Gelling with Gelatin

Gelatin – a fairly old ingredient for setting many items and cooking is also spelt as gelatine and originates f r o m the French term, gélatine.  It is a transluscent brittle substance, colourless or light yellow.  In itself it has no taste or odour and it is created by prolonged boiling of connective tissue of animals such as skin, cartilege, and bones. Apart f r o m its use in food, it is also of use in the pharmaceutical, cosmetic and photography industry. Technically also known as E number E441, it is an irreversibly hudrolyzed form of collagen.
Substances containing gelatin or functioning in a similar way are called gelatinous. Apart f r o m culinary use, gelatin is also used in the pharmaceutical and makeup industry. Gelatin melts to a liquid when heated and solidifies when cooled again. Together with water, it forms a semi-solid colloid gel. Gelatin forms a solution of high viscosity in water, which sets to a gel on cooling, and its chemical composition is, in many respects, closely similar to that of its parent collagen.
Gelatin is also soluble in most polar solvents. Gelatin 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 and the lower limit, the freezing point at which ice crystallizes. The mechanical properties are very sensitive to temperature variations, previous thermal history of the gel, and time. The viscosity of the gelatin/water mixture increases with concentration and when kept cool. In addition to the animal gelatins described above, there are also vegetarian gelatins such as agar.

Gelatin in Food

Household gelatin comes in the form of sheets, granules or as powder. Instant types can be added to the food as they are; others need to be soaked in water beforehand. While the granular form of gelatin is easily available, the sheets are often sold only in large packaging making it suitable only for commercial users.
Special kinds of gelatin are made only f r o m certain animals or f r o m fish. In order to comply with food needs of the Jews and Muslims. Kosher (for the Jews) gelatin can be made with fish bones, and/or beef skins.  Unlike other restrictions it is considered kosher to use it with dairy products.  Kosher law is complex and the bones and hides used in gelatin production are considered ‘pareve’.  It means foods that are neither milk nor meat.  Some people assume this to mean that the product is ‘vegetarian’.  
To quote f r o m an article in Kashrus Magazine, on the issue: “since the gelatin product is f r o m hides or bones - not real flesh - and has undergone such significant changes, it is no longer considered ‘fleishig’ (meat) but ‘pareve’, and can be eaten with dairy products.”
Similarly when it says ‘halal gelatin’ it means the appropriate animals have been killed in mandatory manner and no pork products have been used in the making of gelatin.

Food uses

Common examples of foods that contain gelatin are desserts, jelly, trifles, marshmallows and confectioneries such as gummy bears. It may be used as a stabiliser, thickener, or texturizer in foods such as ice creams, jams, yogurt, cream cheese, margarine.  It is used, as well, in fat-reduced foods to simulate the mouth feel of fat and to create volume without adding calories.
Gelatin is used for the clarification of juices, such as apple juice, and of vinegar. It might come as a surprise that Isinglass, f r o m the swim bladders of fish, is still in use as a fining agent for wine and beer. Beside hartshorn jelly, f r o m deer antlers (hence the name “hartshorn”), isinglass was one of the oldest sources of gelatin.

Extraction & Recovery

After preparation of the raw material, i.e., reducing cross linkages between collagen components and removing some of the impurities such as fat and salts, partially purified collagen is converted into gelatin by extraction with either water or acid solutions at appropriate temperatures. All industrial processes are based on neutral or acid pH values because though alkali treatments speed up conversion, they also promote degradation processes. Acid extract conditions are extensively used in the industry but the degree of acid varies with different processes. This extraction step is a multi stage process, and the extraction temperature is usually increased in later extraction steps. This procedure ensures the minimum thermal degradation of the extracted gelatin.
Recovery 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 therefore 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 gelling strength, which is not generally desired.

Vegetarian Gelatin

For the strict vegetarian and vegans, gelatin may be substituted with similar gelling agents such as agar, natural gum, carrageenan, pectin or konnyaku.  These are sometimes referred to as “vegetable gelatins” although there is no chemical relationship; they are technically carbohydrates, not proteins. The name “gelatin” is colloquially applied to all types of gels and jellies; but properly used, it currently refers solely to the animal protein product. There is no vegetable source for gelatin. However, in respect to dietery requirements of segments of society, the gelatin suitable for vegetarians may be used for same effect in the product.
Some gelatinous desserts can be made with agar instead of gelatin, allowing them to congeal more quickly and at higher temperatures. Agar, a vegetable product made f r o m seaweed, is used especially in quick jelly powder mix and Asian jelly deserts, but also as an alternative that is acceptable to increasing number of vegetarians. Agar is more closely related to pectin and other gelling plant carbohydrates than to gelatin.
Another vegan alternative to gelatin is carageenan. This alternative sets more firmly than agar, and is often used in Jewish kosher cooking. Though it, too, is a type of seaweed, it tends not to have an unpleasant smell during cooking as agar sometimes does.

