Hydrolyzed protein is a solution derived from the

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

of a protein into its component

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...

s and/or

peptide Peptides are short chains of amino acids linked by peptide bonds. A polypeptide is a longer, continuous, unbranched peptide chain. Polypeptides that have a molecular mass of 10,000 Da or more are called proteins. Chains of fewer than twenty am ...

s. Hydrolyzing down to the amino acid level is most commonly achieved using prolonged heating with

hydrochloric acid Hydrochloric acid, also known as muriatic acid or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is ...

. Hydrolyzing down to the peptide level can be achieved with an

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

such as

pancreatic The pancreas (plural pancreases, or pancreata) is an organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine ...

protease A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalysis, catalyzes proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the formation of new protein products ...

to simulate the naturally occurring hydrolytic process.

Uses

Chemistry

Protein hydrolysis is a useful route to the isolation of individual amino acids. Examples include

cystine Cystine is the oxidized derivative of the amino acid cysteine and has the formula (SCH2CH(NH2)CO2H)2. It is a white solid that is poorly soluble in water. As a residue in proteins, cystine serves two functions: a site of redox reactions and a mec ...

from hydrolysis of hair,

tryptophan Tryptophan (symbol Trp or W) is an α-amino acid that is used in the biosynthesis of proteins. Tryptophan contains an α-amino group, an α-carboxylic acid group, and a side chain indole, making it a polar molecule with a non-polar aromat ...

from

casein Casein ( , from Latin ''caseus'' "cheese") is a family of related phosphoproteins (CSN1S1, αS1, aS2, CSN2, β, K-casein, κ) that are commonly found in mammalian milk, comprising about 80% of the proteins in cow's milk and between 20% and 60% of ...

histidine Histidine (symbol His or H) is an essential amino acid that is used in the biosynthesis of proteins. It contains an Amine, α-amino group (which is in the protonated –NH3+ form under Physiological condition, biological conditions), a carboxylic ...

from red blood cells, and

arginine Arginine is the amino acid with the formula (H2N)(HN)CN(H)(CH2)3CH(NH2)CO2H. The molecule features a guanidinium, guanidino group appended to a standard amino acid framework. At physiological pH, the carboxylic acid is deprotonated (−CO2−) a ...

from

gelatin Gelatin or gelatine () is a translucent, colorless, flavorless food ingredient, commonly derived from collagen taken from animal body parts. It is brittle when dry and rubbery when moist. It may also be referred to as hydrolyzed collagen, coll ...

Food

Protein hydrolysis release savory free amino acids (especially

glutamic acid Glutamic acid (symbol Glu or E; known as glutamate in its anionic form) is an α- amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a non-essential nutrient for humans, meaning that the human body can ...

) and peptides.

Hydrolyzed vegetable protein Hydrolyzed vegetable protein (HVP) products are foodstuffs obtained by the hydrolysis of protein, and have a meaty, savory taste similar to broth (bouillon). Regarding the production process, a distinction can be made between acid-hydrolyzed v ...

and

yeast extract Yeast extracts consist of the cell contents of yeast without the cell walls; they are used as food additives or flavorings, or as nutrients for bacterial culture Growing media, media. They are often used to create savoury flavors and umami tast ...

are commonly used as

flavor enhancer A flavoring (or flavouring), also known as flavor (or flavour) or flavorant, is a food additive that is used to improve the taste or smell of food. It changes the perceptual impression of food as determined primarily by the chemoreceptors of t ...

s (sources of

umami Umami ( from ), or savoriness, is one of the five basic tastes. It is characteristic of broths and cooked meats. People taste umami through taste receptors that typically respond to glutamates and nucleotides, which are widely present in me ...

) as a result. The non-protein components in these products also contribute to the flavor. Protein hydrolysis also increases their digestibility and rate of digestion. Some hydrolyzed beef protein powders are used for specialized diets for athletes. Protein hydrolysis can be used to destroy

epitope An epitope, also known as antigenic determinant, is the part of an antigen that is recognized by the immune system, specifically by antibodies, B cells, or T cells. The part of an antibody that binds to the epitope is called a paratope. Although e ...

s involved in recognition by

antibodies An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as bacteria and viruses, including those that caus ...

involved in

allergy Allergies, also known as allergic diseases, are various conditions caused by hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include Allergic rhinitis, hay fever, Food allergy, food al ...

