Theory of Gel.
Time and again I have seen that there is a lot of confusion when it comes to gelling and thickening agents. So I thought it is time to write another article in my attempt to make it as clear for you all as possible.
What are gelling / thickening agents?
These are ingredients used to thicken a sweet / savoury product. According to the use and functionality of the dish, different agents or a combination is used. Cold desserts, hot desserts, soups, sauces, sweets, ice creams everything will have a different agent being used according to the desired result.
Thickeners close to it’s original form without any extraction.
1) EGG YOLKS
When mixed with dairy or non dairy liquids and gently heated, acts like starch in thickening the sauce/ custard which gives a silky smooth texture with a melt in the mouth feeling. It is not susceptible to high heat and needs to be tempered before using. ‘Tempering’ is a process of gently bringing the temperature of the egg yolks up by whisking hot liquid into it.
2) FRUIT PEEL
Certain fruit skins like citrus, guava, cherry etc. have ‘natural pectin’ in them which helps in self thickening while making a pie filling or fruit sauce.
3) LEGUMES AND PULSES
Almost all legumes and pulses have starching and gelling properties in their skin. The degree of it, might vary. The most popular being chickpeas which lays the foundation of a great vegan substitute for egg – Aquafaba. This is obtained by cooking the chickpeas slowly for a long time until the skin gives out the “thickener” which can then be sieved and used separately.
A famous example is “Dal Makhni” which is traditionally thickened by the slow cooking of the dal which helps it’s skin thicken the mixture.
4) CREAM / CHEESE
Both these dairy products have fats which help thicken a dish, be it sweet or savory. In order to maintain thickness with cream or cheese in a dish, it should not be heating at a very high temperature.
DERIVED / EXTRACTED GELLING AGENTS –
1) FRUIT PECTIN
This is extracted from the skin of citrus and other fruits. It activates at room temperature when mixed with a liquid. Upon heating, it gives out its gelling properties. It is a strong gelling agent depending upon its source, therefore it stays put even when it is frozen and doesn’t split. It is used to make fruit jams, vegetable and fruit jellies.
2) AGAR AGAR
This is a seaweed with strong gelling properties. Since it is a sea plant, it is 100% vegetarian. it activates only upon vigorous heating.
There are 2-3 forms of agar agar –
(a) Strips – This needs to be soaked in hot water to soften for a few minutes and then added to a liquid which then boils to form a gel. This will never work without getting soaked in hot water first. This is also known as ‘CHINA GRASS’
(b) Flakes – Same as above.
(c) Powder – Unlike the strips or flakes, this does not need any soaking. It needs to be thoroughly mixed with water or any other neutral liquid at room temperature first, and then added to a liquid which will then be boiled to activate the gelling properties of agar. If mixed directly with a hot liquid, it will clump up and will never break down.
This is also a seaweed discovered in Ireland and now popular all over. This needs to be soaked in warm water to activate and then boiled into the liquid which needs to be set.
It is a soft setting agent as compared to its vegetarian partner – agar agar, therefore, whenever you’re looking for a softer set, you should use this instead of agar. It works better with liquids having some fat content like dairy products than fruit juices etc. They can be extensively found in things like ice creams, sour cream and yogurt.
This is extracted from the bones and skin of cattle, animals and certain fishes. Due to its source this is 100% non vegetarian.
This is added to a liquid at room temp or cold depending upon the source. Once it swells up, it is then added to a hot liquid or melted gently then added to a liquid which needs to be set.
Gelatin splits when overheated. It has a very low melting point and that is why it melts in the mouth from our body temperature, which is why it is the most popular gelling/setting agent among pastry chefs around the world.
It comes in two popular forms with different varying grades (bronze, silver, gold and platinum) in ascending order of strength.
(a) Sheets – This is soaked in cold water first to soften and then directly added to the hot liquid which needs to be set.
(b) Powder – This needs to be mixed with room temp liquid in order to activate. Then melted gently before adding to the liquid which needs to be set.
The term ‘gelatin’ is very widely known for being something that is used to make jellies and set things. This is why companies sell agar agar / pectin / carrageenan as ‘VEG GELATIN’.
Please don’t get confused and do read the contents of the packaging.
**THERE IS NO SUCH THING AS VEG GETLATIN. It is just a marketing term that companies use in order to relate to the public**
It is similar to the marketing terms like “Vegan Egg”, “Vegan sausage” (sausage made of soy or tofu), “Eggless Omlette”, “Vegan Milk” (used for oat/almond/cashew extracted liquid), “Dark confection” (used for mock chocolate).
DERIVED / EXTRACTED THICKENERS –
All kind of starches are derived from their source which intern can be used as thickeners.
1) ALL PURPOSE FLOUR
This is extensively used in savoury cooking (especially french and Italian) for thickening sauces. This is first added to a fat, cooked off, then introduced to a liquid that needs to be thickened. This is done primarily to ward off the taste of the flour. If used as the only starching ingredient in a dish, it shouldn’t be used to freeze, as the starch splits and gives out water.
2) CORN FLOUR / CORN STARCH
This is the most commonly used thickening starch for sweet and savoury. This is essentially a hot starch. It activates when heated. It doesn’t work with extremely sweet or citrus or high fat liquids. If overheated or over frozen, the starch molecules will break down and the liquid might separate. Corn starch needs a sufficient amount of liquid to thicken, otherwise it will not work.
3) TAPIOCA STARCH
This is extracted from the root of cassava plant. This has high starching abilities. It is stronger than corn starch, therefore it doesn’t split when frozen. It has a much better mouth feel than corn starch.
4) POTATO STARCH
This is the pure starch from potatoes. This activates when mixed with a warm liquid. It deactivates when heated. Therefore, it is a very good finishing starch. If you have fruit sauce/ caramel/ soup etc that need to be thickened without heating it all over again, using potato starch would be the best option.
There are several other kinds of GUMS and chemical thickeners / gelling agents as well –
1) ALGINATES –
These are salts of Alginic acid, a viscous gum formed by the cell walls of brown algae. Food uses include thickening fruit drinks, soups and sauces, and as a gelling agent in jellies and bakery fillings. (Source – Faia.uk)
2) GUM ARABIC
This is made from the sap of the acacia tree and is a mixture of saccharides and glycoproteins (proteins with attached sugar molecules). This is used to make hard jelly sweets in Africa and Middle East.
3) GUAR GUM
This is extracted from guar beans, which predominantly grow in India. It is a type of water-soluble gum which combines well with high sugar content in a liquid. Therefore this is used to increase the elasticity of things like fondant, sugar paste. This is also used as a stabilizer in ice creams and commercial yogurt.
4) XANTHAN GUM
This is made by the fermentation of glucose or sucrose with the microorganism Xanthomonas campestris. It acts as a stabilizer and helps prevent the emulsion from separating. This is also popular in cold desserts and Ice creams since it helps prevent the formation of ice crystals.
5) SODIUM CARBOXYMETHYL CELLULOSE better known as CMC
This is a water-soluble semi-synthetic thickener, made by reacting cellulose with an acetic acid derivative. It is used as a stabilizer in ice creams and frozen desserts to prevent the formation of ice crystals.
These are the most common and popular gelling and setting agents. There are many others which are used in molecular and experimental kitchens which are probably not as popular. Every chef has his/her own concoction or proportion of these agents to be used for the best mouth feel.
If you’re up for it, you should form your own!!
All the best!