Technical Aspect

Although gelatin is 98–99% protein by dry weight, it has less nutritional value than many other protein sources. Gelatin is unusually high in the non-essential amino acids (i.e., those produced by the human body), while lacking certain other essential amino acids (i.e., those not produced by the human body). 
It contains no tryptophan and is deficient in methionine and threonine. Its other values and ratios of chemicals vary, especially the minor constituents, depending on the source of the raw material and processing technique. 
Gelatin is one of the few foods that cause a net loss of protein if eaten exclusively. Several people died of malnutrition in the 1970s while on popular ‘liquid protein’ diets.
For decades, gelatin has been touted as a good source of protein. It has also been said to strengthen nails and hair. However, there is little scientific evidence to support such an assertion, one which may be traced back to Knox’s revolutionary marketing techniques of the 1890s, when it was advertised that gelatin contains protein and that lack of protein causes dry, deformed nails. In fact, the human body itself produces abundant amounts of the proteins found in gelatin. Furthermore, dry nails are usually due to a lack of moisture, not protein.

Gelatin Production

The production of gelatin typically starts with the boiling of cattle bones or pig skins; contrary to popular conception, horns and hooves are not used. This material is then soaked with acid or alkali in large vats to extract and hydrolyze the protein collagen. The extract is then dried and ground to form a powder.
To make gelatin desserts, typically powdered gelatin is mixed with sugar and additives and artificial flavorings and food colours are added. Very hot water is added to swell the powdered gelatin and gel the liquid. The dessert gels slowly as it cools.
Because the collagen is processed extensively, the final product is not categorized as a meat or indeed animal product by the US federal government.
Eating tainted beef may have led to variant (CJD) in humans, but there are no known cases of variant CJD transmitted through collagen products such as gelatin.

Granular V/s Sheet Gelatin

When using the powdered form of gelatin follow following steps:
• Sprinkle the granules of gelatin over the surface cold water or liquid. Use 1/4 cup, 60ml, or whatever quantity is called for in the recipe, per envelope. Do not dump them in a pile, as the granules in the middle won’t dissolve.
• Let stand for 5 to 10 minutes.
• Add warm liquid or heat gently, stirring until dissolved. To verify the granules are melted, lift the stirring utensil and make certain that there are no undissolved granules clinging to it.
For the Sheet gelatin use follow suggested steps:
• Soak sheet(s) of gelatin in a bowl cold water for 5 to 10 minutes. (Figure about 1 cup, 250ml, cold water per sheet.)
• Once soft, lift sheets f r o m the cold water.
• Wring gently to remove excess water, than add to warm liquid, the quantity called for in the recipe, stirring until dissolved. If adding to a cold mixture, melt the softened sheets in a saucepan or microwave over very low heat, stirring just until melted completely. Then stir in the cold mixture gradually.

Diverse Uses & Tips on Gelatin

• Gelatin may be used by swimmers to hold their hair in place during performances in water as it will not dissolve in the cold water of the pool.  
• If added to boiling water and cooled, unflavoured gelatin makes a good home made hair styling gel that is cheaper than commercial products but it has a short shelf life.  
• Blocks of ballistic gelatin simulate mjuscle tissue as a standardised medium for testing firearms ammunition.
• It is also used as a biological substrate to culture adherent cells. 
• Certain professional and theatrical lighting equipment use colour gels to change the beam colour. These used to be made with gelatin, hence the term colour gel.
• Blocks of ballistic gelatin simulate muscle tissue as a standardized medium for testing firearms ammunition.
• Both sheet and powdered gelatin should be dissolved in cold water. If hot water is used, granules of gelatin will swell on the outside too quickly, preventing the water f r o m getting in to the center. 
• Don’t boil things made with gelatin. That can make the gelatin lose its efficacy.
• Desserts made with gelatin should chill for at least eight hours, but twenty four hours is best. After twenty four hours, gelatin will not set any further.
• Some people prefer to use sheet gelatin, claiming it has no odour and the gel sets finer. Another advantage is no chance of un-dissolved granules when using sheet gelatin.
• If you want something made with gelatin to set faster, chill the mold or container first. Also you can stir the mixture constantly in a metal bowl placed in an ice bath until it begins to set, then pour it into the mold or container.
• Gelatin lasts forever according to American claim. If the packet gives an expiration date, it has to do with a “degradation of the packaging”.
• Certain tropical fruits, such as pineapple, kiwifruit, and ginger, have an enzyme (bromelin) that can prevent gelatin for setting. Heating the fruit completely through before using will destroy the enzyme.
• Some folks add gelatin to sorbets to keep them soften when frozen. If so, for 1 quart (1l) of mixture, dissolve 1 teaspoon of gelatin in 2 tablespoons or so of the cold sorbet mixture and let soften for 5 minutes. Warm a small amount of the sorbet mixture and pour it into the gelatin, stirring until dissolved, then mix the gelatin back into the sorbet mixture before churning.

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