Gelatin or gelatine (from Latin: gelatus meaning "stiff" or "frozen") is a translucent, colorless, flavorless food ingredient, derived from collagen taken from animal body parts. It is brittle when dry and gummy when moist. It may also be referred to as hydrolyzed collagen, collagen hydrolysate, gelatine hydrolysate, hydrolyzed gelatine, and collagen peptides after it has undergone hydrolysis. It is commonly used as a gelling agent in food, medications, drug and vitamin capsules, photographic films and papers, and cosmetics.
Substances containing gelatin or functioning in a similar way are called gelatinous substances. Gelatin is an irreversibly hydrolyzed form of collagen, wherein the hydrolysis reduces protein fibrils into smaller peptides; depending on the physical and chemical methods of denaturation, the molecular weight of the peptides falls within a broad range. Gelatin is in gelatin desserts; most gummy candy and marshmallows; and ice creams, dips, and yogurts. Gelatin for cooking comes as powder, granules, and sheets. Instant types can be added to the food as they are; others must soak in water beforehand.
Hydrolysis results in the reduction of collagen protein fibrils of about 300,000 Da into smaller peptides. Depending upon the process of hydrolysis, peptides will have broad molecular weight ranges associated with physical and chemical methods of denaturation.
Amino acid content
The amino acid content of hydrolyzed collagen is the same as collagen. Hydrolyzed collagen contains 19 amino acids, predominantly glycine, proline and hydroxyproline, which together represent around 50% of the total amino acid content.
|Proline, or hydroxyproline||25%|
|Other essential amino acids||16%|
|Other non-essential amino acids||12%|
Amino acid content
Hydrolyzed collagen contains 8 out of 9 essential amino acids, including glycine and arginine—two amino-acid precursors necessary for the biosynthesis of creatine. It contains no tryptophan and is deficient in isoleucine, threonine, and methionine.
The bioavailability of hydrolyzed collagen in mice was demonstrated in a 1999 study; orally administered 14C hydrolyzed collagen was digested and more than 90% absorbed within 6 hours, with measurable accumulation in cartilage and skin. A 2005 study in humans found hydrolyzed collagen absorbed as small peptides in the blood.
Effects on skin
Ingestion of hydrolyzed collagen may affect the skin by increasing the density of collagen fibrils and fibroblasts, thereby stimulating collagen production. It has been suggested, based on mouse and in vitro studies, that hydrolyzed collagen peptides have chemotactic properties on fibroblasts or an influence on growth of fibroblasts.
Joint and bone effects
Some clinical studies report that the oral ingestion of hydrolyzed collagen decreases joint pain, those with the most severe symptoms showing the most benefit. Beneficial action is likely due to hydrolyzed collagen accumulation in the cartilage and stimulated production of collagen by the chondrocytes, the cells of cartilage. Several studies have shown that a daily intake of hydrolyzed collagen increases bone mass density in rats. It seems that hydrolyzed collagen peptides stimulated differentiation and osteoblasts activity – the cells that build bone – over that of osteoclasts (cells that destroy bone).
However, other clinical trials have yielded mixed results. In 2011, the European Food Safety Authority Panel on Dietetic Products, Nutrition and Allergies concluded that "a cause and effect relationship has not been established between the consumption of collagen hydrolysate and maintenance of joints". Four other studies reported benefit with no side effects; however, the studies were not extensive, and all recommended further controlled study. One study found that oral collagen only improved symptoms in a minority of patients and reported nausea as a side effect. Another study reported no improvement in disease activity in patients with rheumatoid arthritis. Another study found that collagen treatment may actually cause an exacerbation of rheumatoid arthritis symptoms.
Hydrolyzed collagen, like gelatin, is made from animal by-products from the meat industry, including skin, bones, and connective tissue.
