The "ash" remains for the most part unchanged by heat, but may be lost in the water in which vegetables and meat are cooked if the water is thrown away.

Vegetable fiber is softened by heat and moisture, and the protein, starch, fat, and sugar are freed, making them available for our digestion and nutrition.

Meat fiber softens at a low temperature, that is, below the boiling point of water, with moisture; continued intense heat shrinks and hardens it. A tender steak fried with fat in a hot pan will soon resemble sole leather.