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What happens when you “bloom” cocoa powder?

So asks reader Konrad in Poland. And he’s not talking about what happens when you store bar chocolate improperly and you get that powdery film on it. He’s referring to the process of combining cocoa powder with boiling water. It’s a step that’s used in many cake and brownie recipes to boost chocolate flavor.

Konrad, thanks for a fun question. “Blooming” does a couple of things to cocoa powder. Firstly and most importantly, it frees up bits of cocoa solids to disperse in the batter. Cocoa powder appears uniform when you look at it, but it isn’t. If you were to examine it under a microscope you’d see that, like flour, it is composed of many different-sized bits of ground endosperm, a large number of which are at least partially sheathed in pieces of membrane, which is found in abundance throughout the endosperm itself. Those pieces of membrane don’t have much flavor. Which means that any bit of surface area they occupy on the endosperm particle is that much cocoa we don’t get to taste, because the membrane prevents the cocoa from contacting our taste buds. Boiling water helps those bits of seed coat and membrane to release, and as a result the chocolate flavor is enhanced. Some claim that combining cocoa with boiling water doubles the chocolate flavor. That seems overly optimistic to me, but it might well be true.

Another thing that boiling water does is extract flavor compounds from cocoa endosperm in the same way that hot water extracts flavor compounds from ground coffee seeds (they really aren’t beans, not to be pedantic). However it’s important to stress that there’s a lot less flavor, ounce-per-ounce, in ground chocolate that there is in ground coffee, so while hot water will pull out some volatile oils and other flavor-giving compounds, it won’t produce anything like what you get when you make a cup of pour-over coffee. That much was made clear during the short-lived “brewed chocolate” fad from several years ago. More than a few people were disappointed in the stuff, which tastes more like a medium-strong chocolate tea than it does a real cup off hot chocolate.

And just in case you were wondering, the answer is no, more boiling time won’t give you more chocolate flavor. Yes, technically if you keep boiling ccocoa you will extract more oils and such, however not all of the locked-in flavors in ground cocoa are things you want to taste in quantity. These include bitter alkaloids and puckering tannins, which are better left where they are. So any time you bloom cocoa it’s important that you simply expose the cocoa to boiling water, not simmer it.

So Konrad, I suppose the answer to the last part of the question is that “blooming” is desirable in any instance when you want to maximize chocolate flavor. Which I guess for most of us is most of the time. But it’s important not to overdo it. As stated above, there can be such a thing as too much chocolate flavor. That said, I generally always look for an opportunity to bloom cocoa powder in something cake-like: a layer, a brownie, a cookie. Though sometimes there isn’t enough liquid in the recipe to do that. Such is life.

So that’s what I know Konrad. Hope this helps. And thanks again!

6 thoughts on “What happens when you “bloom” cocoa powder?”

  1. Thank you very much for the answer. It is easier to apply something when you have some idea what’s going on.

    1. Interesting! I myself associate “pits” with drupes, but then I’m no botanist, that’s for sure.

      Many thanks Eric!

      – Joe

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