Agar, or agar agar, is an extract from red algae that is often used to stabilize emulsions or foams and to thicken or gel liquids. While many people in America have only heard of it lately, it has been used for hundreds of years in Asian cooking. Agar is also relatively straightforward to work with and easy to find online, making it a great place to start experimenting with modernist cooking.
Agar is an amazing culinary ingredient. It's a thickening agent for soups, fruits preserves, ice cream, sauces, jelly-based desserts, custards, puddings and other tasty treats. Agar easily gels most liquids and the gels can range from soft to hard, depending on the amount used. It is also great at making dense foams, especially when used in conjunction with the whipping siphon. If an agar gel is blended, it creates a thick fluid gel that is perfect for sauces.
Agar is suitable for vegans, vegetarians and is suitable for most religious diets. It is also used as a clarifying agent in brewing.
One common non-culinary use of agar is for scientific purposes in the labs to provide a growth medium for organisms in a petri dish. In small quantities, this natural ingredient is incorporated into modeling clay for young children to play with. It is also used as an impression material in dentistry. Due to agar's high fiber content it can also be found in laxatives and appetite suppressants.
You can buy agar several places. We highly recommend ModernistPantry.com, they have great service and are really good to work with (because of this, we do have an affiliate relationship with them). In addition to online, It can generally be found in Asian supermarkets and health food stores as flakes or powder.
Natural agar is an extract from red algae and is white and semi-translucent with no discernible flavor. It produces a firm clear jelly and is rich in iodine and trace minerals.
The unusual and complex carbohydrates that form agar are a component of the cell walls of several species of red algae that are usually harvested in the Red Sea, eastern Asia and California, to name a few. Agar consists of approximately 80% fiber.
Agar is also known as Agar Agar, Agazoon Agar, Kanten (its Japanese name), China grass (in Indian cuisine). Agar is available in different forms: bars, flaked and powdered, and in the UK you are most likely to find it in the flaked or powdered forms.
The gelling ability of agar is affected by the acidity or alkalinity of the ingredients it is mixed with. More acidic foods, such as citrus fruits, kiwi and strawberries, may require higher amounts of agar. Some ingredients will not set with agar at all unless the enzymes in those fruits are first broken down by cooking. These would include fresh pineapple, figs, paw paws, papaya, mango and peaches. In addition, chocolate and spinach just seem to prevent agar from setting.
In order for agar to be used effectively it has to be correctly dispersed and hydrated.
In order for agar to work successfully it first needs to hydrate, or absorb water. To properly hydrate agar it must be brought to a boil at 212°F (100°C) and simmered for 3 to 5 minutes.
Agar does not hydrate well in acidic liquids, making gelling difficult. To get around this issue, first hydrate the agar in a neutral liquid and then add it to the acidic liquid.
Sometimes you do not want to bring the liquid you are gelling to a boil. In this situation you have two options to hydrate the agar. First, you can disperse and hydrate the agar in a small amount of the liquid and blend the rest of the liquid into it after hydration. Second, you can disperse and hydrate the agar in water, then blend the liquid into that.
With either method the temperature will drop quickly and the gel will start to set as soon as it gets below 113°F (45°C). Therefore it is advisable to warm up the liquid as much as you can in order to get the best dispersion once the agar has hydrated.
The amount of agar used will depend on the technique you are using it for.
The firmness of an agar gel is determined by the amount of agar used to create the gel. The more agar that is used, the firmer the gel will be. Typically 0.2% agar is used for soft gels increasing up to 3.0% for firmer gels.
Fluid gels are usually made out of gels with a 0.5% to 2.0% ratio; the more agar used in the original gel results in a thicker fluid gel.
Agar foams use 0.3% to 1.0% for light foams and 1.0% to 2.0% for denser foams.
Check out how to measure modernist ingredients for more information on ratios.
Creating a gel with agar results in a brittle gel. However, the firmness of the gel will depend on how much agar is used. Agar gels will usually range from 0.2% agar in a very soft gel to 3.0% agar in very firm gels.
To make a chewier, more elastic gel you can replace from 5% to 15% of the agar with locust bean gum. If you are using gelatin, it should be incorporated when the agar is added and at about the same weight as the agar.
Making an agar gel takes just a few steps. First disperse the agar in the flavored liquid you want to gel using a whisk or blender. Then bring the liquid to a boil for 3 to 5 minutes. Pour the liquid into molds and let it set at room temperature. The gel will actually set at 104°F to 113°F (40°C to 45°C) and remain a gel as long as it stays below 175°F (80°C).
Once it has set, the gel can be turned out, shaped, and plated. The gel will also last for a day or two, though it starts to lose some of its texture and moisture as it dries out over time through syneresis, the leaking of liquid from a gel. You can usually rehydrate the gels by placing them in water.
A nice property of agar gels is that they can be used hot or cold. They will not melt until they go above 176°F (80°C) which allows you to use them in soups or other hot foods. Please be careful serving gels that are at such a high temperature since they can cause severe burns because many people expect them to be cool.
They can also be melted and re-set multiple times without a loss in strength. However, you cannot freeze agar gels, since freezing causes a loss in liquid and texture, unless you are trying to clarify liquids through the freeze thaw technique.
Using agar is a great way to create a wide variety of gels. The amount of agar used ranges from 0.2% for soft gels increasing up to 3.0% for firmer gels. The addition of locust bean gum increases the elasticity of agar gels, making them hold together much better. For a good starting spot when making cubes, I usually use a 0.9% agar and 0.1% locust bean ratio.
Gel cubes can be made out of most liquids though I find cocktails, broths, or juices tend to work best.
One of the more interesting properties of agar gels is that once they are set, they can be reheated without melting. You can use this to make hot gel cubes of any of the infused broths, or any hot cocktails.
You can either set the gel in silicon molds, or just use a rectangular container and then cut it into cubes once it has set. When the gel is setting, you can also add garnishes to it, creating whimsical taste sensations.
If you are making alcoholic gels, I recommend first combining the agar with any juices or mixers then boiling it before whisking the alcohol in at the end. This helps prevent any evaporation of the alcohol. The cubes can be made ahead of time but be sure to refrigerate them if you aren't serving them for a few hours.
Combine all the ingredients in a pot and blend well to combine. Bring to a boil while stirring occasionally. Let simmer for 3 to 5 minutes, stirring regularly.
Pour the agar mixture into a mold or a rectangular container and let it completely set. Once set, cube the gel.
Fluid gels are substances that behave like a gel when at rest and like a liquid when force is applied. Ketchup is probably the best know example of a fluid gel, as anyone that has struggled to get it out of the bottle, only to have it flood their hamburger, can attest. Other common examples are puddings and custards.
Once you understand how agar gels work, it is very easy to create fluid agar gels. The simplest way to create an agar fluid gel is to create a normal agar gel then puree it until smooth using an immersion blender or standing blender. It is ready to use as is or you can thicken the fluid gel by adding some xanthan gum or thin it out by adding water or another liquid.
To create the gels used for fluid gels a ratio of 0.5% to 2.0% will result in a fluid gel ranging from runny to pudding-like.
Most gel noodles are made with agar. It is mixed into a liquid and hydrated, then pushed into tubing to cool. Once it's cool, it is removed from the tubing and can be used as noodles or garnish. A 1% ratio of agar usually works very well but for a stronger noodle I will use 0.9% agar and 0.1% locust bean gum.
Agar foams are made from agar fluid gels that are dispensed from a whipping siphon. These foams are thick, fine foams that are very dense. Because agar holds its shape under higher temperatures these foams can be served hot or cold.
For agar foams, the more agar you use the denser the resulting foam will be. For light foams, a ratio of 0.3% to 1% works well. For denser foams 1% to 2% is recommended. You can also add gelatin, locust bean gum, or xanthan gum to change the density of the foam.
Gel pearls are made by adding agar to a liquid and hydrating it. The liquid is then dripped into a glass of very cold oil. As the liquid sinks it forms into a sphere which then gels.
You can get creative when applying the coating in order to fashion different end results. For example, dipping the food directly into the gel coating gives a more solid appearance where brushing it on can give a varied look. After the first coating hardens you can quickly reapply it if you want a thicker coating.
Gel sheets are thin layers, similar in thickness to a flour tortilla but made entirely of a gelled liquid. There are many ingredient combinations you can use for gel sheets but I usually use a 0.9% agar and 0.1% locust bean gum mixture or a 1.2% agar and 1.4% gelatin combination. Both of these result in good gel sheets.
The gel sheets are made by adding the gelling ingredients to a liquid and hydrating them, then pouring the liquid onto parchment paper or a silicon mat in a very thin layer. Once the gel fully sets the sheet can be used.
The end result is a flexible sheet you can drape over or wrap around foods. Gel sheets can be used as a garnish or topper for dishes or cut into rounds and used like ravioli.