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My friend (who lives in a warm, humid climate) often has issues with chocolate, due to the formation of a light-colored coating on it. I believe it is just chocolate bloom, but she thinks it's mold and should trash the chocolate. Visual inspection alone does not seem sufficiently precise to identify which of these has happened.

Is there a reliable way to test which one is the case? i.e., re-heating it, or trying to remove the coating with a knife, or some other technique which does not require using a microscope?

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It is is almost impossible for chocolate to mold as it doesn't have any moisture, required for mold growth.

There are two types of bloom:

Sugar bloom -- wipe the chocolate with a wet finger, it will dissolve.

Fat bloom -- wipe the chococolate with a dry finger, it will feel waxy or greasy

Either tends to look like a chalky coating, not very thick, definitely not fuzzy (like mold).

  • Indeed, that is a simple and convincing technique. So if after wiping the finger I still have some powdery substance which does not dissolve in water, then it's certainly mold. Right? Or could it happen that the mold might eventually dissolve? I'm expecting it should feel a bit like a Camembert cheese... – anol Aug 28 '13 at 16:44
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    The chances that is mold are astonishingly small, as chocolate is very inhospitable to molds, unless the chocolate was stored in very improper conditions. I don't know what mold would feel like, since I have never had it happen. I suspect it will be fuzzy as most mold fruiting bodies have that appearance. It may also be splotchy in appearance. Googling for "moldy chocolate" images didn't provide much credible information. – SAJ14SAJ Aug 28 '13 at 16:50
  • I believe that when it happened to my friend, it was because it had been stored in a plastic container in the fridge (which was maybe not entirely clean). This, or maybe forgetting the container on the bottom of the fridge for several months... – anol Aug 28 '13 at 17:19
  • That is a likely scenario for sugar bloom... – SAJ14SAJ Aug 28 '13 at 17:22
  • Chocolate that has been badly tempered is more susceptible to bloom, as is chocolate that has melted in it's wrapper. – silves89 Aug 30 '13 at 14:31
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Chocolate cannot grow mold. Sugar bloom or fat bloom are the only things you'll see happening on chocolate. This only happens when the chocolate is improperly tempered or improperly stored. May not look pretty or taste good, but it's not moldy. You can re-temper it as long as it's just plain chocolate (no filling, nuts etc).

  • Please do not repeat other answers – user34961 Mar 12 '18 at 7:25
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    @JanDoggen : They didn't. You could say that they've combined the comments from another answer, but they've also added the note that you can retemper bloom, which I would assume is another test. (if it's mold, retempering wouldn't help) – Joe Mar 12 '18 at 14:15
  • Chocolate can grow surface mold if it's improperly stored in a humid enough climate that will supply the moisture that chocolate lacks. The type of mold that grows in chocolate is usually medium green and fuzzy, and it grows in small spots, very consistent with Aspergillus cultures – Juliana Karasawa Souza Sep 24 '19 at 17:56

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