In 1997, the U.S. Food and Drug Administration (FDA), with support from the TSE (transmissible spongiform encephalopathy) Advisory Committee, began monitoring the potential risk of transmitting animal diseases, especially bovine spongiform encephalopathy (BSE), commonly known as mad cow disease. An FDA study from that year stated: "...steps such as heat, alkaline treatment, and filtration could be effective in reducing the level of contaminating TSE agents; however, scientific evidence is insufficient at this time to demonstrate that these treatments would effectively remove the BSE infectious agent if present in the source material." On March 18, 2016 the FDA finalized three previously-issued interim final rules designed to further reduce the potential risk of BSE in human food. The final rule clarified that "gelatin is not considered a prohibited cattle material if it is manufactured using the customary industry processes specified."
In 2006, the European Food Safety Authority stated that the SSC opinion was confirmed, that the BSE risk of bone-derived gelatin was small, and that it recommended removal of the 2003 request to exclude the skull, brain, and vertebrae of bovine origin older than 12 months from the material used in gelatin manufacturing.
In cosmetics, hydrolyzed collagen may be found in topical creams, acting as a product texture conditioner, and moisturizer. Collagen implants or dermal fillers are also used to address the appearance of wrinkles, contour deficiencies, and acne scars, among others. The U.S. Food and Drug Administration has approved its use, and identifies cow (bovine) and human cells as the sources of these fillers. According to the FDA, the desired effects can last for 3-4 months, which is relatively the most short-lived compared to other materials used for the same purpose.
Composition and properties
Gelatin is a mixture of peptides and proteins produced by partial hydrolysis of collagen extracted from the skin, bones, and connective tissues of animals such as domesticated cattle, chicken, pigs, and fish. During hydrolysis, the natural molecular bonds between individual collagen strands are broken down into a form that rearranges more easily. Its chemical composition is, in many aspects, closely similar to that of its parent collagen. Photographic and pharmaceutical grades of gelatin generally are sourced from cattle bones and pig skin. Gelatin has proline, hydroxyproline and glycine in its polypeptide chain. Glycine is responsible for close packing of the chains. Presence of proline restricts the conformation. This is important for gelation properties of gelatin.
Gelatin readily dissolves in hot water and sets to a gel on cooling. When added directly to cold water, it does not dissolve well, however. Gelatin also is soluble in most polar solvents. Gelatin solutions show viscoelastic flow and streaming birefringence. Solubility is determined by the method of manufacture. Typically, gelatin can be dispersed in a relatively concentrated acid. Such dispersions are stable for 10–15 days with little or no chemical changes and are suitable for coating purposes or for extrusion into a precipitating bath.
The mechanical properties of gelatin gels are very sensitive to temperature variations, the previous thermal history of the gels, and the amount of time elapsing. These gels exist over only a small temperature range, the upper limit being the melting point of the gel, which depends on gelatin grade and concentration, but typically, is less than 35 °C (95 °F) and the lower limit the freezing point at which ice crystallizes. The upper melting point is below human body temperature, a factor that is important for mouthfeel of foods produced with gelatin. The viscosity of the gelatin-water mixture is greatest when the gelatin concentration is high and the mixture is kept cool at about 4 °C (39 °F). The gel strength is quantified using the Bloom test. Gelatin's strength (but not viscosity) declines if it is subjected to temperatures above 100 °C (212 °F), or if it is held at temperatures near 100 °C for an extended period of time.
The worldwide production amount of gelatin is about 375,000–400,000 tonnes per year (830×106–880×106 lb/a). On a commercial scale, gelatin is made from by-products of the meat and leather industries. Most gelatin is derived from pork skins, pork and cattle bones, or split cattle hides. Gelatin made from fish by-products avoids some of the religious objections to gelatin consumption. The raw materials are prepared by different curing, acid, and alkali processes that are employed to extract the dried collagen hydrolysate. These processes may take several weeks, and differences in such processes have great effects on the properties of the final gelatin products.
Gelatin also can be prepared at home. Boiling certain cartilaginous cuts of meat or bones results in gelatin being dissolved into the water. Depending on the concentration, the resulting stock (when cooled) will form a jelly or gel naturally. This process is used for aspic.
