A heat-sensitive gelling agent of animal origin, gelatin is used in molecular gastronomy for a vast array of dishes: entrees, pastries, confectionaries and even cocktails.
Gelatin is a protein food additive obtained by hydrolysis of collagen, the most common animal protein. Hydrolysis refers to any process using chemical denaturing through the use of water. The gelatin is traditionally used in dishes such as the French pot-au-feu, or the Portuguese cozido.
To produce gelatin industrially, bones and skin from pork or beef are mainly used although there is also fish gelatin. These are boiled in an acid (for pork and fish) or alkaline (for beef) solution, so as to solubilize and transform their collagen into gelatin. The fat is then removed from the gelatin solution, which is concentrated by evaporation, filtered, dried and powdered.
The byproducts of cattle used to produce gelatin are subject to the same standards of quality and safety as those applicable to the production and processing of meat. It has also repeatedly been scientifically proven that neurological diseases that have struck animals in recent years could not affect what was produced from their bones and hides.
The multiple properties of gelatin make it very versatile. It is part of the hydrocolloid family, substances which, in aqueous solution, impede the mobility of water and thus affect the texture. It is obviously a gelling agent and its product is thermo-reversible, that is to say, it melts under the effect of heat. The relative strength of gels formed by various gelatins is measured on a scale called "Bloom". Gelatin is also a thickening and a foaming agent. It allows the retention of water, stabilizes emulsions, or can form protective films.
The main property of gelatin is to form a thermo-reversible gel. In order to do this, it must first be dissolved in water at about 50°C (122°F). Gelling occurs when cooling at temperatures below 15°C (59°F). Unlike agar-agar gels, gelatin liquefies at a temperature of about 35°C (95°F), allowing it to melt quickly in the mouth, a much appreciated property during tasting.
The gelling properties may be offset by an excessive concentration of salts, acids or alcohol in the preparation. The gelatin should not be poured in a boiling solution because too much heat will destroy its properties. Neither should the gelatin preparation be frozen, because the thawed product will have lost its properties and become crumbly.
Gelatin has many uses. For example, it has been used as an emulsifier since the beginning of photography. The photographic film is indeed covered with a thin layer of silver halide crystals kept in suspension through gelatin. When the film is exposed to light, silver halide undergoes a chemical transformation and prints a latent image on the film that will be revealed during development. Pharmaceutical capsules are also made of gelatin. Gelatin is also found in low-fat margarine and is used as a stabilizer in stirred yogurt containing fruit, some cheeses and thickened cream. Moreover, it adds viscosity to dehydrated soups. Finally, it is used to clarify fruit juices and bind wines, because gelatin reacts with tannins to form a precipitate.
Creative cooking applications
Gelatin is popular in many meat dishes to which it provides smoothness, flavor and sheen. It is also used in a variety of other dishes: aspics, terrines, mousses, jellies. Desserts are certainly no exception: Bavarian cream, panna cotta, mousse, trifle, lustrous glazes and other fruity gelatin desserts. Several properties of gelatin are used in confectionery, as much in its home version as in the industrial version. The gelling properties are indeed being used to make jelly candies and its ability to stabilize foams allows the making of marshmallow. Adding 0.5% gelatin to an aqueous solution before freezing it allows the ice crystals to be much smaller than they would have been without gelatin. This property can make ice creams or popsicles much smoother.
Gelatin retains its properties in solutions of up to 40% alcohol. Gelatin can therefore be used to create cocktails with an original and surprising look and texture. Alcohol may be served in jelly bites that immediately melt in the mouth. When using gelatins that need to be heated, however, this requires close monitoring of temperatures to prevent the alcohol from evaporating.
In order to circumvent this problem, it recently became possible to obtain specially hydrolyzed gelatin that dissolves in a cold solution. The cold water soluble gelatin can thus cause immediate gel after it is dissolved in alcohol. No temperature control is required. However, in order to facilitate its dispersion, cold water soluble gelatin must first be mixed with about twice its volume of another soluble powder. Icing sugar is what is normally used.
Tips and tricks
Gelatin usually comes in sheets or in powder form. When gelatin is in sheet form, it must first be put in cold water so it can swell and hydrate. Water must then be squeezed out before gelatin can be mixed into the preparation. It will then melt to form a homogeneous solution when heated to 50°C (122°F). The hydrated and pressed sheet can also be melted in a microwave oven before it is added to the mixture. Powdered gelatin can generally be mixed straight into the hot water.
Some raw fruits contain proteolytic enzymes that break certain bonds in proteins. They therefore have the effect of destroying the gelling property of gelatin. Consequently, if one wishes to use gelatin with, for example, pineapple, papaya, kiwi, peach, mango, figs or guava, the fruit must first be briefly cooked through steaming or under hot water.