Carrageenans are linear sulfated polysacharrides extracted from certain species of red algae (seaweed) of the Rodophyceae class. To extract carrageenan from the raw seaweed, the seaweed is harvested, dried, and processed.
There are many types of Carrageenan beyond kappa, iota, and lambda, but we only use these three types in cooking: κ-Carrageenan (kappa), ι-Carrageenan (iota), λ-Carrageenan (lambda).
Carrageenan has the ability to complex or interact with proteins and is used extensively to thicken, gel or stabilize dairy based solutions. Carrageenan is not a surfactant, but it will stabilize existing emulsions. The 3-dimensional network which helps stabilize emulsions also functions to suspend particles.
Kappa Carrageenan gels as it reacts with calcium or potassium salts. In the presence of calcium, Kappa Carrageenan forms stiff and brittle gels. But in the presence of potassium salts, Kappa Carrageenan forms very firm and elastic gels.
Lambda Carrageenan will not form a gel, but can be used as a thickener.
Iota Carrageenan is a great thickening and gelling agent mostly used with fruits and dairy to form a heat-reversible and flexible soft gel. Iota Carrageenan requires calcium ions to develop a gel and as all carrageenans, it is vegetarian and a great alternative to gelatin. Iota Carrageenan forms a soft gel, especially in the presence of calcium.
How to Use Carrageenan
Concentration Range: Iota Carrageenan thickens at 0.02%-1% concentrations and gels from 1%-1.5%. Kappa Carrageenan thickens from 0.02%-1.5% and gels above 1.5% concentration. To make an eggless custard or flan, use 0.2% Iota with 0.15% Kappa. For a cold terrine, use 0.25% of Iota with 0.25% of Kappa. If you want a firm and brittle jelly, combine 0.2% Kappa with 0.4% Locust Bean Gum. To coat food with a firm gel, combine 0.45% of Iota with 0.35% of Kappa. To thicken a cold dairy sauce, use 0.1% of Iota. To make a thicker cold fluid with the consistency of pudding, use 0.2% of Kappa with 0.35% Iota. Keep in mind that these concentrations are just for reference and results will vary depending the calcium or potassium (for Kappa) content.
Dispersion: Both Iota and Kappa Carrageenan can be dispersed in cold water with the help of a blender. To facilitate dispersion you can premix the carrageenan with other dry powder ingredients in the recipe or 3 parts of sugar by weight.
Hydration: Iota and Kappa Carrageenan need to be heated to over 79 °C (175 °F) to hydrate and they gel as they cool.
Lambda Carrageenan dissolves readily in cold liquids. To use Lambda Carrageenan, simply add the powder to the desired liquid and stir or blend to thicken.
Setting: Once dispersed, the carrageenan solution needs to be heated to about 79°C / 175°F to be completely hydrated and as it cools down below 45°C /113°F, it starts to gel. Increasing the amount of calcium or potassium available will make the gel stronger and allow gels at higher setting temperatures and lower concentrations.
Stirring a Iota Carrageenan preparation will prevent the forming of a gel, but if let to rest, the broken gel will form again.
If you’ve been following along, you’ll notice that Carrageenan resembles sodium alginate in that it gels in the presence of specific ions (calcium and potassium). That means it’s indeed possible to use both Iota and Kappa Carrageenan for reverse spherification. Use these ingredients at a concentration of 1.5% and a corresponding bath containing either calcium lactate or potassium phosphate at 5% concentration.