While many processes exist whereby collagen may be converted to gelatin, they all have several factors in common. The intermolecular and intramolecular bonds that stabilize insoluble collagen must be broken, and also, the hydrogen bonds that stabilize the collagen helix must be broken. The manufacturing processes of gelatin consists of several main stages:
- Pretreatments to make the raw materials ready for the main extraction step and to remove impurities that may have negative effects on physicochemical properties of the final gelatin product.
- Hydrolysis of collagen into gelatin.
- Extraction of gelatin from the hydrolysis mixture, which usually is done with hot water or dilute acid solutions as a multistage process.
- The refining and recovering treatments including filtration, clarification, evaporation, sterilization, drying, rutting, grinding, and sifting to remove the water from the gelatin solution, to blend the gelatin extracted, and to obtain dried, blended, ground final product.
If the raw material used in the production of the gelatin is derived from bones, dilute acid solutions are used to remove calcium and other salts. Hot water or several solvents may be used to reduce the fat content, which should not exceed 1% before the main extraction step. If the raw material consists of hides and skin; size reduction, washing, removal of hair from hides, and degreasing are necessary to prepare the hides and skins for the hydrolysis step.
After preparation of the raw material, i.e., removing some of the impurities such as fat and salts, partially purified collagen is converted into gelatin through hydrolysis. Collagen hydrolysis is performed by one of three different methods: acid-, alkali-, and enzymatic hydrolysis. Acid treatment is especially suitable for less fully cross-linked materials such as pig skin collagen and normally requires 10 to 48 hours. Alkali treatment is suitable for more complex collagen such as that found in bovine hides and requires more time, normally several weeks. The purpose of the alkali treatment is to destroy certain chemical crosslinks still present in collagen. Within the gelatin industry, the gelatin obtained from acid-treated raw material has been called type-A gelatin and the gelatin obtained from alkali-treated raw material is referred to as type-B gelatin.
Advances are occurring to optimize the yield of gelatin using enzymatic hydrolysis of collagen. The treatment time is shorter than that required for alkali treatment, and results in almost complete conversion to the pure product. The physical properties of the final gelatin product are considered better.
Extraction is performed with either water or acid solutions at appropriate temperatures. All industrial processes are based on neutral or acid pH values because although alkali treatments speed up conversion, they also promote degradation processes. Acidic extraction conditions are extensively used in the industry, but the degree of acid varies with different processes. This extraction step is a multistage process, and the extraction temperature usually is increased in later extraction steps, which ensures minimum thermal degradation of the extracted gelatin.
This process includes several steps such as filtration, evaporation, drying, grinding, and sifting. These operations are concentration-dependent and also dependent on the particular gelatin used. Gelatin degradation should be avoided and minimized, so the lowest temperature possible is used for the recovery process. Most recoveries are rapid, with all of the processes being done in several stages to avoid extensive deterioration of the peptide structure. A deteriorated peptide structure would result in a low gel strength, which is not generally desired.
Early history of food applications
The first use of gelatin in foods is attributed to medieval Britain (1400s) when cattle hooves were boiled to produce a gel. Further commercial development occurred in 1754 when a British manufacturing patent was issued. Food applications in France and the United States during 1800–1900 appear to have established the versatility of gelatin, including the origin of its popularity in the US as Jell-O. Over middle-late 1800s, Charles and Rose Knox of New York manufactured and marketed gelatin powder, diversifying the appeal and applications of gelatin.
Probably best known as a gelling agent in cooking, different types and grades of gelatin are used in a wide range of food and nonfood products. Common examples of foods that contain gelatin are gelatin desserts, trifles, aspic, marshmallows, candy corn, and confections such as Peeps, gummy bears, fruit snacks, and jelly babies. Gelatin may be used as a stabilizer, thickener, or texturizer in foods such as yogurt, cream cheese, and margarine; it is used, as well, in fat-reduced foods to simulate the mouthfeel of fat and to create volume. It also is used in the production of several types of Chinese soup dumplings, specifically Shanghainese soup dumplings, or xiaolongbao, as well as Shengjian mantou, a type of fried and steamed dumpling. The fillings of both are made by combining ground pork with gelatin cubes, and in the process of cooking, the gelatin melts, creating a soupy interior with a characteristic gelatinous stickiness.
