Speaking of those “gray streaks”…

Why exactly does “fat bloom” happen when melted chocolate re-solidifies? So asks reader Wendi. That’s a great question and it all has to do with cocoa butter crystals. Chocolate is full of them, at least when it’s in solid form. That’s partly a factor of cocoa butter’s composition, which is unusually uniform. It’s made up of just three different types of fats (as compared to butter which can have dozens). The reason that uniformity makes cocoa butter so crystal-prone is because similar molecules tend to stack up on one another like LEGOs under the right conditions, forming solid masses.

But here’s the rub: depending on the way in which melted cocoa butter is allowed to cool and harden, there are six different types of crystals that those three different fats can form. Only two are stable and uniform and the rest are comparatively unstable and random. Tricking the fat molecules into forming only (or at least mostly) the stable, uniform kind is what tempering is all about.

But I digress. Depending on how you’re going to use the chocolate, random crystallization can be a problem. For reasons that are probably obvious at this point, random crystals have a softer texture than uniform ones, so there’s less “snap” in un-tempered chocolate. Also it’s duller in appearance because all those random formations don’t bounce light rays back as efficiently. But worst of all are unsightly grey streaks which happen when molecules of cocoa butter get squeezed out of the main mass (another side-effect of random crystallization) and crystallize haphazardly on the surface. This is why, if you’re planning to use melted chocolate as a coating of some sort, it should be tempered, since you never know when those crystals will suddenly appear during cooling and ruin a lovely finish.

Unless you’re using an inexpensive coating chocolate. In which case you have nothing to worry about from a crystallization standpoint. And why is that? Because while cheap coating chocolate has cocoa solids in it, it has little if any cocoa butter. That’s what makes it cheap, because cocoa butter is the most expensive component of the cacao bean. No cocoa butter means no rampant crystallization and a consistent finish. You just melt the stuff, apply it and go on your merry way. As I argued in the post below, that’s great in many cases — like holiday cookies.

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6 Responses to Speaking of those “gray streaks”…

  1. Sue says:

    What’s the best homemade equivalent to that handy cheap chocolate coating, if I’m too lazy to go out and track down Wilton melts, Candiquick, or the like? :)

    • joepastry says:

      You don’t need to go to that extent, though those coatings are available in most cake decorating and candy making supply shops. In general the less expensive the chocolate, the less cocoa butter it will contain. Hershey’s, Nestle, Baker’s and even some of the no-name chocolate coating brands contain the cocoa butter substitutes that chocolate lovers complain about but which actually have a functional use (as described here).

      Thanks for the comment Sue!

      - Joe

  2. rainey says:

    But refrigeration prevents (retards? reduces?) the likelihood of bloom in untempered chocolate, no?

    I just finished making Alice Medrich’s untempered truffles. She chooses to coat them in untempered chocolate since she says it melts instantaneously in the mouth and, so, has a different flavor and experience. OTOH, sometimes when I’m not interested in shipping them frozen and paying overnight postage rates, I do temper the coating chocolate. Aaaaanyway, she says her untempered truffles will keep a couple weeks in the fridge or months frozen without blooming.

    Also, bloomed chocolate can still be revived by melting it and following the tempering sequence with fresh seed chocolate, no? I’ve always thought being a chocolatier would be the way to go since you don’t have to put those Easter bunnies or Christmas Santas or Valentine hearts on sale after the holidays when you can just melt them down and start all over again. Plus you get to lick your fingers. ;>

    • joepastry says:

      Ha! I like that.

      Refrigeration definitely will reduce fat bloom in the short term. That’s an interesting technique about coating truffles with untempered chocolate. She’s the expert and I’m not, but from what I know it’s generally tempered chocolate that has the sharper melt point since the crystals are more uniform. Maybe she simply prefers the softer texture. I dunno, as I said, she’s got a lot more expertise in this realm than I do. But bloomed chocolate can indeed be remelted as if nothing ever happened…though I’ll caution that if it’s been in the refrigerator or freezer for a long time there’s a good chance that the fats have picked up off flavors. Another good reason to use the cheap stuff — no need to freeze because there’s always more where that came from! ;)

      - Joe

  3. Linda says:

    I was thinking refrigeration WOULD make the chocolate bloom. Maybe I’m thinking freezing. I remember years ago (YEARS) working in a concession area of a Winston Cup Speedway during the summer. It was so hot the candy bars were melting so we tossed them in the ice area to firm up again and the owner of the stand told us not to do that because they would turn white (weird what you remember years later!)

    You can usually find the Candiquik kind of thing in most groceries usually labeled almond bark or candy coating in the baking aisle. Unless I’m wrong about the almond bark but I’ve always been told that’s the same thing.

    • joepastry says:

      Either one works about the same in my experience…and I use those often!

      Cheers,

      - Joe

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