The texture of what we eat is to a great extent determined by how we prepare our food, but it is also affected by the many natural processes that take place in the raw ingredients as they ripen, mature, age, ferment, and break down in a number of other ways. These processes are responsible for the inherently transitory nature of all life, and hence, the perishability of food. They serve to convert many of the substances that make up the raw ingredients into nutrients that we can more easily absorb and that supply us with the energy we need.