Gelatin is used for the clarification of juices, such as apple juice, and of vinegar.
Isinglass is obtained from the swim bladders of fish. It is used as a fining agent for wine and beer. Besides hartshorn jelly, from deer antlers (hence the name "hartshorn"), isinglass was one of the oldest sources of gelatin.
- Certain professional and theatrical lighting equipment use color gels to change the beam color. Historically, these were made with gelatin, hence the term, color gel.
- Gelatin typically constitutes the shells of drug and vitamin capsules to make them easier to swallow. Hypromellose is a vegetarian-acceptable alternative to gelatin, but is more expensive to produce.
- Some animal glues such as hide glue may be unrefined gelatin.
- It is used to hold silver halide crystals in an emulsion in virtually all photographic films and photographic papers. Despite significant effort, no suitable substitutes with the stability and low cost of gelatin have been found.
- Used as a carrier, coating, or separating agent for other substances, for example, it makes β-carotene water-soluble, thus imparting a yellow color to any soft drinks containing β-carotene.
- Ballistic gelatin is used to test and measure the performance of bullets shot from firearms.
- Gelatin is used as a binder in match heads and sandpaper.
- Cosmetics may contain a non-gelling variant of gelatin under the name hydrolyzed collagen (hydrolysate).
- Gelatin was first used as an external surface sizing for paper in 1337 and continued as a dominant sizing agent of all European papers through the mid-nineteenth century. In modern times, it is mostly found in watercolor paper, and occasionally in glossy printing papers, artistic papers, and playing cards. It maintains the wrinkles in crêpe paper.
Dietary restrictions and gelatin substitutes
The consumption of gelatin from particular animals may be forbidden by religious rules or cultural taboos. For example, Jewish kosher and Islamic halal customs require gelatin from sources other than pigs, such as cattle (that have been slaughtered according to the religious regulations) or fish (that they are allowed to consume). Roma people are cautious of gelatin products that may have been made from horses, as their culture forbids the consumption of horses. Some companies specify the source of the gelatin used.
Vegans and vegetarians do not eat foods containing gelatin made from animals. Likewise, Sikh, Hindu, and Jain customs may require gelatin alternatives from sources other than animals, as many Hindus, most Jains and some Sikhs are vegetarian. Partial alternatives to gelatins derived from animals include the seaweed extracts agar and carrageenan, and the plant extracts pectin and konjac.
In 2011, the European Food Safety Authority Panel on Dietetic Products, Nutrition, and Allergies concluded that "a cause and effect relationship has not been established between the consumption of collagen hydrolysate and maintenance of joints". A 2012 review also found insufficient evidence to support its use for osteoarthritis. By contrast, in 2013, Health Canada approved a label for "hydrolyzed collagen", specifying that the label may make a health claim that supplemental dietary amino acid intake from hydrolyzed collagen "helps to reduce joint pain associated with osteoarthritis".
- Collagen Hybridizing Peptide, a peptide that can bind and stain denatured collagen in tissues
- Kodjo Boady Djagnya; Zhang Wang; Shiying Xu (2010). "Gelatin: A Valuable Protein for Food and Pharmaceutical Industries: Review". Critical Reviews in Food Science and Nutrition. 41 (6): 481–492. doi:10.1080/20014091091904. PMID 11592686.
- Bensaid, A.; Tomé, D.; L’Heureux-Bourdon, D.; Even, P.; Gietzen, D.; Morens, C.; Gaudichon, C.; Larue-Achagiotis, C.; Fromentin, G. (2003). "A high-protein diet enhances satiety without conditioned taste aversion in the rat". Physiology and Behavior. 78 (2): 311–320. doi:10.1016/S0031-9384(02)00977-0. PMID 12576130.
- Fricke, O.; Baecker, N.; Heer, M.; Tutlewski, B.; Schoenau, E. (2008). "The effect of L-arginine administration on muscle force and power in postmenopausal women". Clinical Physiology and Functional Imaging. 28 (5): 307–311. doi:10.1111/j.1475-097X.2008.00809.x. PMID 18510549.
