- Education and Science
Gelatin from Collagen - Facts, Foods and Uses
Gelatin or Gelatine
Gelatin (or gelatine) is a pale yellow, odorless and almost tasteless solid made by boiling collagen obtained from animals. Collagen is the most abundant protein in animal and human bodies and is found in connective tissue, which connects and supports other tissues. The collagen that's used for gelatin production is generally obtained from pig skin, cow skin or cow bones, but it’s sometimes obtained from the skin of fish instead. It isn't made from horns or from horse hooves, as is sometimes thought.
Gelatin is sold in a powder form or as sheets called leaves. When solid gelatin is added to hot water it dissolves to produce a solution. This solution thickens as it cools and eventually turns into a gel. Gelatin has many useful functions, including giving foods and cosmetics an appealing texture, improving the mouthfeel of foods and forming gel caps for medications. It's also used in a variety of crafts and in sports.
Gelatin and Special Diets
Gelatin is widely used in the food industry, but its addition to food creates problems for certain people. Some people object to the use of gelatin for religious or ethical reasons because it's produced from animal tissues or because it's made from the tissues of specific animals. Any product made from pig tissue is unacceptable in some religions. People with certain religious beliefs require animals to be killed in a particular way (ritual slaughter) before they will eat any product obtained from them. Vegetarians may also refuse to use products containing gelatin.
There are materials in plants which form gels and can be substituted for gelatin, but they have slightly different properties from real gelatin. Nevertheless, they are a good option for people who don't want to use a product obtained from animals. Two of these gelatin substitutes are agar and carrageenan.
How to Make Gelatin
Gelatin can be made at home by boiling animal skin and bones. The boiling process converts the collagen in the skin and bones into gelatin. The process of making gelatin in industry is similar, but additional steps are performed to improve the quality of the gelatin. The animal parts are first washed and degreased. They are then treated with an acidic or basic solution to remove minerals and make the collagen easier to access. Next, the processed animal parts are boiled in distilled water to produce gelatin. Finally, the water is evaporated from the liquid and the solid gelatin is pressed into sheets or ground into a powder.
If you boil beef bones at home to make stock, you'll probably notice a gel forming in the liquid as it cools. This is due to the production of gelatin from the collagen in the bones.
How to Make Beef Stock
Composition of Gelatin
Gelatin is a mixture of proteins and peptides obtained from the partial breakdown of collagen. A protein is a long chain of amino acids; a peptide is a shorter chain of amino acids.
Gelatin is rich in glycine and proline, two amino acids that are said to be "non-essential" because our bodies can make them. On the other hand, gelatin doesn't contain tryptophan and is very low in threonine, isoleucine and methionine. These four amino acids are said to be "essential" because we can't make them and must obtain them pre-formed in our diet.
Gelatin is a popular and useful food additive, but it’s not a very nutritious source of protein for humans because it lacks some of the essential amino acids.
Gelatin dissolves in hot water and swells in cold water as it forms a gel.
Properties and Behavior
Gelatin in water is a hydrophilic colloid. A colloid is a mixture in which the particles of a substance are dispersed through a continuous medium. The particles are bigger than those in a solution but are still small. They aren't visible to us, can't be filtered and don't settle to the bottom of the container. The word "hydrophilic" means that gelatin attracts water.
When gelatin is added to hot water, the bonds holding amino acid chains together break. These chains then move through the liquid, becoming tangled. As the water is cooled, new bonds form between the tangled chains. In some places the chains form a triple helix (three amino acid chains joined together and twisted into a spiral). Water is trapped in the spaces within the helices and tangles, forming a gel.
Gelatin and Fruit Dessert Recipe
Uses of Gelatin in Foods
The gel formed by gelatin in water is stable over a specific temperature range (which depends on the quality of the gelatin and its concentration) and breaks down when it's heated. The gels that are added to foods such as marshmallows break down at below body temperature. This means that when the food is eaten, it softens and collapses, creating a "melt in the mouth" sensation and releasing flavor trapped in the gel.
Gelatin is used to make gelatinous desserts, gummy candies and many yogurts as well as some marshmallows. It's also added to certain meats to prevent them from drying out and to give them an attractive glaze. In canned meats, gelatin absorbs juices released from the meats as they are processed under pressure. In pâtés, the gelatin helps to stabilize the emulsified fat.
Gelatin is also useful for its thickening, emulsifying, binding and adhesive properties. In addition, it's able to attract impurities and clarify fruit juices, wines and vinegar.
Consommé is concentrated and clarified stock. Like stock, it forms a gel as it cools due to the presence of gelatin.
How to Make Consommé
An aspic is a savory dish in which a gelatin gel made from a meat stock - or more commonly from a consommé - surrounds and encases meat. The meat stock is made by simmering animal bones, meat scraps and vegetables in water. These may all be roasted first to intensify their flavor. After the mixture has been simmered for a long time, the solids are filtered out to leave the liquid stock. The stock is cooled slightly so that it thickens and is then poured over meat in a mold. The stock may need added gelatin in order to gel, depending on the amount of bone that was added to the pot.
