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Cooling Down with Chocolate – and why you shouldn’t Store Chocolate in the Fridge

By Cocoa Runners  ·  16th August 2020  ·  The Science of Chocolate

As we were melting in the UK’s mini heatwave, it seemed like a great time to explore the importance of heat in chocolate crafting.  

Before we delve into the intricacies of roasting, grinding, conching and tempering chocolate (all of which rely on heat to work their magic on cocoa beans), some good news: savouring Craft Chocolate will cool you down.

Craft Chocolate is one of the very few solid foods that melts at just below human body temperature (arguably it’s unique here: butter melts at room temperature and ice cream melts straight out the freezer). This means that it melts in your mouth (or in your hands if you keep it there for too long).

As chocolate transitions from solid to liquid in your mouth, it absorbs heat from your body and thereby cools you down.  It is also this melting that releases all the volatiles and aromas in the chocolate.  And these volatiles and aromas are what gives Craft Chocolate its spectacular flavours (join a Virtual Tasting to find out more – and witness how many unprompted mentions of “cooling” we receive).

So as you read on to celebrate the impact of heat in the many stages of chocolate crafting, please make sure you have a morsel of chocolate to savour and help you cool down.

ROASTING

As with Specialty Coffee, cocoa beans, once they’ve been fermented and dried, need to be roasted. (For a discussion on a few exceptions who don’t roast (like Raaka), and the nonsense that is “RAW” chocolate, or the radically different approach taken by mass-produced chocolate makers, please see this blog post.)

And again, like coffee, roasting imparts flavour through a variety of different chemical reactions – the most important being the Maillard Reaction and Caramelisation.  Part of the skill of any Craft Chocolate maker is figuring out the right sort of roast (i.e. how long and at what temperature) and even what sort of roaster (i.e. convection versus drum coffee roaster, etc.) to use.  The differences are dramatic — all sorts of different notes are revealed; earthiness, nuttiness, spices, flowers and more (this is caused by heat releasing pyrazines, phenyls, thiazoles and phenyalkalanals in the cocoa beans).

For a couple of examples of how much impact roasting can have, try some of the bars crafted by Rob and Amy from Fresco – they sell side by side bars crafted from the same beans but roasted either “Light”, “Medium” or “Dark”.  Or try Conexion’s “virgin” and “medium roasted” bars for even more dramatic showcasing of the impact roasting time and temperature has on the vegetal, woody tastes of her Arriba Nacional beans from Ecuador.  The difference is staggering.

GRINDING AND CONCHING

Post roasting, the beans are winnowed (the shells are removed) and then the “nibs” are ground and conched. 

We’ve been grinding the roasted cocoa nibs into a paste and then mixing this paste with water and spices to make “drinking chocolate” for at least five thousand years. Just under two hundred years ago we started to consume chocolate bars when Joseph Fry discovered that by adding cocoa butter to this drinking chocolate paste he could make solid chocolate bars.  However these bars were gritty and texturally very different to today’s chocolate bars.

The two inventions which really catapulted chocolate into the mainstream were conching by Rodolphe Lindt and the parallel creation of milk chocolate by Daniel Peter and Henri Nestle in the 1870s and 1880’s.  These two inventions gave rise to the smooth, moreish, flavourful bars that we all love today.  And again, heat plays a key role. 

Conching is so named because the early machines looked like conch shells.  Essentially they involve “sloshing” the ground cocoa beans (which have become a liquid) against a solid surface under high temperature (45-80 degrees celsius).  And this heat and “sloshing” both reduces bitterness and astringency in the chocolate, and also brings out additional flavours in the cocoa beans.  Think of it similar to the way that bakers knead bread before baking it (except in the case of chocolate it’s the other way round … i.e. roasting / baking then conching / kneading)

To make milk chocolate, you need to add dehydrated milk powder as you grind and conche the chocolate.  And heat again plays a critical role in “caramelising” the milk to create sweetness. Dark Milks (i.e. a milk bar containing over 50% cocoa solids) often contain less added sugar than many 70%+ Dark Chocolate Bars, yet they taste far sweeter and creamier — see these bars by Soma and Georg Bernadini.  (And if you want to know why American milk chocolates taste so “different”, and the link to parmesan, please do join a Virtual Tasting.)

TEMPERING

Once the chocolate has been ground and conched, the final stage before the bars are wrapped again involves heat – Tempering.

Tempering involves raising and lowering the heat of the liquid chocolate so that it becomes a stable solid product that can be wrapped.  Well-tempered chocolate “melts in the mouth”, snaps with a clean break, and has a glossy texture.  Despite the magical nature of turning a liquid into a stable solid, and the difficulty of the task involved, we don’t really have a great term to describe this – we just call it “Crystal Structure 5”. (Technically what is happening here is that cocoa butter fat can take one of six crystal structures, but only one, Crystal Structure 5, melts in your mouth.)

And when chocolate goes through significant temperature changes, the cocoa butter is liable to change its crystal structure. This is why you don’t want to store chocolate in the fridge, as you will “retemper” the chocolate. And when chocolate “retempers”, it changes to Crystal Structure 6.  And it will “bloom” (i.e. some of the cocoa butter will come to the surface, giving it a white matte look).  And the chocolate won’t melt in your mouth.  And it has a terrible snap.  But you can cook with it, or make drinking chocolate out of it.  

The bottom line is: don’t let your chocolate melt in the sun (or in your pocket).  And NEVER, EVER put it in the fridge (for more on how to store chocolate, please check this handy page).

DIVERSITY OF FLAVOUR THANKS TO HEAT

Part of the magic and alchemy of Craft Chocolate is the way that heat, via roasting, grinding, conching and tempering, brings out all sorts of flavours in a chocolate bar that literally “melts in your mouth”.  And it’s the extraordinary complexity involved in all the above steps that creates incredible diversity of flavour — over 800 different flavour notes according to the inestimable Harold McGee (even more than wine).  Growers, sourcers and cooperatives like Bertil Akesson, Kokoa Kamili, Zorzal, PISA, etc. sell to hundreds of different makers — and each of these makers crafts bars with radically different flavours because of the different “heats” they choose when roasting, conching and tempering.  See below for two dark milk bars crafted in Germany (Georgia Ramon) and Canada (SOMA) from the same beans to experience this diversity.

So given that savouring Craft Chocolate will also cool you down, we urge you to try a few of the bars below: