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==Uses==

===Paint===
[[File:Caseinaufbereitung.jpg|thumb|Casein preparation in an old etching operation in Müllheim]]
[[Casein paint]] is a fast-drying, water-soluble medium used by artists. Casein paint has been used since ancient Egyptian times as a form of [[tempera]] paint, and was widely used by commercial illustrators as the material of choice until the late 1960s when, with the advent of [[acrylic paint]], casein became less popular.<ref>{{Cite book|title=Reader's Digest Crafts & Hobbies|publisher=Reader's Digest Association|year=1979|isbn=978-0-89577-063-9|veditors=Weiss D, Chace S|pages=[https://archive.org/details/readersdigestcra00weis/page/223 223]|url-access=registration|url=https://archive.org/details/readersdigestcra00weis/page/223}}</ref><ref>{{Cite encyclopedia|title=Acrylic painting|date=2008|encyclopedia=The Grove Encyclopedia of Materials and Techniques in Art|publisher=Oxford University Press|url=https://books.google.com/books?id=mkJfbdTS--UC&q=casein+acrylic&pg=PA1| veditors = Ward GW |page=2 |isbn= 978-0-19-531391-8}}</ref>  It is still widely used by scenic painters, although acrylic has made inroads in that field as well.<ref>{{Cite book|url=https://books.google.com/books?id=9HQR0gmvyoMC&q=casein+acrylic&pg=PA281|title=Scenic Design And Lighting Techniques: A Basic Guide for Theatre|vauthors=Gloman CB, Napoli R|publisher=Taylor & Francis|year=2007|isbn=978-0-240-80806-2|pages=281–2}}</ref>

===Glue===
[[File:Casein glue preparation.jpg|thumb|upright=3|Preparing casein glue]]
Casein-based glues are formulated from casein, water, and alkalis (usually a mix of [[hydrated lime]] and [[sodium hydroxide]]). Milk is [[skim milk|skimmed]] to remove the fat, then the milk is [[sour milk|soured]] so that the casein is precipitated as [[milk curd]]. The curd is washed (removing the [[whey]]), and then the curd is pressed to squeeze out the water (it may even be dried to a powder). The casein is mixed with alkali (usually both sodium and calcium hydroxide) to make glue. Glues made with different mixes of alkalis have different properties. Preservatives may also be added.<ref>{{cite book |author=Forest Products Laboratory |author2=Forest Service |author3=US Department of Agriculture |title=Casein glues: their manufacture, preparation, and application |via=Oregon State Library |date=April 1961 |url=http://link.library.in.gov/portal/Casein-glues--their-manufhttps://ir.library.oregonstate.edu/dspace/bitstream/1957/882/1/FPL_280ocr_rev.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://ir.library.oregonstate.edu/dspace/bitstream/1957/882/1/FPL_280ocr_rev.pdf |archive-date=2022-10-09 |volume=280| language=en}}</ref><ref>{{cite web |title=Chemistry Casein Glue - Activity |url=https://www.teachnlearnchem.com/Matter_and_Energy/PDF/casein%20glue.pdf}}</ref>

They were popular for woodworking, including for aircraft, as late as the [[de Havilland Albatross|de Havilland ''Albatross'']] airliner in 1939.<ref name="fpl.fs.fed.us">{{cite web|url=http://www.fpl.fs.fed.us/documnts/fplrn/fplrn158.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.fpl.fs.fed.us/documnts/fplrn/fplrn158.pdf |archive-date=2022-10-09 |url-status=live|title=Casein Glues: Their Manufacture, Preparation, and Application|date=1967|publisher=[[United States Department of Agriculture|USDA]]}}</ref><ref>{{cite web|url=http://www.soyinfocenter.com/HSS/if_laucks_and_soybean_glue.php|title=Pioneering Soy Protein Companies: I. F. Laucks, The Glidden Co., Rich Products, Gunther Products, Griffith Laboratories| vauthors = Shurtleff W, Aoyagi A|date=2004|work=soyinfocenter.com|access-date=3 Sep 2015}}</ref>

Casein glue is also used in [[transformer]] manufacturing (specifically transformer board) due to its oil permeability.<ref>{{cite web|url=http://www.weidmann-electrical.com/en/markets-a-products/board/cellulose-based/laminated-board|title=Laminated Board|date=2011|publisher=WICOR HOLDING AG|archive-url=https://web.archive.org/web/20111222012222/http://www.weidmann-electrical.com/en/markets-a-products/board/cellulose-based/laminated-board|archive-date=22 December 2011|access-date=11 Oct 2012}}</ref>

[[Elmer's Products|Elmer's Glue-All, Elmer's School Glue]] and many other Borden adhesives were originally made from casein. While one reason was its non-toxic nature, a primary factor was that it was economical to use. Towards the end of the 20th century, Borden replaced casein in all of its popular adhesives with synthetics like [[Polyvinyl acetate|PVA]].

