Is it just me or does that sound like the name of a town in Ireland? Oh right, it actually is the name of a town in Ireland, a little spot on the northeastern coast where this red seaweed-derived thickener was originally harvested and put to use. It’s been used to thicken puddings and custards in that region since at least 1810. Oh, and in Scotland as well. Locals would boil the local weed to extract the long-chain sugars, add borax to the hot solution to make them clump, then strain the whole mess out and dry it to a powder. The process was steadily improved to the point that in 1930 carrageenan became a mass-market product. It’s been a staple thickener for food makers (and some home cooks) ever since.
Yes, yes, I know some people hate carrageenan so this post is going to irritate them. I’ll say right now that I don’t buy the arguments that it’s poison and I’ll warn potential complainers not to bother sending me emails with links to small-scale independent studies that purport to prove it. They shall bounce off me like so many guided missiles off the meters-thick shell of Esgargantua, the ferocious mutant snail.
Carrageenan comes in three types: iota, kappa and lambda. Each one performs differently as they’re all derived from different seaweeds. I can say that all of them work at about the same concentrations as other hydrocolloids, thicken at both high and low temperatures and form gels that are clear and shiny. Kappa carrageenan forms nice firm gels, but requires potassium ions to work (it is a great gelling agent for milk-based mixtures). Iota forms softer, more elastic gels and needs calcium ions. Lambda is good only for thickening purposes but will act all by itself (it is also especially good for dairy applications). Sometimes they’re used in combination to create different effects. The down side of carrageenans? They don’t play well with acids.
Also, sorry about the picture, I sneezed.