The characteristic aroma and taste

The characteristic aroma and taste of coffee only appear later and are developed by the high temperatures to which they are subjected during the course of the process known as roasting. Temperatures are raised progressively to about 220-230�C. This releases steam, carbon dioxide, carbon monoxide and other volatiles from the beans, resulting in a loss of weight of between 14 and 23 per cent. Internal pressure of gas expands the volume of the coffee seeds from 30 to 100 per cent. The seeds become rich brown in colour; their texture becomes porous and crumbly under pressure. But the most important phenomenon of roasting is the appearance of the characteristic aroma of coffee, which arises from very complex chemical transformations within the beans. The coffee, on leaving the industrial roasters, is rapidly cooled in a vat where it is stirred and subjected to cold air propelled by a blower. Good quality coffees are then sorted by electronic sorters to eliminate the seeds that roasted badly. The presence of seeds which are either too light or too dark depreciates the quality.