Gel-icious Foods!

We have all enjoyed a sweet jam on bread or jelly sprinkled with sugar, at least once in our life. If so, then we are no strangers to the gels in our food. Gels are found in a lot of our everyday food products. They are semi-solid substances and can retain large amounts of water within their structure. Gels are formed when gelling agents (mainly polysaccharides and proteins) are dispersed in water. Gels impart a wide range of textures from soft and creamy (like pudding) to firm and elastic (like gummy candies).

Gelling agents come from a variety of sources like plants, animals, seaweeds, and even saps (like gum tragacanth)! The famous Bombay halwa, known for its vibrant colours and soft chewy texture is among the oldest gelled product in Indian cuisine. It is made up of merely 6 ingredients, with cornstarch being the primary ingredient that creates the beloved chewy texture. Guar gum extracted from guar seeds, native to India is used in a variety of foods due to its gelling and thickening properties.

Agar (from red algae), alginates (from brown seaweeds like kelp), and carrageenan (from red seaweeds) are some of the most common gelling agents used in many food products. The use of seaweeds as gelling agent dates back to 1658, when agar’s gelling qualities were first identified in Japan through the extraction of the substance from a red seaweed using hot water.

Many proteins from animal sources act as gelling agents as well. The sweet delicacy “Kharwas” made of colostrum is often sold on the streets of India and is loved by many. This jiggly texture is created because the proteins in the colostrum rearrange themselves into a gel-like structure when heated. Gelatin is one of the best gelling agents in cooking and is used in many cuisines around the world. It is derived from collagen found in animal skin, bones, and connective tissues.

In terms of gel formation, it happens when molecules of the gelling agent come together to create a 3D network, trapping water between them. These networks are called ‘junction zones’. The process of gelation is essentially the formation of these junction zones. Gelation happens mainly in three ways. It can happen by linking the chains of hydrocolloids with ions. Polysaccharides like alginate and carrageenan are examples of such gelation.  Some gels are formed at cool temperatures where the powder is dissolved in warm water and then cooled to form a gel (agar and gelatin). While some require heat to form a gel, like those made from starch.

So how do you pick the right gelling agent for different products? The choice of gelling agent for a food product depends on its characteristics. The formation of gels in food can be influenced by various factors. The characteristics of gelling agents, such as gelatin, agar-agar, pectin, and starch, vary, which influences their capacity to produce gels. Gels formed at higher concentrations are harder, but those formed at lower concentrations may be weaker or not develop at all. Additionally, gels develop at particular temperatures. For example, gelatin gels form when they are cooled below room temperature, while pectin gels require higher temperatures. Some gels are also impacted by the pH. Gelling agents like alginate require specific ions (calcium ions) to form a gel.

Understanding these factors is crucial for getting the desired gel in food products. Let’s get to know some of the common gelling agents and their applications in food.

Alginate, a cold-water-soluble gelling agent, is preferred for re-structured foods, instant bakery custard, puddings, desserts, and bakery creams. They are incompatible with milk, except with calcium sequestrants.

Carrageenan is a hydrocolloid used in dairy desserts like puddings, milkshakes, and ice cream, due to its ability to form gels in milk at lower concentrations. It is also used in cake glazes because of its high gelling temperature, and in processed cheese because of its firm and quick setting behaviour.

Pectin is primarily used in jams and jellies due to its high methoxyl requirement for gelling. It is preferred for acidic fruit gels due to its acid stability. Low methoxyl pectins are used for reduced sugar jams and jellies, as well as in bakery glaze production.

Gelatin is a versatile gelling agent used in jellied confectionery, yoghurt products, low-fat spreads, and sugar confectionery due to its low-temperature melt-in-mouth and slow-setting properties. Marshmallow, an aerated gelled confectionery, uses gelatin for its elasticity and clarity, also used in table jellies for its clarity.

Agar is used in various food applications, including bakery products, confectionery, Japanese desserts (like Yokan, and Mitsumame), meat, fish, poultry products, ice cream, peanut butter, and beverages. Gels of carboxymethyl cellulose (CMC) and hydroxymethyl cellulose (HPMC) melt when heated and are often used in cake batters, whipped toppings, and salad dressings.

Gelling agents have other applications as well such as fat replacements in food products and encapsulation of bioactive compounds. People have become more interested in low-fat foods because of the rise in chronic diseases caused by the consumption of fats. However, reducing fat creates a negative impact on the texture and flavour of the food.  Pectin, carrageenan, and cellulose can act as good substitutes for fat. Researchers have even developed hybrid hydrogels with desirable properties to replace fat in mayonnaises.

Gels are also gaining attention due to their encapsulating properties, efficiency, and low price. They entrap the bioactive compounds inside the gel and ensure the effective release of these compounds. Gels of CMC, pectin, and alginate have shown excellent encapsulating characteristics.

Gels and gelling agents have proved their versatility for decades offering texture, stability, and flavour enhancement in many food products. So next time you enjoy a jiggly dessert remember the magic of gel behind it!

References-

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2. Saha et al. (2010). Hydrocolloids as thickening and gelling agents in food: a critical review (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3551143/) (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3551143/#CR51)

3. Liu Bin et al. (2022) A comprehensive review of food gels: formation mechanisms, functions, applications, and challenges (https://www.researchgate.net/publication/362648462_A_comprehensive_review_of_food_gels_formation_mechanisms_functions_applications_and_challenges)

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5. Vaclavik et al. (2007) Essentials of Food Science. Springer Science & Business Media

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