- Oesser, S.; Adam, M.; Babel, W.; Seifert, J. (1999). "Oral administration of 14C labelled gelatine hydrolysate leads to an accumulation of radioactivity in cartilage of mice (C57/BL)". Journal of Nutrition. 129 (10): 1891–1895. doi:10.1093/jn/129.10.1891. PMID 10498764.
- Iwai, K.; Hasegawa, T.; Taguchi, Y.; Morimatsu, F.; Sato, K.; Nakamura, Y.; Higashi, A.; Kido, Y.; Nakabo, Y.; Ohtsuki, K. (2005). "Identification of food-derived collagen peptides in human blood after oral ingestion of gelatine hydrolysates". Journal of Agricultural and Food Chemistry. 53 (16): 6531–6536. doi:10.1021/jf050206p. PMID 16076145.
- Matsuda, N.; Koyama, Y.; Hosaka, Y.; Ueda, H.; Watanabe, T.; Araya, T.; Irie, S.; Takehana, K (2006). "Effects of ingestion of collagen peptide on collagen fibrils and glycosaminoglycans in the dermis". Journal of Nutritional Science and Vitaminology. 52 (3): 211–215. doi:10.3177/jnsv.52.211. PMID 16967766.
- Postlethwaite, A. E.; Seyer, J. M.; Kang, A. H. (1978). "Chemotactic attraction of human fibroblasts to type I, II, and III collagens and collagen-derived peptides". Proceedings of the National Academy of Sciences of the United States of America. 75 (2): 871–875. Bibcode:1978PNAS...75..871P. doi:10.1073/pnas.75.2.871. PMC 411359. PMID 204938.
- Shigemura, Y.; K Iwai; F Morimatsu; T Iwamoto; T Mori; C Oda; T Taira; EY Park; Y Nakamura; K Sato (2009). "Effect of prolyl-hydroxyproline (Pro-Hyp), a food-derived collagen peptide in human blood, on growth of fibroblasts from mouse skin". Journal of Agricultural and Food Chemistry. 57 (2): 444–449. doi:10.1021/jf802785h. PMID 19128041.
- Moskowitz, R. (2000). "Role of collagen hydrolysate in bone and joint disease". Seminars in Arthritis and Rheumatism. 30 (2): 87–99. doi:10.1053/sarh.2000.9622. PMID 11071580.
- Ruiz-Benito, P.; Camacho-Zambrano, M.M.; Carrillo-Arcentales, J.N.; Mestanza-Peralta, M.A.; Vallejo-Flores, C.A.; Vargas-Lopez, S.V.; Villacis-Tamayo, R.A.; Zurita-Gavilanes, L.A. (2009). "A randomized controlled trial on the efficacy and safety of a food ingredient, collagen hydrolysate, for improving joint comfort". International Journal of Food Sciences and Nutrition. 12: 1–15. doi:10.1080/09637480802498820. PMID 19212858.
- Oesser, S.; Seifert, J. (2003). "Stimulation of type II collagen biosynthesis and secretion in bovine chondrocytes cultured with degraded collagen". Cell and Tissue Research. 311 (3): 393–399. doi:10.1007/s00441-003-0702-8. PMID 12658447.
- Nomura, Y.; Oohashi, K.; Watanabe, M. and Kasugai (2005). "Increase in bone mineral density through oral administration of shark gelatine to ovariectomized rats". Nutrition. 21 (11–12): 1120–1126. doi:10.1016/j.nut.2005.03.007. PMID 16308135.
- Wu, J.; Fujioka, M.; Sugimoto, K.; Mu, G.; Ishimi, Y (2004). "Increase of effectiveness of oral administration of collagen peptide on bone metabolism in growing and mature rats". Bone and Mineral Metabolism. 22 (6): 547–553. doi:10.1007/s00774-004-0522-2. PMID 15490264.
- European Food Safety Authority - EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on the substantiation of a health claim related to collagen hydrolysate and maintenance of joints pursuant to Article 13(5) of Regulation (EC) No 1924/20061. EFSA Journal 2011;9(7):2291.
