hydrolyzed protein

{{Short description|Solution derived from the hydrolysis of a protein into its component amino acids and peptides}}

Hydrolyzed protein is a solution derived from the hydrolysis of a protein into its component amino acids and/or peptides. Hydrolyzing down to the amino acid level is most commonly achieved using prolonged heating with hydrochloric acid.{{Ullmann|first1=Karlheinz |last1=Drauz|first2=Ian|last2=Grayson|first3=Axel |last3=Kleemann|first4=Hans-Peter|last4=Krimmer|first5=Wolfgang|last5=Leuchtenberger |first6=Christoph|last6=Weckbecker|year=2006| doi=10.1002/14356007.a02_057.pub2|title=Amino Acids}} Hydrolyzing down to the peptide level can be achieved with an enzyme such as pancreatic protease to simulate the naturally occurring hydrolytic process.

Uses

= Chemistry =

Protein hydrolysis is a useful route to the isolation of individual amino acids.{{cite journal | last1 = Silverman | first1 = S.N. | last2 = Phillips | first2 = A.A. | last3 = Weiss | first3 = G.M. | last4 = Wilkes | first4 = E.B. | last5 = Eiler | first5 = J.M. | last6 = Sessions | first6 = A.L. | title = Practical considerations for amino acid isotope analysis | journal = Organic Geochemistry | date = 2022 | doi = 10.1016/j.orggeochem.2021.104345 | volume = 164 | page = 104345| bibcode = 2022OrGeo.16404345S | s2cid = 245556854 | doi-access = free }} Examples include cystine from hydrolysis of hair,{{OrgSynth | last1 = Gortner|first1=R. A.|first2=W. F.|last2=Hoffman | title = l-Cystine | volume= 5 | page= 39| year = 1925| doi= 10.15227/orgsyn.005.0039}} tryptophan from casein,{{cite journal|doi=10.15227/orgsyn.010.0100 |last1=Cox|first1=G.J.|last2=King|first2=H. | title = L-Tryptophane | volume= 10 | pages = 100 | year = 1930 | url=http://www.orgsyn.org/demo.aspx?prep=CV2P0612|journal=Org. Synth.|url-access=subscription }} histidine from red blood cells,{{cite journal|doi=10.15227/orgsyn.018.0043|title=L-Histidine Monohydrochloride|journal=Organic Syntheses|volume=18|pages=43|year=1938|first1=G. L.|last1=Foster|first2=D.|last2=Shemin}} and arginine from gelatin.{{cite journal|title=d-Arginine Hydrochloride|first1=E.|last1=Brand |first2=M.|last2=Sandberg|journal=Org. Synth.|year=1932|volume=12|page=4|doi=10.15227/orgsyn.012.0004}}

= Food =

Protein hydrolysis release savory free amino acids (especially glutamic acid) and peptides. Hydrolyzed vegetable protein and yeast extract are commonly used as flavor enhancers (sources of umami) as a result. The non-protein components in these products also contribute to the flavor.{{cite journal |last1=Kale |first1=Prajyoti |last2=Mishra |first2=Anusha |last3=Annapure |first3=Uday S. |title=Development of vegan meat flavour: A review on sources and techniques |journal=Future Foods |date=June 2022 |volume=5 |pages=100149 |doi=10.1016/j.fufo.2022.100149|doi-access=free }}

