Regarding Hydrocolloids

With the rise of molecular gastronomy the term hydrocolloid has become, shall we say, hot. But what exactly is a hydrocolloid? “Colloid” is a science-y sounding term that simply means one thing dispersed in another. They’re all around us, colloids. There are solid-in-liquid colloids like, say, paint. There are gas-in-liquid colloids (whipped cream), gas-in-solid colloids (styrofoam), liquid-in-liquid colloids (salad dressing), liquid-in-gas colloids (hair spray), the list goes on. A kitchen hydrocolloid, as the name implies, is a colloid that’s based on water or some other mostly-water liquid like juice or broth. Which is to say it’s a colloid where water is the medium that something else is being dispersed in — the “continuous phase” as it’s technically called — and the something else that’s being dispersed (the “dispersed phase”) is a gum or starch or a protein.

All the thickeners we commonly use in the kitchen and that I’ve listed so far — wheat flour, air, fat, pectin, gelatin, cornstarch etc. — are (or can be) hydrocolloids. However that’s not what most people mean when they talk about hydrocolloids these days. Rather they’re referring to a new breed of thickeners/gelling agents which, either by themselves or in combination with others deliver at the very least non-traditional, and at the most highly unusual, results. Like what? Maybe a sauce for a meat dish that has neither the cloudiness nor the starchy mouthfeel of a roux-thickened sauce. Perhaps a custard that has no egg flavor it. Or possibly a plate of clear gel noodles that can be served piping hot.

Modern kitchen hydrocolloids, in essence, are thickeners that give cooks options they never had before. They are highly variable things, ranging from plant derivatives like aloe vera, agar-agar, carrageenan, mastic, locust bean gum and guar gum to fermented thickeners like xanthan gum and gellan gum to sugar derivatives like methyl cellulose. Some thicken when they’re hot, others when they’re cold, some work alone, some need calcium or potassium ions to work. As with thickeners generally, it’s hard to know where to start with hydrocolloids. Frankly a lot of them 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 are hot stuff in the ingredients industry and I’ve had experience with quite a few. If I have an answer to your question I’ll post it!

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9 Responses to Regarding Hydrocolloids

  1. Jim Hu says:

    off topic, but I thought of you when I read this at Serious Eats

    At present, I uncovered just four Chicago cafés producing on a regular basis, but each has noticed a recent increase in demand.

    I’m picturing readers of your canelés posts prowling the streets of Chicago…

    • joepastry says:

      That’s fabulous Jim. Thanks! I still shake my head sometimes at my old home town: the City of Big Shoulders, Tool Maker, Stacker of Wheat…eating things like canelés now. But times change and good food is good food…what are you gonna do? Save your pennies and go to Alinea I guess!

      But I’d be flattered indeed if the blog had anything to do with it. Oh, the time I put in on those little buggers. I still have flashbacks! Hehe…thanks!

      - Joe

  2. naomi says:

    You are a smart one. I went to a bakery open house this weekend to see the kitchen. I mentioned my hesitancy in bread making but said I read a lot. She said that was good, and there were some good sites on the net. Of course, I replied, “JoePastry,” and she got a big grin and said, “Oh, yes, he’s good.” You’re everywhere.

    • joepastry says:

      Ha! That was a little boost that felt good this morning I must confess! Thanks very much, Naomi!

      - Joe

  3. Philip Scott Thomas says:

    Joe –

    A few years Heston Blumenthal had a series on the telly called How To Cook Like Heston. In one episode he made a chicken and ham pie. He wanted a heat-resistant sauce for the filling, so he used agar-agar.

    The result set up like a beaker full of stiff jelly. But after he wazzed it with his stick blender it turned into a thick sauce, something akin to the more traditional roux-based filling, but which didn’t break down in the heat of the oven.

    It’s a technique that’s interested me since, though I’m yet to try it myself. Where on earth does the home cook find agar-agar?

    FWIW, his recipe is here.

    • joepastry says:

      Hey Philip!

      Nice to hear from you. Yes agar-thickened gels are extremely heat tolerant (low “thermo-reversibility” I think is the term). It’s fun stuff to play with. You can find agar in quite a few health food stores. I suggest looking there first. Thanks for the link!

      - Joe

  4. Frankly says:

    I have a friend who is strictly vegetarian. I like to make some desserts with gelatin and of course that is right out (cow hooves and all). I have not looked at replacing “the knox” with agar-agar but have thought I probably should. Do you have any advice/tips/great ideas?

    On all those other things: the wife & I have had a couple of meals at those places where you get those foods and its fun, some of them are actually very tasty and all. But if you ever start messing around with “foam of green pea and beet aioli on a bed of freeze dried tamarind” I will abandon you! Thats not cooking thats an ADHD kid that got a Gilbert chemistry set for Christmas and got bored making rotten egg smell! -and I would know :)

    • joepastry says:

      Ha! I’ll remember that, Frankly. Agar-agar is a a good substitute for gelatin. I’ll explain why in a post, hopefully today if I can find some of the stuff! ;)

      - Joe

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