By Harold McGee
Caramels and their relatives are generally noncrystalline candies that contain milkfat and milk solids, usually in the concentrated form of sweetened condensed milk. (Cheap versions are made with milk powder and vegetable shortening.) They are chewy rather than hard, and wonderfully mouthwatering because chewing liberates droplets of butterfat from the sugar mass. Their chewiness comes from a lower cooking temperature and so a higher moisture content than hard candies, a large proportion of corn syrup, and the presence of milk casein proteins. The characteristic caramel flavor develops from the milk ingredients and reactions between these and the syrup sugars during the cooking. In Britain, butter for toffee was often stored to develop some rancidity (from free butyric acid), which produced a desirably stronger dairy flavor in the finished candy. (American chocolate manufacturers have done much the same thing; see box). The higher the fat content, the less these candies stick to the teeth.