Protein hydrolysis also increases their digestibility and rate of digestion.{{cite journal |last1=Hsu |first1=C |last2=Utterback |first2=PL |last3=Parsons |first3=CM |last4=Marx |first4=F |last5=Guldenpfennig |first5=R |last6=de Godoy |first6=MRC |title=Standardized amino acid digestibility and protein quality in extruded canine diets containing hydrolyzed protein using a precision-fed rooster assay. |journal=Journal of Animal Science |date=3 January 2023 |volume=101 |doi=10.1093/jas/skad289 |pmid=37638674|pmc=10503644 }}{{cite journal |last1=Koopman |first1=R |last2=Crombach |first2=N |last3=Gijsen |first3=AP |last4=Walrand |first4=S |last5=Fauquant |first5=J |last6=Kies |first6=AK |last7=Lemosquet |first7=S |last8=Saris |first8=WH |last9=Boirie |first9=Y |last10=van Loon |first10=LJ |title=Ingestion of a protein hydrolysate is accompanied by an accelerated in vivo digestion and absorption rate when compared with its intact protein. |journal=The American Journal of Clinical Nutrition |date=July 2009 |volume=90 |issue=1 |pages=106–15 |doi=10.3945/ajcn.2009.27474 |pmid=19474134}} Some hydrolyzed beef protein powders are used for specialized diets for athletes.{{cite journal |last1=Sharp |first1=Matthew |last2=Shields |first2=Kevin |last3=Lowery |first3=Ryan |last4=Lane |first4=Jason |last5=Partl |first5=Jeremy |last6=Holmer |first6=Chase |last7=Minevich |first7=Julie |last8=Souza |first8=Eduardo De |last9=Wilson |first9=Jacob |title=The effects of beef protein isolate and whey protein isolate supplementation on lean mass and strength in resistance trained individuals - a double blind, placebo controlled study |journal=Journal of the International Society of Sports Nutrition |date=21 September 2015 |volume=12 |issue=Suppl 1 |pages=P11 |doi=10.1186/1550-2783-12-S1-P11 |pmc=4595383 |doi-access=free }}

Protein hydrolysis can be used to destroy epitopes involved in recognition by antibodies involved in allergy. "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."{{cite journal |last1=Burnett |first1=Christina |last2=Bergfeld |first2=Wilma F. |last3=Belsito |first3=Donald V. |last4=Hill |first4=Ronald A. |last5=Klaassen |first5=Curtis D. |last6=Liebler |first6=Daniel C. |last7=Marks |first7=James G. |last8=Shank |first8=Ronald C. |last9=Slaga |first9=Thomas J. |last10=Snyder |first10=Paul W. |last11=Andersen |first11=F. Alan |last12=Heldreth |first12=Bart |title=Safety Assessment of Hydrolyzed Wheat Protein and Hydrolyzed Wheat Gluten as Used in Cosmetics |journal=International Journal of Toxicology |date=May 2018 |volume=37 |issue=1_suppl |pages=55S–66S |doi=10.1177/1091581818776013|pmid=29761728 |s2cid=46889452 |doi-access=free }} As a result, it has been used to reduce the allergenicity of infant formula: 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,[https://web.archive.org/web/20161019151802/http://www.fda.gov/downloads/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/UCM517122.pdf Labeling of Infant Formula: Guidance for Industry] U.S. Food and Drug Administration (2016) Accessed 11 December 2017. but a meta-analysis published the same year shows insufficient evidence for this use.{{cite journal | vauthors = Boyle RJ, Ierodiakonou D, Khan T, Chivinge J, Robinson Z, Geoghegan N, Jarrold K, Afxentiou T, Reeves T, Cunha S, Trivella M, Garcia-Larsen V, Leonardi-Bee J | title = Hydrolysed formula and risk of allergic or autoimmune disease: systematic review and meta-analysis | journal = BMJ | volume = 352 | pages = i974 | date = March 2016 | pmid = 26956579 | pmc = 4783517 | doi = 10.1136/bmj.i974 }}

= 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. 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.{{cite journal |last1=Cave |first1=Nicholas J. |title=Hydrolyzed Protein Diets for Dogs and Cats |journal=Veterinary Clinics of North America: Small Animal Practice |date=November 2006 |volume=36 |issue=6 |pages=1251–1268 |doi=10.1016/j.cvsm.2006.08.008 |pmid=17085233 |url=https://www.researchgate.net/publication/6712297}}

Hydrolysing a usually indigestible protein can provide an additional source of digestible protein. An example of this is hydrolyzed feather meal, made from keratin-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.{{cite web |title=Feather meal |url=https://www.feedipedia.org/node/213 |website=Feedipedia |language=en}}

