Peter Barham explains: “Cooking food increases the range of foods we can eat. Foods which would otherwise be indigestible can be made edible. For example we cannot digest raw potatoes, since the starch is in a form our stomach is not capable of processing; however, by heating to a high enough temperature the starch is altered, and it becomes edible. Some foods may contain toxins (e.g. pork), these toxins can often be destroyed by the application of heat. Thus cooking food can lead to a reduced risk of food poisoning.
Cooking can also change the texture of foods; for example the ‘tenderising’ of some meats can make otherwise unappetising food more appealing, and increase the available food supply.
Further, …cooking often leads to chemical reactions that change the flavour of foods by breaking down large molecules (which we cannot taste) into smaller molecules that we can taste.”
Ref: p.37 Peter Barham (c2001) The Science of Cooking. Springer-Verlag: Berlin