A colorless gelatin gel is often used in commercial aspics so that the meat inside is clearly visible. The gel can make it easier to cut the meat without causing it to disintegrate. The word "aspic" also refers to a dish in which a gelatin gel encases vegetables.
A Vegetable Aspic Recipe
Gelatin in Desserts
Gelatin is often added to low fat dairy products such as yogurt, ice cream and buttermilk in order to provide the sensation of eating fat. It may be added to some full fat products as well. The gelatin provides a smooth and creamy mouthfeel and the breakup of the gel in the mouth resembles fat melting. Gelatin in creams and whipped toppings help to stabilize their consistencies.
Fresh pineapple and papaya contain enzymes that prevent a gelatin gel from forming. The enzymes prevent the formation of the bonds needed to hold the amino acid chains together as the gelatin forms a gel. The enzyme mixture in pineapple is called bromelain and the enzyme in papaya is papain. Canned pineapple doesn't contain bromelain since the heat applied during the canning process destroys the enzymes.
Other foods that reportedly prevent the gel from forming include kiwi, figs, guava and ginger root. Any form of these foods that has been heated during pasteurization or another process should allow the gelatin gel to set, since the critical enzyme or enzymes will have been destroyed.
Mousse for Dessert
One of my favorite desserts in my childhood was a mousse that my mother made. The recipe was very simple. Jelly powder was mixed with water and evaporated milk and then whipped. The result was a dessert with a lovely taste and texture. The video below shows a variation of this recipe.
Jelly Mousse Recipe
Cosmetic and Pharmaceutical Uses of Gelatin
Gelatin may be used in skin creams and lotions, face masks, shampoos, hair conditioners, hair sprays, nail polishes and lipsticks. It's sometimes referred to as "hydrolyzed animal protein". The gelatin attracts moisture and thickens the products, given them a creamy texture.
Gelatin is also used to create hard and soft capsules to enclose medication and supplements. Hard capsules consist of two parts and are made when a stainless steel mold is dipped into a warm gelatin solution. The capsules are later filled with a medication. Soft capsules, also called softgels, consist of one part and are made from sheets of gelatin. They are filled with a medication as they are made.
Gelatin has been touted as a natural cure for weak nails and hair, arthritis pain, joint pain and osteoporosis. Some people claim that it's beneficial for weight loss and for recovery after exercise. At the present time there is little scientific evidence that gelatin has medicinal benefits, however. Nevertheless, some people report that they find it useful for joint problems.
The gelatine gels used in food and medicines become a liquid as they warm up and are said to be thermally reversible substances. Gelatin gels used in industry usually have chemicals added to them and are no longer thermally reversible.
Other Uses of Gelatin
Gelatin is a versatile medium in arts and crafts for both adults and children. It's also used in some fun and unexpected ways. Some popular items that can be made from gelatin include the following.
- plates for printing
- cake decorations
- suncatchers for hanging up in a window
- edible models for school projects
- gummy worms (by putting gelatin in straws and allowing it to set)
- air fresheners (after a scent is added)
- photographic emulsions for film and paper
- the shells of paintballs
Gelatin is also used to bind the ingredients together in match heads and is added to some types of sandpaper.
Gelatin is used by synchronized swimmers to hold their hair in place. The gelatin stays in the hair until it's washed with hot water. The process of creating the hair gel is sometimes known as "knoxing" after a popular brand of gelatin.
Safety Concerns - BSE Prions
Since gelatin is often made from cow tissue, there has been some concern that it can transmit the bovine spongiform encephalopathy (BSE) prion to humans. A prion is a piece of protein that has an abnormal form and causes disease. Prions cause other proteins to become altered in a domino effect.
BSE is sometimes known as "mad cow disease", since the prion affects the cow's brain, nervous system and behavior. The brain becomes filled with holes, resembling a sponge. When humans are exposed to the BSE prion they develop Creutzfeldt-Jakob disease, a neurodegenerative disease that is unfortunately always fatal.
The FDA (United States Food and Drug Administration) has concluded that it's safe to eat gelatin produced from cow tissue if certain conditions are met. The requirements are that cows have their heads, spines and spinal cords removed immediately after slaughter, that these tissues don't contaminate other parts of the cows' bodies, that the cows showed no obvious signs of neurological disease before being killed and that they didn't come from a herd that contained an animal proven to have BSE.
Pure gelatin is considered to be a safe substance for humans to eat and apply to their body. The dry powder can last for a long time. However, gelatin gels that are going to be eaten should be kept in the refrigerator and eaten soon because the gel is a good food source for bacteria. In addition, cosmetics containing gelatin should be used reasonably quickly. The lids of cosmetic containers should be kept on the containers to reduce the chance of contamination.
A Versatile Substance
Gelatin is a surprisingly versatile substance. Although some people object to its use because it's an animal product, others find it very useful. It's interesting that a protein found in connective tissue can change into such a different substance when it's boiled!
References - Bovine Spongiform Encephalopathy (BSE)
© 2012 Linda Crampton