Vacuum-set foams: Aerated chocolate

It’s funny sometimes, the things that give me the impetus to move projects off of my “to do” list and drive me into the kitchen. In this case, it was Halloween. After trick-or-treating was over, our basket of treats held a few leftover Aero bars, which I had always thought my husband disliked. When I saw him take one, I asked him about it, and he observed that he liked the texture, just not the quality of the chocolate.

Surely I could do better.

In typical modernist home-cook style, I’ve got at least four different recipes for aerated chocolate: one in The Fat Duck Cookbook, one in In Search of Total Perfection, one in Chocolates and Confections, and one in Modernist Cuisine. (Of course.) They all differ slightly, but the fundamentals are the same: temper chocolate (Callebaut milk chocolate, in my case), add some pure fat (oil or cocoa butter) for additional fluidity, charge in a whipped cream siphon, and dispense. This creates a chocolate foam that sets, trapping all the bubbles in a network of crystallized cocoa butter. (Ideas in Food also offers an aerated chocolate dessert, but it’s based on a different principle, being more of an aerated ganache gel than a pure aerated chocolate. I’m looking forward to trying it, too.)

An optional step in these recipes is to make what Modernist Cuisine calls a “vacuum-set foam” by placing the freshly foamed chocolate in a vacuum container, pulling a vacuum on it, and leaving it under vacuum until it has set. This causes the bubbles to expand, creating a much lighter texture in the finished chocolate. I’ve tried this technique before with the aerated mango sorbet recipe in Modernist Cuisine, which is “set” through freezing, but the vacuum pump on my FoodSaver isn’t strong enough for that recipe.

Fortunately, it is strong enough to work with chocolate, and the results were impressive. As you can see in the photo above, the vacuum-set chocolate has much bigger bubbles than the one set at ambient pressure. The only mistake I made was that I forgot to line the ramekins I used to mold the chocolate, which made it hard to get the finished product out in one piece! It would be cool to be able to enrobe this kind of aerated chocolate, or use it in a layer cake like the recipe in In Search of Total Perfection, but for that, I think I would need a square vacuum container

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9 Responses to “Vacuum-set foams: Aerated chocolate”

  1. Fun stuff eh? I consider the vacuum essential, not optional but that’s probably just being picky. The texture is just much nicer. For a cake layer, I once lined the bottom of a cake pan with caramelized rice crispies and unflavored pop rocks then sprayed aerated white chocolate cut with a blend of grapeseed and toasted walnut oils, put it under vacuum and let it set. It was pretty tasty. I’ve been toying with the idea of using peanut butter instead of oil or cocoa butter and seeing what happens but haven’t got around to it yet.

  2. I agree that the texture of the vacuum-set chocolate is definitely much better. On the other hand, the Greweling recipe calls for three charges of nitrous, and I only used two, since I knew I would vacuuming most of the batch anyway, so that might be part of the difference. I don’t make a lot of cakes, but this has me thinking about what I could make, for sure. Do you think peanut butter would give it enough fluidity? Maybe if you could find an unrefined peanut oil you could get that chocolate-and-peanut-butter flavour.

  3. I’m guessing the peanut butter probably wouldn’t work as is. I think it would require combining it with an oil (peanut being the obvious choice) to thin it quite a bit. I considered using roasted peanut oil but it would be a much more expensive way to go for doing large amounts. Have you found the tempering step beneficial? I haven’t found a need to temper the chocolate pre-aerate for anything I use it for. I’m sure there’s a reason it’s sometimes suggested but I haven’t seen any real benefits to the end result. Of course I’m usually using it as a dessert component of some type, not enrobing or molding, so maybe that’s the difference?

  4. I’ve only done it this one time, so I can’t say for sure whether the tempering is beneficial. I think every recipe I looked at said to temper it. I assumed it would just offer the same benefits as tempering always does; the only time I don’t temper is if I’m making ganache. (And even then, I’ve heard that it’s better to temper.)

  5. Hi. You refer to a number of recipes, but all of them are printed on books. Are there any online recipe to follow, in order to try the aerated chocolate by ourselves?
    Can you share the recipe that you tried?
    BTW, I own the fat duck book and I saw the tv episode of In search of Perfection [forest gateau] in which Heston make his chocolate, but nonetheless I wonder if you followed other ratios, or techniques.

  6. Hi Isaia, I sort of combined several of the recipes I found, but essentially it was this: temper a bunch of milk chocolate (Callebaut 665 NV for me), measure out 250g into a bowl, add 33g of peanut oil, stir to combine. Transfer to a warmed half-litre cream whipper; I warmed it with a heat gun. Seal, charge with two nitrous oxide cartridges, shaking well after each one. Immediately dispense into desired molds and vacuum to expand.

    Hope that helps!

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