Why refrigerated chocolate tastes better

The difference of opinion when it comes to whether chocolate tastes better out of the fridge or not has caused many a discussion between me and my peers, and has almost torn friendships apart (not really); but after one of my lecture courses from last semester, I can finally definitively say that chocolate DOES in fact taste better from the fridge.

First, a little background. This is all to do with a phenomenon known as polymorphism, which is the ability for a solid to exist in more than one crystal structure. Each crystal structure is called a polymorph, and each polymorph has its own set of distinct properties.

The main ingredient in chocolate, cocoa butter, has six polymorphs which can be distinguished between each other by measuring their melting points:

Polymorph I, 16-18 degrees
Polymorph II, 22-24 degrees
Polymorph III, 24-26 degrees
Polymorph IV, 26-28 degrees
Polymorph V, 32-34 degrees
Polymorph VI, 34-36 degrees

Polymorphs I – IV are not suitable for making chocolate since they are too sticky and unstable at room temperature. Polymorph VI is the most stable, but tastes bland and is too brittle. Polymorph V is the ideal form for eating (but of course, sod’s law dictates that it’s the hardest to manufacture).

This is great, I hear you saying, but why does this mean I should keep my chocolate in the fridge? Well… at room temperature, the fatty molecules in polymorph V have enough energy to slowly (days/weeks scale) convert to polymorph VI. This transformation in in the crystal structure is facilitated by the vibrational energy stored in the molecules which allow the molecules to wriggle about and realign with each other. This can be stopped by keeping your chocolate in a cool, dark place (i.e., the fridge!!) to make sure the molecules don’t have enough vibrational energy to convert to polymorph VI.

fat blooms

Fat blooms in chocolate

You then might ask how you can tell this has happened? The change in crystal structure is usually accompanied by something called ‘fat bloom,’ which is where the chocolate begins to look dusty, and pale spots appear on the surface as shown in the attached image. We’ve all been there (you’re incredibly lucky if you haven’t). It’s off putting, but still safe to eat. It happens because of partial melting in the solid which cases the fats within it to rise to the surface. It’s this strange occurrence that leads me to believe that keeping my chocolate in the fridge is in fact the correct way to keep it, and also why all the chocolate I bought on my exchange year in Australia just didn’t taste as good as the stuff at home in the UK due to their hotter climate!

Polymorphism doesn’t only have implications on your chocolate, but on almost anything that can crystallise. There are many patent issues with regards to the different polymorphs of drug molecules in the pharmaceutical industry, and a range of other industries. Feel free to comment and ask questions for more detail 🙂

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About ChemistDan

A second year PhD student based in Sheffield researching the reasons behind the molecular blinking phenomenon that allowed for the development of super-resolution optical microscopy.
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14 Responses to Why refrigerated chocolate tastes better

  1. kitanda962 says:

    That’s so cool! I just learnt something ^^
    🙂

  2. Annika Snark says:

    So why does melted chocolate taste so good?

    • ChemistDan says:

      Great question, and you almost had me stumped! But when chocolate is melted it’s no longer in the solid state. In other words, it’s no longer a crystal and the polymorphs have no influence here. When it’s melted, you’re tasting “individual molecules” in bulk instead of an extended network of molecules.
      Hope that answers your question : )

  3. Hi ChemistDan,

    This web page inspired me to make a graphic. As an expert, would you mind giving it a quick look at for factual correctness? If there are any blatant errors on it then I’d be very grateful if you could let me know!

    Here it is: http://jameskennedymonash.wordpress.com/?attachment_id=3588

    Thanks! 🙂

    James

  4. Maria Brandriff says:

    I disagree with you on one point, Dan. I’m a chocolatier and I agree that proper storing in a cool place is important, it is also important to note that if one stores chocolate in the fridge, it has to be wrapped in an airtight way, so that the humidity and odors of the fridge don’t get to it. Furthermore, I beg to differ that refrigerated chocolate tastes better. Refrigerated chocolate BROUGHT TO ROOM TEMPERATURE, indeed, tastes better. Cold blunts taste.

  5. Pingback: The Polymorphs of Chocolate | Compound Interest

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  8. Susan Taylor says:

    As an expat from the UK living in Australia I disagree wholeheartedly re. the hotter climate causing the difference in taste for you. It is to do with the completely different recipe used. It would also make no sense as using your theory our chocolate would taste different in winter.

    I spent the first couple of years here avoiding the chocolate, but now after a few years UK chocolate is inedible to me due to its sweetness. That is to do with change in taste buds according to what you have become used to.

    The top chocolatier here in Australia is called Haigh’s. They are recognised internationally as one of the top quality chocolate makers in the world. I also stand by the comment the chocolatier maker Maria said above. – it is 100% about storage and not necessarily temperature.

    See the 4th part of the caring for your chocolate FAQ from Haigh’s itself: http://www.haighschocolates.com.au/faqs/care/#faq-1

    • Susan Taylor says:

      I forgot to mention the difference in taste with the recipe is to do with different anti-melting agents used and animal fats used here and milk there.

  9. Vasuki Silva says:

    hi Dan,
    i recently saw ur description of polymorphism .i think when chocolate is melted and recooled it does not give its intended taste.because its crystaline structure has been changed..

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