Beans from the cacao tree, the source of all chocolate, vary in both flavour and aroma. During the stages of fermentation, roasting and grinding these different qualities develop further and imbue the resulting chocolate liquor with a unique character. The chocolate liquor, which is made up of both cocoa solids and cocoa butter, is then transformed into your favourite block with the addition of sugar, milk or perhaps other flavourings. Top-quality chocolate has a high cocoa-solid content and is not overly sweet. Chocolate tasters determine the quality of chocolate according to its appearance, aroma, 'snap', texture, flavour and aftertaste. If chocolate has a milky bloom over its surface the cocoa butter has separated from the solids, but it is still edible and the bloom disappears on melting.

1. Cooking chocolate
Cooking chocolate can be dark (bittersweet or semi-sweet), milk or white and its quality is determined by the amount of cocoa butter and cocoa liquor it contains. Couverture is preferred for its silky finish.

2. Flavoured chocolate
Popular eating chocolates are filled or flavoured with such ingredients as caramel, orange, mint, marzipan or alcohols, or toasted nuts or dried fruits. The base chocolate can be of a greater or lesser quality, and may be either milk or dark. Occasionally white chocolate is also flavoured, such as with vanilla seeds.

3. Cocoa powder
Cocoa powder is made by removing most of the cocoa butter from chocolate liquor, then drying and grinding to a powder the bitter cocoa solids that remain. There are two types of unsweetened cocoa: natural and Dutch-processed. Dutch cocoa's strong flavour is preferred by many cooks.

4. Dark chocolate powder
Sweetened cocoa is sold as either drinking chocolate or chocolate powder that is ready to serve as a hot or cold drink with water or milk. As with cocoa, some chocolate powders are labelled according to their fat content to reflect the amount of cocoa butter (indicating flavour) they contain.

5. Sugar-free chocolate
This type of chocolate is sweetened with maltitol to increase its appeal to diabetics and people with weight problems - but it's still high in saturated fats and energy, so keep it in the 'treat' category!

6. Plain eating chocolate
Eating chocolate is 'conched' or massaged by a special machine that blends and smooths the ingredients. The process can take up to three days for top-quality chocolate, and it contributes to both the flavour and a rich 'mouth-feel'. The higher the cocoa solids and more bitter the flavour the more beneficial antioxidants you will be eating - so it's healthy, too.

Heating hint
To melt chocolate, place in a heatproof bowl and set over a pan of just-simmering water. If any water or steam comes into contact with the chocolate, it will 'seize'. Adding a little vegetable oil may resolve the problem.