Microbes and food 1. Menu - you are what you eat
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Cocoa pods growing photo
Picture 1.21a Cocoa pods growing on their tree.
1.21 Chocolate
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What is it?
Chocolate is made from cocoa beans which form inside pods on trees. They have a high proportion of sugar and a hard outer coating. The pods are harvested and cut open. The beans are heaped onto banana leaves and left to ferment.
How is it produced?
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The contents of the cocoa pods are scooped out and set in heaps where microbes occurring naturally on the plant cause a fermentation which lasts for 7 days. The beans are turned daily to let in air. The fermentation process is complex and involves a succession of microbes, starting with yeasts, continuing with bacteria and finishing with moulds. Over 30 different bacteria have been found in fermentations. The alcohols, acids and heat formed during fermentation induce complex biochemical reactions inside the beans.

Unfermented beans do not produce chocolate flavour and scientists have been unable to replicate the complicated biochemistry that takes place on the farm in the laboratory. Chocolate is a food which can only be made with the help of microbes.

After the beans have fermented they are dried and taken to the processing plant for roasting and kibbling (broken into pieces). The broken shells are removed and the small pieces left called nibs are reduced to a thick liquid which contains about 55% cocoa butter. About half the cocoa butter is removed by pressing and used to make chocolate bars. The rest is ground up to make cocoa powder.

Chocolate mousse photo
Picture 1.21b Mousse is one food that can be flavoured with chocolate.
How does it spoil?
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Chocolate does not spoil due to its low water content, although moulds can develop inside the packaging if it gets damp. The same is true of cocoa powder. Chocolate is an ingredient of many confectionery products and desserts which can be spoiled by different micro-organisms according to their content. The fillings of chocolates can sometimes ferment due to yeast growth – leading to the sweets bursting.
Chocolate bars photo
Picture 1.21c It is important that chocolate is packaged hygienically.


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Can it be harmful?
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Food poisoning due to eating chocolate has been reported. Salmonella has been found in cocoa powder where it can survive for long periods, but most cases are due to contamination of the product during processing and packing. It is therefore important to use the highest standards of hygiene and quality assurance during chocolate and confectionery manufacture.