Gelification is defined as the formation of gel in a process where a liquid substance is turned solid. The process of gelation occurs when macromolecules associate with each other and are bound with water. Properties of the solidified matter can range anywhere from soft and fragile to firm and molded.
In the realm of classic cuisine, gelatins are a basic component that carries a distinct attribute: these substances are heat sensitive and turn to a viscous liquid with exposure to high temperatures. Upon cooling, these regain their original solid form.
Jelly and other gelatin based dishes have long been part of culinary preparations. The use of animal gels dates back to earlier days in western countries. On the other hand, the use of plant based gels can be traced back to early Asian cooking tradition.
Gelatins have undergone a notable evolution with modern cooking due to their versatile nature. Under the science of cooking otherwise known as molecular gastronomy, gelification is one of the basic techniques used. The culinary innovation of this age old preparation has lead to the intense flavors and unique dining experiences.
In the world of modern cooking, Gelification plays a wide role. Its main purpose is to provide texture to liquids by turning these into gels through the use of a thickening agent. Many of the gelling agents used do not have any flavor or color, making these ideal food additives since they do not affect flavor. As a matter of fact, certain gelling agents may even enhance the flavor of food in the mouth by causing it to more fully coat the tongue.
In many cases the firmness of the gelling agents allow for the creation of unique shapes and consistency for food, especially with the use of agar agar. Liquids can be turned into balls, sheets, noodles and more.
In terms of texture the various gelling substances also allow dishes to be made with smoothness. Such is possible for all types of food ranging from appetizers to desserts.
Many times gelification also offers a way to present cuisine differently. Thanks to the unique properties of the different gelling substances it becomes possible to serve dishes which may be unorthodox. For example, jelly which is commonly served cold may be served hot with the use of carrageen. Presentation wise, it is possible to give food an uncanny gloss and work as a suspending agent.
Aside from these, the technique also serves to stabilize and thicken liquids. Such properties are excellent for sauces and creams. The viscosity provided by the gelling agents allow for more control with the use of fluids. Gelification with the use of certain substances may also be used for foaming, creating lighter dishes.
As mentioned earlier, the basic process of gelification occurs with the binding of macromolecules through a large amount of water. A common step taken with the use of this technique is the dissolution of the gelling agent. More often than not, the substances used to create gels will need to be dispersed in water to allow for hydration. With the presence of liquid the hydrocolloids absorb the water and become enlarged.
The macromolecules then become individualized as they move away from each other. Polymer chains slowly unfold with the attachment of water molecules. As a result of the unfolding hydrophobic and hydrophilic polymer chains are discovered. An association between this is created and the overlapping area is generated. As a result of these intersections, the water becomes "frozen" causing a gel to form.
Binding forces among the macromolecules will determine the characteristics of gelification. Stronger bound molecules will often result in higher rigidity as well as reversibility. Characteristics of the various properties can often be controlled through the amount of hydrocolloids dissolved in liquid.
In the case of reversible gels, bonds between macromolecules are broken through the use of a greater mechanical or thermal force than what is present in the bonds.
On a less technical note, the technique of gelification works similarly. Gelling agents are often presented in a solid form such as crystals, powder or sheets. These are then dissolved in either hot or cold water depending on the agent being used.
Commonly, gelling agents dissolved in cold water may be left to swell up before being liquefied with heat. Various gelling substances melt and solidify at different temperatures.
The liquefied gelling agents can then be mixed with different ingredients before being allowed to solidify. The set gels can further be manipulated by cutting or shaping. Others are set into molds before cooling. In some cases liquids other than water may be used in gelification, further enhancing the flavor of a dish.
Gelling agents come from various sources. The use of other natural thickeners aside from animal based ones emerged in the nineties. Common ingredients used in gelification methods include:
Agar Agar - Also known as just agar this thickening agent is obtained from the cell walls of the red algae. Agar-agar is cooked in boiling liquid and has a gelling capacity upon cooling. A unique characteristic possessed by this is its ability to retain firmness even after exposure to heat.
Carrageenan -Similar to agar, this gelling agent is extracted from certain red algae species. As a natural polymer fiber it produces gels which are flexible. In terms of texture, gels made from Carrageenan display a brittle but firm consistency.
Gellan Gum - A product of algae fermentation this gelling agent displays unique characteristics. This non-thermoreversible substance is water soluble. At high exposure to high heat it is elastic and freezes. Once set, it can withstand exposure to heat. At lower temperatures it sets as a strong gel which can withstand higher temperatures.
Gelatin - Derived from the process of collagen hydrolysis, this food protein comes from a number of resources primarily made from animal collagens particularly fish, pork and beef. Gelatin is heat sensitive and thermoreversable. Its ability to hinder water mobility affects texture and makes it versatile.
Methylcellulose - A chemical compound taken from vegetable cellulose, known also as modified vegetable gum. This gelling agent work differently from other similar substances since it sets when heat is applied giving way to a firm and rigid gel. In a cool state it can be used as a thickening agent.Pectin - Taken from the walls of plants that grow on land this is extracted mainly from citrus fruits. Commonly used as a gelling sugar, this is a usual ingredient in jams, spreads and sweet juices.