. "An allergen must have at least 2 IgE-binding epitopes, and each epitope must be at least 15 amino acid residues long, to trigger a type 1 hypersensitivity reaction." As a result, it has been used to reduce the allergenicity of

infant formula Infant formula, also called baby formula, simply formula (American English), formula milk, baby milk, or infant milk (British English), is a manufactured food designed and marketed for feeding to babies and infants under 12 months of age, ...

: Reducing the size of cow milk proteins in the formula makes it more suitable for consumption by babies suffering from milk protein intolerance. The US FDA has approved a label for this usage of partially-hydrolyzed proteins in 2017, but a

meta-analysis Meta-analysis is a method of synthesis of quantitative data from multiple independent studies addressing a common research question. An important part of this method involves computing a combined effect size across all of the studies. As such, th ...

published the same year shows insufficient evidence for this use.

Animal feed

Food allergies also occur in cats and in dogs. When the allergy is due to a protein in the food, the issue can be avoided by hydrolyzing the proteins into smaller components. Hydrolyzed protein is therefore used in specially formulated hypoallergenic pet foods. Partially hydrolyzed protein may also increase the development of

immune tolerance Immune tolerance, also known as immunological tolerance or immunotolerance, refers to the immune system's state of unresponsiveness to substances or tissues that would otherwise trigger an immune response. It arises from prior exposure to a specif ...

. The increased protein digestibility is also potentially useful for pets with digestive issues such as inflammatory bowel disease, being in recovery from acute enteritis, and exocrine pancreatic insufficiency. Hydrolysing a usually indigestible protein can provide an additional source of digestible protein. An example of this is hydrolyzed

feather meal Feather meal or Feather powder, is a byproduct of processing poultry; it is made from poultry feathers by partially grinding them under elevated heat and pressure, and then grinding and drying. Although total nitrogen levels are fairly high (up to ...

, made from

keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. It is the key structural material making up Scale (anatomy), scales, hair, Nail (anatomy), nails, feathers, horn (anatomy), horns, claws, Hoof, hoove ...

-rich waste features from the poultry industry. With partial hydrolysis, it becomes a cheap, low-carbon source of protein that is digestible by ordinary livestock and pets. Although it retains the poor amino acid profile from feather, the good digestibility and high protein content makes it a good companion to other protein sources.

Fertilizer

Hydrolyzing a protein improves the digestibility not only for animals, but also for soil microbes. As a result, it becomes useful as a fertilizer providing

nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...

and potentially also

sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...

. Hydrolyzed keratin from chicken feather is the most common type, though other kinds of waste proteins (e.g. waste wool, waste fish) are also re-used this way. Hydrolyzed protein fertilizer is considered an

organic fertilizer Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ Chemistry * Organic matter, matter that has come from a once-living organism, is capable of decay or is the product ...

. It contains a high amount of available nitrogen, and unlike unhydrolyzed feather meal, tends to release the nitrogen quickly. It helps the growth of soil microbes and improves soil quality.

Issues

Bitterness

Partially hydrolyzed protein can contain peptides that taste bitter, as more and more hydrophobic side chains are exposed. With soy protein, maximum bitterness occur at a mean size of 2 to 4

kDa The dalton or unified atomic mass unit (symbols: Da or u, respectively) is a unit of mass defined as of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at rest. It is a non-SI unit accepted f ...

; further hydrolysis leads to reduced bitterness.

Incomplete epitope destruction

If a hydrolyzed protein for use in hypoallergenic food is not sufficiently hydrolyzed, it can still contain epitopes and trigger an allergic response.

Osmolarity

Hydrolyzed protein has higher

osmolarity Osmotic concentration, formerly known as osmolarity, is the measure of solute concentration, defined as the number of osmoles (Osm) of solute per litre (L) of solution (osmol/L or Osm/L). The osmolarity of a solution is usually expressed as Osm/ ...

than the original protein. As a result, it could make the food act more like a hyperosmotic laxative and lead to diarrhea. Infant formulas with hydrolyzed protein has been blamed for causing diarrhea. Dogs and adult humans do not appear to be affected, and dogs with gastrointestinal signs of allergy do see their stool improve on hypoallergenic diets.

References

{{DEFAULTSORT:Hydrolyzed Protein Food additives Protein structure Umami enhancers