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March 15, 2006

Turning a cocoa bean into something useful

Cocoa was discovered by the Olmec an ancient people living in Southern Mexico between 1500 and 400 BC. They were the first to cultivate the cocoa tree. Already 600 BC hey were known for a drink called 'kakawa'. Cocoa beans made their first documented appearance in Europe at the court of Prince Philipp of Spain in 1544. But it still took a few hundred years to turn the cocoa beans into the delicious chocolate we know today

The process of making chocolate bars is incredibly complex. The fruit of the cocoa tree is melonlike and between 10 to 30 cm long. Each fruit contains 30 - 50 cocoa beans, exactly the amount needed for a 100 g chocolate bar. After picking the fruits are opened and the beans taken out, spread in the open and covered by banana leaves. After a few hours a complex fermentation process starts. During the first 24 hours yeast cells decompose glucose to ethanol, afterwards lactobacilli take over and produce lactic acid. This reaction is exothermic (producing heat) and raises the temperature of the mixture to 37 degrees Celsius. This gives another type of bacteria the chance to have a go at the ethanol and lactic acid turning it into acetic acid. The temperature raises further to over 50 degrees Celsius and eventually the fermentation process stops. The beans are then dried in the open for about two weeks losing most of their lactic and acetic acid content during this time. Afterwards they are ready for shipping.

During the fermentation process quite a number of 'aroma precursors' are formed. When the cocoa beans arrive at the chocolate plant they are roasted for 1-2 hours. The roasting lets the 'aroma precursors' react with sugars turning them into the characteristic chocolate flavours. Quite a number of complicated chemical processes take place during the roasting of the cocoa beans which I don't want to go into detail here. The result, however, are dark brown, lovely smelling cocoa beans.

After the roasting the shells of the cocoa beans are removed and the beans are grounded. Then the natural fat of the beans, called cocoa butter, is extracted, leaving cocoa powder behind. In 1847 the English manufacturer Fry & Sons created the first chocolate bar from grounded cocoa beans, sugar and cocoa butter called 'Chocolat Délicieux à Manger'. Cocoa butter has a melting point between 34 to 38 degrees Celsius rendering chocolate a solid at room temperatur that readily melts in the mouth.

The real step forward towards 'high quality' chocolate was made possible by the Swiss Rudolphe Lindt (1855-1909) who invented the 'conche'. The first conche was a device made of granite in which the grounded cocoa beans were kneaded together with other ingredients such as sugar and cocoa butter by two granite rollers. The friction was sufficient to heat up the mixture beyond its melting point. In the conche the cocoa bean particles are reduced to sizes below 20 microns. The tongue is not capable of detecting individual particles of this size. In other words: before the invention of Rudolphe Lindt chocolate felt like sand in your mouth.

Besides reducing the size of the cocoa bean particles the conching process also coats the cocoa bean fragments with a layer of cocoa butter. Flavours from the cocoa beans diffuse into this fat layer thereby enhancing their effectiveness. Since the 1930's lecithin is also added during the conching process. Traces of lecithin reduce the viscosity of the chocolate considerably.

Cocoa butter has a fascinating property: it is polymorphic, i.e. it crystallises in six different forms (I - VI) The chemical composition is always the same but the arrangement of the fat molecules in the crystal is different in each form. Gourmets will only accept chocolate of type V which is the only one that has a glossy surface, the right degree of hardness and melts in your mouth. Type VI is the thermodynamically most stable one but its surface is dull and its melting point at 36.3 degrees Celsius lets it only melt reluctantly in the mouth. If you keep type V too long or too warm it will eventually turn into type VI. Type VI is softer than type V reminding you of biting into a wax candle. The different types are achieved by heating and cooling the chocolate in the right way - another very complex process.

Chocolate contains quite a few useful things like antioxidants and minerals. It does not contain cholesterol but a lot of sugar. After reading through all this I hope you are still able to enjoy your piece of chocolate now and then and perhaps will from now on also appreciate the work of countless scientists, engineers and manufacturers who put so much effort into turning the bitter tasting cocoa bean into this heavenly product...

Posted by Mausi at March 15, 2006 09:42 PM

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