While largely replaced with synthetic resins, casein-based glues still have a use in certain niche applications, such as laminating fireproof doors and the labeling of bottles.<ref name="fpl.fs.fed.us"/><ref>{{Cite book|title=Coatings Materials and Surface Coatings|vauthors=Lambuth A|publisher=CRC Press|year=2006|isbn=978-1-4200-4405-8|veditors=Tracton AA|pages=19-7–19-11|chapter=Soybean, Blood, and Casein Glues|chapter-url=https://books.google.com/books?id=HhUOI1-hhjYC&pg=SA19-PA7}}</ref><ref>{{Cite book|title=Tappi PLACE Division Conference|vauthors=Forsyth RS|publisher=TAPPI|year=2004|isbn=1-59510-062-8|location=Atlanta, Ga.|page=33|chapter=Waterborne Adhesives for Bottle Labeling|oclc=57487618}}</ref> Casein glues thin rapidly with increasing temperature, making it easy to apply thin films quickly to label jars and bottles on a production line.<ref>{{cite web |title=Casein glues |url=https://www.intercol.info/en/?page_id=85 |website=Adhesives}}</ref>

===Food===
Several foods, creams, and toppings all contain a variety of caseinates. Sodium caseinate acts as a greater food additive for stabilizing processed foods; however, companies could opt to use [[calcium caseinate]] to increase calcium content and decrease sodium levels in their products.<ref name=":0">{{cite patent | inventor = Merrill RK, Li J | assign = Leprino Foods Co | title = Micellar casein for corree creamers and other dairy products. | country = US | number = 20160374360 | pubdate = 29 December 2016 | url = https://patents.google.com/patent/US20160374360A1/en }}</ref>

Caseins for food additive use are produced by adding an acid to milk, which causes the casein to precipitate out as ''acid casein''. By adding a base such as sodium hydroxide or calcium hydroxide to acid casein, a pure caseinate or ''casein salt'' is produced.<ref name="Badem">{{cite journal |last1=Badem |first1=A |last2=Ucar |first2=G |title=Production of caseins and their usages |journal=International Journal of Food Science and Nutrition |date=January 2017 |volume=2 |issue=1 |page=4-9 |url=https://www.researchgate.net/publication/330674713_Production_of_caseins_and_their_usages |issn=2455-4898}}</ref> "Co-precipate" refers to a mixture of casein and possibly other milk components that went out of the solution with casein. The precipitation can happen either through proteolysis (rennet) or through acid.<ref name="Badem"/>

{| class="wikitable"
|+Caseinate Presence and Function in Different Products<ref name=":1">{{Cite journal|vauthors=El-Bakry M|date=2011|title=Functional and Physicochemical Properties of Casein and its Use in Food and Non-Food Industrial Applications|journal=Chemical Physics Research Journal|volume=4|pages=125–138|id={{ProQuest|1707988596}}}}</ref>
!Product
!Caseinate %
!Type
!Function
|-
|Cheese
|3–28
|Rennet (digested) casein, some products also add [[milk protein concentrate]]<ref name="Badem"/>
|Matrix formation, fat, and water binding
|-
|Ice Cream
|1–7
|Calcium caseinate from milk, added caseinate
|Texture and stabilizer
|-
|Whipped toppings
|2–11
|Added caseinate
|Fat stabilization
|-
|Meat
|2–20
|Added caseinate and co-precipate
|Texture and nutrition
|-
|Pasta
|2–18
|Added caseinate and caseins
|Texture, nutrition, and taste
|-
|Baked goods
|1–15
|Added caseinate and caseins
|Water binding
|}
The main food uses of casein are for powders requiring rapid dispersion into water, ranging from coffee creamers to instant cream soups. Mead Johnson introduced a product in the early 1920s named Casec to ease gastrointestinal disorders and infant digestive problems which were a common cause of death in children at that time.

All caseinates have very efficient emulsifying properties and widely used to make emulsions in foods.<ref>{{Cite journal | vauthors = Courthaudon JL, Girardet JM, Campagne S, Rouhier LM, Campagna S, Linden G, Lorient D |date= March 1999 |title=Surface active and emulsifying properties of casein micelles compared to those of sodium caseinate  |journal=International Dairy Journal |volume=9 |issue=3 |pages=411–412 |doi=10.1016/S0958-6946(99)00111-9 |issn=0958-6946}}</ref><ref name="Braun_2019" />

Casein is also believed to neutralize [[capsaicin]], the active spicy ingredient of [[chili pepper]]s such as [[jalapeño]]s, and [[habanero]]s.<ref>{{cite journal | vauthors = Nolden AA, Lenart G, Hayes JE | title = Putting out the fire - Efficacy of common beverages in reducing oral burn from capsaicin | journal = Physiology & Behavior | volume = 208 | page = 112557 | date = September 2019 | pmid = 31121171 | pmc = 6620146 | doi = 10.1016/j.physbeh.2019.05.018 }}</ref> Milk is often consumed to decrease irritation caused by spicy foods.

====Cheesemaking====
[[File:Production of cheese 1.jpg|thumb|left|Cheesemaking]]
[[Cheese]] consists of proteins and fat from [[milk]], usually the milk of [[Cow milk|cows]], [[Water Buffalo|buffalo]], [[Goat milk|goats]], or [[Sheep milk|sheep]]. It is produced by [[coagulation (milk)|coagulation]] that is caused by destabilization of the casein micelle, which begins the processes of fractionation and selective concentration.<ref name=wiley2002 /> Typically, the milk is acidified and then coagulated by the addition of [[rennet]], containing a [[proteolytic]] [[enzyme]] known as [[Chymosin|rennin]]; traditionally obtained from the stomachs of [[calf (animal)|calves]], but currently produced more often from genetically modified microorganisms. The solids are then separated and pressed into final form.<ref>{{cite web|url=http://biology.clc.uc.edu/fankhauser/Cheese/CHEESE.HTML|title=Fankhauser's Cheese Page| vauthors = Fankhauser DB |date=2007 |archive-url=https://web.archive.org/web/20070925001225/http://biology.clc.uc.edu/Fankhauser/Cheese/CHEESE.HTML|archive-date=25 September 2007|access-date=23 Sep 2007}}</ref>

Unlike many proteins, casein is not coagulated by heat.  During the process of clotting, milk-clotting [[proteases]] act on the soluble portion of the caseins, [[K-casein|κ-casein]], thus originating an unstable [[micelle|micellar]] state that results in clot formation. When coagulated with [[chymosin]], casein is sometimes called '''paracasein'''. Chymosin (EC 3.4.23.4) is an [[aspartic protease]] that specifically [[hydrolysis|hydrolyzes]] the peptide bond in Phe105-Met106 of κ-casein, and is considered to be the most efficient protease for the cheese-making industry (Rao et al., 1998). British terminology, on the other hand, uses the term caseinogen for the uncoagulated protein and casein for the coagulated [[protein]]. As it exists in milk, it is a [[salt (chemistry)|salt]] of [[calcium]].

====Protein supplements====
An attractive property of the casein molecule is its ability to form a gel or clot in the stomach, which makes it very efficient in nutrient supply. The clot is able to provide a sustained slow release of amino acids into the blood stream, sometimes lasting for several hours. This also happens when milk is consumed by an animal: the stomach proteases cause it to form a gel. Cheesemaking using [[rennet]] (see above) replicates this behavior.<ref>{{cite journal | vauthors = Boirie Y, Dangin M, Gachon P, Vasson MP, Maubois JL, Beaufrère B | title = Slow and fast dietary proteins differently modulate postprandial protein accretion | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 94 | issue = 26 | pages = 14930–14935 | date = December 1997 | pmid = 9405716 | pmc = 25140 | doi = 10.1073/pnas.94.26.14930 | doi-access = free | bibcode = 1997PNAS...9414930B }}</ref>

Casein is also a relatively abundant source of protein. One form (without the delayed-gelling property) is ''hydrolyzed casein'', whereby it is [[hydrolysis|hydrolyzed]] by a [[protease]] such as [[trypsin]]. This could result in quicker digestion or direct gel formation. Hydrolyzed forms are noted to taste bitter and such supplements are often refused by infants and lab animals in favor of intact casein.<ref>{{cite journal | vauthors = Field KL, Kimball BA, Mennella JA, Beauchamp GK, Bachmanov AA | title = Avoidance of hydrolyzed casein by mice | journal = Physiology & Behavior | volume = 93 | issue = 1–2 | pages = 189–199 | date = January 2008 | pmid = 17900635 | pmc = 2254509 | doi = 10.1016/j.physbeh.2007.08.010 }}</ref>

===Plastics and fiber===
[[File:White casein Australian Royal Airforce pre-1953 buttons.jpg|thumb|White [[galalith]] [[RAAF]] pre-1953 buttons]]
Some of the earliest plastics were based on casein. In particular, [[galalith]] was well known for use in [[buttons]]. [[Milk fiber]] can be made from extruded casein. [[Lanital]], a fabric made from casein fiber (known as [[Aralac]] in the United States),<ref>{{Cite news |date=1941-11-09 |title=NEW CASEIN FIBER DUE FOR WIDE USE; Aralac, Skim-Milk By-Product, to Go Into Dress, Upholstery, Blanket and Other Fields (Published 1941) |url=https://www.nytimes.com/1941/11/09/archives/new-casein-fiber-due-for-wide-use-aralac-skimmilk-byproduct-to-go.html |access-date=2025-10-22 |language=en}}</ref> was invented in Italy in 1935.<ref>{{Cite journal |date=1937-12-01 |title=Artificial Wool Production in Italy |url=https://www.nature.com/articles/1401090a0 |journal=Nature |language=en |volume=140 |issue=3556 |pages=1090–1090 |doi=10.1038/1401090a0 |issn=1476-4687}}</ref> This material, also referred to as milk cotton, is used in yarn production and can be made from a blend of casein and [[acrylonitrile]], or in some cases, from pure casein.<ref>{{Cite web |title=What is Milk Fabric: Properties, How its Made and Where |url=https://sewport.com/fabrics-directory/milk-fabric |access-date=2025-10-22 |website=Sewport |language=en}}</ref> 

===Medical and dental uses===
Casein-derived compounds are used in [[Remineralisation of teeth|tooth remineralization]] products to stabilize [[amorphous calcium phosphate]] (ACP) and release the ACP onto tooth surfaces, where it can facilitate remineralization.<ref>{{Cite journal| vauthors = Malcmacher L |journal=Dentistry Today|title=Enamel Remineralization: The Medical Model of Practicing multi Dentistry|date=8 February 2011|url=http://www.dentistrytoday.com/hygiene/1164}}</ref><ref>{{cite journal | vauthors = Walker G, Cai F, Shen P, Reynolds C, Ward B, Fone C, Honda S, Koganei M, Oda M, Reynolds E | display-authors = 6 | title = Increased remineralization of tooth enamel by milk containing added casein phosphopeptide-amorphous calcium phosphate | journal = The Journal of Dairy Research | volume = 73 | issue = 1 | pages = 74–78 | date = February 2006 | pmid = 16433964 | doi = 10.1017/S0022029905001482 | s2cid = 43342264 }}</ref><ref name="Chhabra Chhabra pp. 1–10">{{cite journal|vauthors=Chhabra N, Chhabra A|date=2018|title=Enhanced Remineralisation of Tooth Enamel Using Casein Phosphopeptide-Amorphous Calcium Phosphate Complex: A Review|journal=International Journal of Clinical Preventive Dentistry|volume=14|issue=1|pages=1–10|doi=10.15236/ijcpd.2018.14.1.1}}</ref>

Casein and [[gluten]] [[exclusion diet]]s are sometimes used in [[alternative medicine]] for children with [[autism]]. As of 2015 the evidence that such diets have any impact on behavior or cognitive and social functioning in autistic children was limited and weak.<ref>{{cite journal | vauthors = Lange KW, Hauser J, Reissmann A | title = Gluten-free and casein-free diets in the therapy of autism | journal = Current Opinion in Clinical Nutrition and Metabolic Care | volume = 18 | issue = 6 | pages = 572–575 | date = November 2015 | pmid = 26418822 | doi = 10.1097/mco.0000000000000228 | s2cid = 271720 }}</ref><ref name="Cochrane2008">{{cite journal | vauthors = Millward C, Ferriter M, Calver S, Connell-Jones G | title = Gluten- and casein-free diets for autistic spectrum disorder | journal = The Cochrane Database of Systematic Reviews | issue = 2 | article-number = CD003498 | date = April 2008 | pmid = 18425890 | pmc = 4164915 | doi = 10.1002/14651858.CD003498.pub3 | type = Systematic Review }}</ref>{{Update inline|reason=Updated version https://www.ncbi.nlm.nih.gov/pubmed/30938835|date = April 2026}}

=== Nanotechnological uses ===
Casein proteins have potential for use as [[nanomaterials]] due to their readily available source (milk) and their propensity to self-assemble into [[amyloid]] fibrils.<ref>{{cite book | vauthors = Ecroyd H, Garvey M, Thorn DC, Gerrard JA, Carver JA | chapter = Amyloid Fibrils from Readily Available Sources: Milk Casein and Lens Crystallin Proteins | series = Methods in Molecular Biology | title = Protein Nanotechnology | volume = 996 | pages = 103–117 | date = 2013 | pmid = 23504420 | doi = 10.1007/978-1-62703-354-1_6 | publisher = Humana Press | isbn = 978-1-62703-353-4 | place = Totowa, NJ | veditors = Gerrard JA }}</ref>