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Whey protein hydrolysates represent the top tier of whey protein supplements. They are generally the most expensive and offer the most benefits for muscle recovery and growth. But just like their counterparts (i.e. whey isolate and concentrate), there is a big difference in the quality and variety of hydrolysed whey proteins. If you are ‘wheying’ up your first purchase of hydrolysed whey, it’s important that you understand exactly what a hydrolysed whey protein is and how to differentiate between different varieties.

Hydrolysis Basics

First things first: hydrolysed whey (as its name suggests) is whey protein that has been hydrolysed or ‘broken down’ into smaller fragments; generally referred to as peptides. A useful analogy is to think of hydrolysed whey protein as letters and words; where amino acids are the individual letters and the words are the peptides. Just like words, peptides can take on a variety of shapes and sizes. Peptides can be as small as two amino acids and as large as 50 amino acids. Whey protein hydrolysate is manufactured by submitting whey protein to digestive enzymes. These digestive enzymes cleave the whey protein at specific points along the protein chain; splitting the larger protein molecules into smaller ones2. The end result is a complex mixture of free amino acids and peptides of different chain length. So it’s largely the digestive enzymes used to hydrolyse whey protein that determine the particular specifications and composition of the resultant hydrolysed whey protein. Understanding the difference in specifications between hydrolysed whey proteins is the key to making an empowered decision about the best hydrolysate for your needs.

Benefits of Whey Protein Hydrolysates

Before delving into the detail about how whey hydrolysates are manufactured and their differences, it's useful to be reminded of their many benefits. Whey protein hydrolysates have been shown to have a number of distinct benefits over normal whey proteins. These benefits are principally the result of the unique structure of hydrolysed whey proteins and their respective peptide content. Benefits include:

  • More rapid uptake of amino acids compared with whole proteins or free-form amino acid mixtures11, 12
  • Greater utilisation and nitrogen retention than intact proteins or amino acids14, 15
  • Greater insulinotropic (i.e. insulin boosting) effect13
  • Improved uptake of branched-chain amino acids12
  • Improved tolerance in individuals with diseased gastrointestinal tracts
  • Quicker strength recovery following eccentric exercise
  • Reduced delayed-onset muscle soreness (DOMS)

Protein hydrolysates are also known to possess a variety of biologically active peptides, which have various therapeutic applications from blood pressure to weight control. In fact the development of specific whey protein hydrolysates and whey peptides for a variety of indications/applications has been one of the most rapidly developing areas of dairy technology in sports nutrition10. Most dairy protein raw material suppliers now offer a range of whey protein hydrolysates, which have specific applications such as:

  • Reduced blood pressure & arterial stifness6, 8
  • Fat loss9, 16
  • Improved glucose uptake and glycogen storage17-19
  • Normalising blood glucose concentration in type 2 diabetics9, 20, 21

Whether its whey protein hydrolysate or very specific whey-derived peptides, manufacturing the material is a more sophisticated process than your average whey protein, and naturally comes at a higher price. Whey hydrolysates and peptides have specific manufacturing processes by virtue of the digestive enzymes that are used during production. These are discussed in detail below.

Degree of Hydrolysis

The degree of hydrolysis is a commonly cited specification for hydrolysed proteins. It is designed to give an indication of the number of peptide bonds that are broken during enzyme breakdown and therefore the average size of the peptides present. It is defined as the proportion of the total number of peptide bonds that are cleaved during hydrolysis1. So with an increasing degree of hydrolysis, there are a greater number of broken peptides and therefore a higher number of smaller peptide fragments. Values for degree of hydrolysis can range from as little as 5% right up to over 20%. Generally speaking, the higher the degree of hydrolysis –the higher the peptide content and the higher the cost of the whey protein hydrolysate. This is also the reason why most companies/brands don’t disclose the degree of hydrolysis; despite it being standard information on every specification for whey protein hydrolysate supplied to them by raw material manufacturers.

Molecular Weight Distribution

The molecular weight distribution is another commonly cited specification of hydrolysed whey proteins that is directly related to degree of hydrolysis. The table below shows a sample molecular weight distribution for a protein with a high degree of hydrolysis. Typically the weight distribution is divided into different molecular weight ranges which correspond to different peptide sizes. As a general rule, single amino acids are usually below 200 Daltons (Da), while dipeptides and tripeptides are usually in the range of 200 – 500 Da. The particular hydrolysate shown in the table below has a relatively high dipeptide and tripeptide content of around 20%. The molecular weight distribution profile for a given whey protein hydrolysate is an even more advanced specification than degree of hydrolysis and you can almost guarantee you will not see it on the label of any whey protein hydrolysate. Although one bit of information that is sometimes disclosed is the dipeptide and tripeptide content. This relates directly back to the molecular weight distribution profile as highlighted previously.

