Not just heating, even simple cutting/mincing of the food promotes oxidation that can significantly influence the composition of food. On the other hand some p

Not just heating, even simple cutting/mincing of the food promotes oxidation that can significantly influence the composition of food. On the other hand some processing like canning of fresh food can actually help preserve the good stuff compared to whole food that's refrigerated or otherwise stored over longer periods of time. Processing also can increase the bio-availability of many ingredients, which can sometimes be a good thing, or in case of sugars not so good.