= 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 and potentially also sulfur. Hydrolyzed keratin from chicken feather is the most common type,{{cite journal |last1=Hadas |first1=Aviva |last2=Kautsky |first2=Larissa |title=Feather meal, a semi-slow-release nitrogen fertilizer for organic farming |journal=Fertilizer Research |date=1994 |volume=38 |issue=2 |pages=165–170 |doi=10.1007/BF00748776}} though other kinds of waste proteins (e.g. waste wool, waste fish) are also re-used this way.{{cite journal |last1=Nelly Noah Metomo |first1=Flore Nadine |last2=Tayi |first2=Fatima |last3=Younes |first3=Essamlali |last4=Amadine |first4=Othmane |last5=Zahouily |first5=Mohamed |title=Production of sheep wool keratin hydrolysate and evaluation of its effectiveness in promoting maize cultivation |journal=Journal of Environmental Management |date=August 2024 |volume=366 |pages=121648 |doi=10.1016/j.jenvman.2024.121648|pmid=39018864 |bibcode=2024JEnvM.36621648N }}{{cite journal |last1=Zhao |first1=Jiancheng |last2=Ni |first2=Huijing |last3=Wang |first3=Bo |last4=Yang |first4=Zhenya |title=Fish protein fertilizer serves as a sustainable alternative, improving soil properties, bamboo growth and shoots yield in Lei bamboo forests |journal=Scientific Reports |date=5 February 2025 |volume=15 |issue=1 |page=4363 |doi=10.1038/s41598-025-88503-5|pmid=39910135 |pmc=11799177 |bibcode=2025NatSR..15.4363Z }}

Hydrolyzed protein fertilizer is considered an organic fertilizer.{{cite journal |last1=Hadas |first1=Aviva |last2=Kautsky |first2=Larissa |title=Feather meal, a semi-slow-release nitrogen fertilizer for organic farming |journal=Fertilizer Research |date=1994 |volume=38 |issue=2 |pages=165–170 |doi=10.1007/BF00748776}} It contains a high amount of available nitrogen, and unlike unhydrolyzed feather meal, tends to release the nitrogen quickly.{{cite journal |last1=Sobucki |first1=Lisiane |last2=Ramos |first2=Rodrigo Ferraz |last3=Gubiani |first3=Elci |last4=Brunetto |first4=Gustavo |last5=Kaiser |first5=Douglas Rodrigo |last6=Daroit |first6=Daniel Joner |title=Feather hydrolysate as a promising nitrogen-rich fertilizer for greenhouse lettuce cultivation |journal=International Journal of Recycling of Organic Waste in Agriculture |date=December 2019 |volume=8 |issue=S1 |pages=493–499 |doi=10.1007/s40093-019-0281-7|doi-access=free |bibcode=2019IJROW...8S.493S }} It helps the growth of soil microbes and improves soil quality.{{cite journal |last1=Bhari |first1=R |last2=Kaur |first2=M |last3=Sarup Singh |first3=R |title=Chicken Feather Waste Hydrolysate as a Superior Biofertilizer in Agroindustry. |journal=Current Microbiology |date=June 2021 |volume=78 |issue=6 |pages=2212–2230 |doi=10.1007/s00284-021-02491-z |pmid=33903939}}

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; further hydrolysis leads to reduced bitterness.{{cite journal |last1=Li |first1=Li |last2=Yang |first2=Zuo-Yi |last3=Yang |first3=Xiao-Qun |last4=Zhang |first4=Gui-He |last5=Tang |first5=Shu-Ze |last6=Chen |first6=Feng |title=Debittering effect of Actinomucor elegans peptidases on soybean protein hydrolysates |journal=Journal of Industrial Microbiology & Biotechnology |date=January 2008 |volume=35 |issue=1 |pages=41–47 |doi=10.1007/s10295-007-0264-y |pmid=17943333 }}

= 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 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.