As vegetable food is eaten both raw and cooked, the pupils should be asked to decide when cooking is necessary and what they wish it to accomplish.
There are only two substances in vegetable food which will require cooking, and these are:
1. Cellulose, if it be hard or tough
2. Starch, if it be present.
The pupils have found in their experiment with the potato water, that starch cooks quickly, hence the time of cooking will depend altogether on the texture of the cellulose. When the cellulose is softened at the centre, the last part which the heat reaches, the vegetable or fruit will be cooked.
If the food is cooked in water by boiling or simmering, much of the substance will pass into the cooking water. As the cell walls become softened, they allow the cell contents to partially pass out and the cooking water to pass in to fill the space. If the food is long in cooking, the water may have more value than the vegetable, and it should not be thrown away. It may be used in two ways—as a basis for a sauce or a soup.
GENERAL RULES FOR COOKING VEGETABLES
Note.—As the principles in the general rules have been taught, these rules may be dictated to the class.