Starch.—Starch occurs in the form of granules. See Fig. 39. In boiling water, the granule expands and finally bursts, and frees the content, the pure starch, and the whole mass thickens.
Boiled with an acid the starch is changed to dextrin, a substance resembling a gum, and the mixture becomes thin; and this process continued changes the dextrin to dextrose.
With intense “dry” heat, as in toasting, the granule expands and opens, and the contents change to dextrin. Continued heat reduces the starch to pure carbon. The brown color and pleasant flavor in toast are a stage on the road to carbon.
Sugar.—Sugar first melts with heat, then begins to decompose, giving off water. This is also a stage on the road to pure carbon. Caramel, a familiar flavor, is sugar in the brown stage, with the water partly driven off.
The art in applying intense heat to fat, starch, and sugar is to know the stopping point,—to reach the “brown taste” and stop short of the “burnt taste.”
Mineral matter.—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.
The technique of food preparation.—From the moment the food materials enter the kitchen until the unusable portions are destroyed or carried away, there is a best way of working with them at each step, and the sum of these may be said to make a good technique. This technique will include cleanliness first and foremost, then skill in the use of tools, judgment in managing cooking apparatus and in applying heat in cooking processes, and accuracy and rapidity of execution. It will also include or add to itself the æsthetic element, the fine art of flavoring, the dainty garnishing of a dish. Moreover, this technique is the method of putting into practice some basic, scientific principle. To illustrate: