The important things to remember when making gels are similar to the considerations you should keep in mind when using any thickener. Before using a hydrocolloid take a quick look at our hydrocolloid guide.
How to select the right hydrocolloids for your gel
To select the right hydrocolloid there are a few things to consider.
- Is it going to be served hot or cold? Is the base of the gel clear or cloudy? Is the base acidic? Creamy? Has ions such as calcium?
- What gel properties are you looking for? Brittle? Soft? Chewy? Or do you want to make a fluid gel?
- How are you going to present it? Are you going to cast the gel? Are you going to use it to cover another solid ingredient? Are you going to cut it with a knife?
Once you know the answer to these questions, select the right gelling agent from our hydrocolloid guide. For cold elastic gels you can use gelatin, kappa and iota carrageenan (especially if dairy) for example. For cold brittle gels you can use agar or gellan. For hot elastic gels you can use gellan with xanthan gum, for firmer gels use agar with locust bean gum. For hot brittle gels you can use agar and gellan. For cold fluid gels you can use gelatin, iota and kappa carragenan. For hot fluid gels you can use agar, gellan, agar with xanthan gum. For spherification, take a look at the Spherification Class.
Dispersion and Hydration
When working with a hydrocolloid the first step is dispersion. For example, cornstarch disperses in cold water, but not hot. Flour disperses in oil, but not water. In these situations, all you need is a whisk or hand mixer to properly disperse your hydrocolloid.
After dispersion, the next step is hydration. Hydration is what happens when water interacts with the tightly wound molecules of a hydrocolloid and causes them to open up.
Unlike many thickeners, most gelling agents benefit from heating to a simmer or low boil. While you could use a blender to help hydrate the hydrocolloid, blending it could introduce air, which would make your final product opaque.
A notable exception is egg white powder, which should be hydrated in warm water and not hot. If heated, egg white powder coagulates into a thermoirreversible gel, just like normal egg whites.
Our hydrocolloid guide will explain you how to disperse and hydrate each hydrocolloid.
Once the hydrocolloid has been dispersed and hydrated properly, the most common reason of a recipe failure is the interaction with other ingredients in the recipe. So pay careful attention to the Interactions and Tolerance section of each ingredient in the hydrocolloid guide. Acidity, sugar, alcohol, salt, calcium content and other ingredients can interfere with hydration and can weaken the gel.
Gel Setting Time and Texture
Finally, even after a hydrocolloid has been successfully dispersed and hydrated, keep in mind that its texture can continue to change over time. For cold-set gels like gelatin or agar, the gel will strengthen when held at gelling temperatures for several hours.