 To destroy harmful bacteria present in the food  To preserve the food  To provide variety in the diet; e.g. potatoes can be fried, boiled, creamed, roasted.  To enhance flavour e.g. roasting meat develops extractives which add to the flavour.  To destroy harmful bacteria present in the food  To preserve the food  To provide variety in the diet; e.g. potatoes can be fried, boiled, creamed, roasted.  To enhance flavour e.g. roasting meat develops extractives which add to the flavour.