nutrients, but not so important for isolates.
Most whey protein brands like to make their whey sound like the most advanced and nutritious whey made with super secret and unique processes, but the reality is there are only a few ways whey protein can be made. It is filtered and concentrated either through a type of membrane filtration (which generally produces are more nutritious whey) or ion exchange (which produces a very pure whey) and is then dried/ powdered/ instantised. Processing and sourcing of raw whey does make a difference to the final product, and understanding this will help you pick the right whey powder for your goals. If you enjoyed this article, you might find this one interesting.
- GEA Filtration. Membrane Filtration in the Dairy Industry. Available: http://www.gea.com/global/en/binaries/Membrane%20Filtration%20in%20the%20Dairy%20Industry_tcm11-18227.pdf. Last accessed 5/8/16.
- Tetra Pak. (2016). Whey Processing. Available: http://www.dairyprocessinghandbook.com/chapter/whey-processing. Last accessed 5/8/16.
- Jennifer Sutherland. (2013). Membrane vs. Ion Exchange – Which Process is Best for Whey Protein Powder?. Milk Specialistes. (6)
- Mary Ann Liebert. (2000). Whey Protein Concentrates With and Without Immunoglobulins: A Review. JOURNAL OF MEDICINAL FOOD. 3 (1), 1-13.
- C. Anandharamakrishnan . (2007). Effects of Process Variables on the Denaturation of Whey Proteins during Spray Drying. Drying Technology: An International Journal. 25 (5), 799-807.
- Heinz-Gerhard Kessler and Hans-Joachim Beyer. (1991). Thermal denaturation of whey proteins and its effect in dairy technology . Int. J. Biol. Macromol. 13 (6), 165-174.
- GE Lifesciences (2014). Cross Flow Micro Filtration. Swedeb: GE Lifescience. 1-82.
- Jay R. Hoffman. (2004). PROTEIN – WHICH IS BEST? . Journal of Sports Science and Medicine. 3 (5), 118-130.
- O Power. (2009). Human insulinotropic response to oral ingestion of native and hydrolysed whey protein. Amino Acids. 37 (2), 333-9.
- Koopman R. (2009). Ingestion of a protein hydrolysate is accompanied by an accelerated in vivo digestion and absorption rate when compared with its intact protein.. Am J Clin Nutr. 90 (1), 106-15.