With the rise of molecular gastronomy the term hydrocolloid has become, shall we say, hot. Reader Hal has the good sense to ask: what the heck is a hydrocolloid? Well Hal, a “colloid” is a science-y sounding term that simply means: one substance dispersed in another. They’re all around us, colloids. There are solid-in-liquid colloids like house paint. There are gas-in-liquid colloids (whipped cream), gas-in-solid colloids (styrofoam), liquid-in-liquid colloids (salad dressing), liquid-in-gas colloids (bug spray), the list goes on. A kitchen hydrocolloid, as the name implies, is a colloid that involves water or some other mostly-water liquid like juice or broth. More specifically it’s a colloid in which water is the medium (the “continuous phase” it’s called in science-talk) and something else is being dispersed in it (the “dispersed phase”). The thing that is being dispersed in the watery medium is usually something like a starch or a gum or a protein. The goal being: to thicken.
Does that mean that the things most of us commonly use to thicken — flour, gelatin, cornstarch, pectin, fat, air — are “hydrocolloids” in this parlance? Yes. However traditional hydrocolloid-creating substances aren’t what most people mean when they use the word these days. Rather they’re referring to a new breed of thickeners/gelling agents that delivers non-traditional, even highly unusual, results. Like what? Maybe a sauce for a meat dish that has neither a cloudy look or a starchy mouthfeel (like a traditional flour-thickened sauce usually has). Maybe a custard that doesn’t have any egg flavor it. Or maybe a plate of clear “gelatin” noodles that don’t melt when they get hot.
So hydrocolloids are tools mostly for really ‘out there’ cooks? you might then ask. In a word: yes. However they have all sorts of industrial uses as well. I’ve been noticing them a lot in vegetarian meat substitutes, for example. Some of them are plant derivatives like aloe vera, agar-agar, carrageenan, mastic, locust bean gum and guar gum. Others are fermented thickeners like xanthan gum and gellan gum. Still others are sugar derivatives. Methyl cellulose, for example. Some thicken when they’re hot, others when they’re cold, some work alone, some need things like calcium or potassium ions to work.
A lot of these newer hydrocolloids are of limited use (at least to me). However if there’s a specific hydrocolloid you’re interested in, let me know and I’ll put up something about. Hydrocolloids have been hot stuff in the ingredients industry for a while now, and I’ve had experience with quite a few. If I have an answer to your question I’ll post it! Thanks Hal!