Molecular Weight Distribution Profile for Whey Protein Hydrolysate
For readers that like to know all the nitty gritty details on how much the average amino acid/peptide weighs; the table below shows the molecular weight for each of the common amino acids that make up your average whey protein. With some rough calculations, it’s possible to deduce that most peptides (i.e. chains of 50 amino acids and under) are below 5000 Daltons.


Amino Acid

Molecular Weight – Daltons (Da)







Aspartic acid




Glutamic acid































Effect of Digestive Enzymes on Dipeptide & Tripeptide Content

The degree of hydrolysis and the ensuing molecular weight distribution are both determined largely by the type of enzyme(s) used to break down whey protein. It follows that there are different types of enzymes, which tend to produce characteristic molecular weight distribution profiles dependant on the protein. One example of a popular class of enzymes is endopeptidases. These enzymes cleave peptide bonds within the protein molecule as opposed to breaking peptide bonds from the end of the molecule. Some popular examples include trypsin, chymotrypsin and pepsin3. Trypsin and chymotrypsin work in alkaline conditions, while pepsin works best in an acidic environment3. The enzymes also differ by virtue of the specific amino acids they cleave. For example, trypsin and chymotrypsin cleave peptide bonds with tryptophan, tyrosine and phenylalanine residues, while pepsin cleaves peptide bonds with arginine and lysine residues3. So one can begin to appreciate how the particular mix of enzymes used can affect the amino acid and peptide composition of a whey protein hydrolysate.

Proline Peptide Bonds & Bitterness

However, one limitation common to most conventional endopeptidases is the inability to cleave between proline residues, which invariably limits the extent of hydrolysis. To produce a whey protein hydrolysate with a high degree of hydrolysis and therefore a high content of dipeptides and tripeptides, whey proteins generally need to be subjected to a combination of a common endopeptidase together with a proline-specific endoprotease. As shown below, these enzymes cleave whey proteins at proline residues, with the end result being smaller peptide fragments4. These specially developed proline-peptidases come from select microorganisms, with bacillus subtilis and aspergillus niger4, 5 examples of two common ones.

Debittering whey protein hydrolysate with proline-specific endoproteases

As illustrated above, another important aspect of proline-specific endoproteases is that they also decrease the inherent bitterness of whey hydrolysates4, 5. The concentration of proline residues in peptides has been shown to be closely related to bitterness, thus explaining the debittering effect of proline-specific endoproteases4, 5. It is only by combining conventional endoproteases with proline-specific endoproteases that whey protein hydrolysates with high dipeptide and tripeptide content (i.e. >40%) can be achieved.

This level of detail concerning the types of enzymes used to produce a particular hydrolysed whey protein is not typically disclosed by manufacturers because of its complexity and the fact that it forms a large part of the supplements intellectual property. Nonetheless, advance supplement users may appreciate knowing a bit more about how manufacturers produce their whey protein hydrolysates and the factors that govern their peptide profile.

Whey Protein Hydrolysates Into the Future

Whey protein hydrolysates remain one of the most exciting areas of product development in sports nutrition. This is because of the limitless types of peptides that can be produced by custom hydrolysis of whey proteins. Whey protein hydrolysates and whey peptides will continue to develop in the near future, however, food technologists and engineers will need to look at means and ways to bring down the costs of manufacturing so that the multiple types of whey hydrolysates and peptides are affordable for the broader health and fitness market.


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2. Thomson RL & Buckley JD. Protein hydrolysates and tissue repair. Nutrition Research Reviews. 2011;24:191–197.
3. Adjonu R, et al. Screening of whey protein isolate hydrolysates for their dual functionality:Influence of heat pre-treatment and enzyme specificity. Food Chemistry. 2013; 136:1435–1443.
4. Edens L, et al. Extracellular prolyl endoprotease from aspergillus niger and its use in the debittering of protein hydrolysates. J Agric Food Chem. 2005;53(20):7950-7.
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7. Tang JE, et al. Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men. J Appl Physiol. 2009; 107:987–992.
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12. Morifuji M, et al. Branched-chain amino acid-containing dipeptides, identified from whey protein hydrolysates, stimulate glucose uptake rate in L6 myotubes and isolated skeletal muscles. J Nutr Sci Vitaminol. 2009;55:81-86.
13. Isabelle ME, et al. Inhibition of dipeptidyl peptidase (DPP)-IV and α‑glucosidase activities by pepsin-treated whey proteins. J Agric Food Chem. 2013;61:7500−7506.
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20. Pennings B, et al. Whey protein stimulates postprandial muscle protein accretion more effectively than do casein and caseinhydrolysate in older men. Am J Clin Nutr. 2011 May;93(5):997-1005.
21. Cribb PJ, et al. The effect of whey isolate and resistance training on strength, body composition, and plasma glutamine. Int J Sport Nutr Exerc Metab. 2006;16(5):494-509.

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