- Barnett ML, Kremer JM, St Clair EW, Clegg DO, Furst D, Weisman M, Fletcher MJ, Chasan-Taber S, Finger E, Morales A, Le CH, Trentham DE: Treatment of rheumatoid arthritis with oral type II collagen. Results of a multicenter, double-blind, placebo-controlled trial. Arthritis Rheum 1998 Feb;41(2):290-7.
- Ausar SF, Beltramo DM, Castagna LF, Quintana S, Silvera E, Kalayan G, Revigliono M, Landa CA, Bianco ID: Treatment of rheumatoid arthritis by oral administration of bovine tracheal type II collagen. Rheumatol Int. 2001 May;20(4):138-44.
- Trentham DE, Dynesius-Trentham RA, Orav EJ, Combitchi D, Lorenzo C, Sewell KL, Hafler DA, Weiner HL: Effects of oral administration of type II collagen on rheumatoid arthritis. Science 1993 Sep 24;261(5129):1727-30.
- Bagchi D, Misner B, Bagchi M, Kothari SC, Downs BW, Fafard RD, Preuss HG: Effects of orally administered undenatured type II collagen against arthritic inflammatory disease: a mechanistic exploration. Int J Clin Pharmacol Res. 2002;22(3-4):101-10.
- Sieper J, Kary S, Sorensen H, Alten R, Eggens U, Huge W, Hiepe F, Kuhne A, Listing J, Ulbrich N, Braun J, Zink A, Mitchison NA: Oral type II collagen treatment in early rheumatoid arthritis. A double-blind, placebo-controlled, randomized trial. Arthritis Rheum. 1996 Jan;39(1):41-51.
- McKown KM, Carbone LD, Kaplan SB, Aelion JA, Lohr KM, Cremer MA, Bustillo J, Gonzalez M, Kaeley G, Steere EL, Somes GW, Myers LK, Seyer JM, Kang AH, Postlethwaite AE: Lack of efficacy of oral bovine type II collagen added to existing therapy in rheumatoid arthritis. Arthritis Rheum. 1999 Jun;42(6):1304-8
- Cazzola M, Antivalle M, Sarzi-Puttini P, Dell’Acqua D, Panni B, Caruso I: Oral type II collagen in the treatment of rheumatoid arthritis. A six-month double blind placebo-controlled study. Clin Exp Rheumatol. 2000 Sep-Oct; 18(5):571-7.
- Helps to reduce joint pain associated with osteoarthritis (Bruyère et al. 2012; Benito-Ruiz et al. 2009; Clark et al. 2008).
- U.S. Food and Drug Administration. "The Sourcing and Processing of Gelatin to Reduce the Potential Risk Posed by Bovine Spongiform Encephalopathy (BSE) in FDA-Regulated Products for Human Use". Archived from the original on 21 January 2017.
- Food and Drug Administration (18 March 2016). "Federal Register :: Use of Materials Derived From Cattle in Human Food and Cosmetics". Federal Register, The Daily Journal of the United States Government. Archived from the original on 3 June 2017. Retrieved 24 May 2017.
- U.S. Food and Drug Administration (17 March 2016). "FDA Announces Final Rule on Bovine Spongiform Encephalopathy". Archived from the original on 30 April 2017. Retrieved 24 May 2017.
Finally, the rule provides a definition of gelatin and clarifies that gelatin is not considered a prohibited cattle material if it is manufactured using the customary industry processes specified. Gelatin was never considered a prohibited cattle material, but FDA had never specifically defined gelatin in past IFRs.
- Scientific Steering Committee, European Union (6–7 March 2003). "Updated Opinion On The Safety With Regard To TSE Risks Of Gelatine Derived From Ruminant Bones or Hides" (PDF). Archived from the original (PDF) on 26 October 2012.
- Gelatine Manufacturers of Europe (GME) (June 2003). "The Removal and Inactivation of Potential TSE Infectivity by the Different Gelatin Manufacturing Processes" (PDF). Archived (PDF) from the original on 14 January 2012.
- Scientific Panel on Biological Hazards of the European Food Safety Authority (EFSA) (2006). "Quantitative assessment of the human BSE risk posed by gelatine with respect to residual BSE risk". EFSA Journal. 312: 1–29. doi:10.2903/j.efsa.2006.312.
- Health, Center for Devices and Radiological (13 June 2019). "Dermal Fillers Approved by the Center for Devices and Radiological Health". FDA.
- Ward, A.G.; Courts, A. (1977). The Science and Technology of Gelatin. New York: Academic Press. ISBN 978-0-12-735050-9.
- "Gelatin Handbook" (PDF). Archived (PDF) from the original on 16 May 2017. Retrieved 27 September 2017.
- "Handbook of Gelatin" (PDF). Archived (PDF) from the original on 16 May 2017. Retrieved 27 September 2017.
- Francis, Frederick J., ed. (2000). "Gelatin". Encyclopedia of Food Science and Technology (2nd ed.). John Wiley & Sons. pp. 1183–1188. ISBN 9780471192558. Archived from the original on 29 August 2005.
- 6 Unexpected Factors That Can Ruin Your Gelatin Desserts | Serious Eats
- The Science of Gelatin - FineCooking
- "Global Gelatin market". Archived from the original on 5 June 2016. Retrieved 11 May 2016.
- "Natural Health Products Ingredients Database: Hydrolyzed Collagen". Government of Canada, Health Canada, Health Products and Food Branch, Natural Health Products Directorate. 12 June 2013. Archived from the original on 12 May 2016. Retrieved 9 May 2016.
- "Type A & B Process Definition". Vyse Gelatin Company. 26 October 2009. Archived from the original on 1 March 2015. Retrieved 16 July 2014.
- Ahmad, Tanbir; Ismail, Amin; Ahmad, Siti Aqlima; Khalil, Khalilah A.; Kumar, Yogesh; Adeyemi, Kazeem D.; Sazili, Awis Q. (February 2017). "Recent advances on the role of process variables affecting gelatin yield and characteristics with special reference to enzymatic extraction: A review". Food Hydrocolloids. 63: 85–96. doi:10.1016/j.foodhyd.2016.08.007.
- "Gelatin". Encyclopedia.com. 2016. Archived from the original on 17 September 2016. Retrieved 9 September 2016.
- Wyman, Carolyn (2001). Jell-o: A Biography: the History And Mystery of America's Most Famous Dessert. Diane Publishing Company. ISBN 978-0756788544.
- "Gelatin: background". Encyclopedia.com. 2016. Archived from the original on 17 September 2016. Retrieved 9 September 2016.
- "National Organic Standards Board Technical Advisory Panel Review: Gelatin processing" (PDF). omri.org. Archived from the original (PDF) on 27 September 2007.
- Finch, C. A.; Ramachandran, Srinivasa (1983). Matchmaking, science, technology, and manufacture. Ellis Horwood. p. 141. ISBN 9780853123156.
- Packham, D. E. (8 February 2006). Handbook of Adhesion. John Wiley & Sons. p. 48. ISBN 9780470014219.
- Thurn, Jim. "History, Chemistry, and Long Term Effects of Alum-Rosin Size in Paper". ischool.utexas.edu. Archived from the original on 25 April 2012.
- European Food Safety Authority, Panel on Dietetic Products, Nutrition and Allergies (2011). "Scientific Opinion on the substantiation of a health claim related to collagen hydrolysate and maintenance of joints pursuant to Article 13(5) of Regulation (EC) No 1924/20061". EFSA Journal. 9 (7): 2291. doi:10.2903/j.efsa.2011.2291.CS1 maint: multiple names: authors list (link)
- Van Vijven, JP; Luijsterburg, PA; Verhagen, AP; van Osch, GJ; Kloppenburg, M; Bierma-Zeinstra, SM (August 2012). "Symptomatic and chondroprotective treatment with collagen derivatives in osteoarthritis: a systematic review". Osteoarthritis and Cartilage. 20 (8): 809–21. doi:10.1016/j.joca.2012.04.008. PMID 22521757.