part of the most valuable ingredients. If much fruit and salad vegetables are included in the diet, it may not be necessary to consider the loss of mineral salts ; but if it is desired to preserve them, the potato should be cooked in its jacket. This means that the potato is not quite so white, but there is no special reason why a perfectly white potato should be demanded. If potatoes are put on in cold water to boil, the same effect as soaking is obtained. Most of the mineral matter and protein, and some of the starch are lost. If, instead, the potatoes are placed in boiling water, the protein is coagulated quickly and less of it escapes. Most of the mineral salts are still dissolved by the water and so lost, since potato water has rather too strong and disagreeable a flavor to be palatable and is usually thrown away. Potatoes may be steamed with little loss of nutriment, or baked, in which case practically nothing is lost but water. Potatoes are cooked partly to hydrate the starch, and partly because the expansion of water into steam means the breaking of the cellulose walls of the cells, whereby the contents become more readily digestible. Probably the chief reason is the improvement of flavor. Since potatoes contain a small amount of cellulose, com- pared with most other vegetables, they are digestible, and there is comparatively little difference in their digestibility as a result of different ways of cooking. A mealy potato seems to be more digestible than a soggy or waxy one, probably because it is better broken up, and so the diges- tive juices can get at it better. Potatoes have long been classed as a starchy food, and most books state that there is so little protein present that it need not be taken into account. Max Rubner, in a recent paper, states that the protein present is of such a character and amount as to form a balanced ration, if it were possible to consume the necessary bulk to supply the needed energy. Potatoes 38 FOOD STUDY are so bulky, on account of the large amount of water present, that they cannot serve as a sole food. Sweet potatoes differ botanically from white in that they are thickened roots instead of stems. Chemically, they contain about nine per cent less water, and more carbo- hydrate. Most of this additional carbohydrate is sugar, which accounts for the sweet taste. Sweet potatoes grown in different regions vary greatly in the amount of sugar, those grown in the south containing a larger per- centage than those in the north. There is so little differ- ence in food value between sweet and white potatoes that they may be substituted for one another in the diet. REFERENCES U. S. Dept. of Agriculture. Farmers' Bulletin No. 244. "Cooking Quality of Potatoes." Farmers' Bulletin No. 256. "Preparation of Vegetables for the Table." Farmers' Bulletin No. 295. ' 'Potatoes and other Root Crops as Food." Office of Exp. Station Bulletin No. 43. "Losses in Cooking Vege- tables." "Comparison of the Digestibility of Potatoes and Eggs." QUESTIONS 1. Why should not potatoes be tightly covered while boiling? 2. How should they be cared for when done ? 3. Why are new potatoes more often cooked in their skins or jackets than old potatoes ? 4. When do new potatoes come into market ? 5. What is the average cost of potatoes ?

AI-modernized reading of the original text

part of the most valuable ingredients. If much fruit and salad vegetables are included in the diet, it may not be necessary to consider the loss of mineral salts ; but if it is desired to preserve them, the potato should be cooked in its jacket. This means that the potato is not quite so white, but there is no special reason why a perfectly white potato should be demanded. If potatoes are put on in cold water to boil, the same effect as soaking is obtained. Most of the mineral matter and protein, and some of the starch are lost. If, instead, the potatoes are placed in boiling water, the protein is coagulated quickly and less of it escapes. Most of the mineral salts are still dissolved by the water and so lost, since potato water has rather too strong and disagreeable a flavor to be palatable and is usually thrown away. Potatoes may be steamed with little loss of nutriment, or baked, in which case practically nothing is lost but water. Potatoes are cooked partly to hydrate the starch, and partly because the expansion of water into steam means the breaking of the cellulose walls of the cells, whereby the contents become more readily digestible. Probably the chief reason is the improvement of flavor. Since potatoes contain a small amount of cellulose, compared with most other vegetables, they are digestible, and there is comparatively little difference in their digestibility as a result of different ways of cooking. A mealy potato seems to be more digestible than a soggy or waxy one, probably because it is better broken up, and so the digestive juices can get at it better. Potatoes have long been classed as a starchy food, and most books state that there is so little protein present that it need not be taken into account. Max Rubner, in a recent paper, states that the protein present is of such a character and amount as to form a balanced ration, if it were possible to consume the necessary bulk to supply the needed energy. Potatoes are so bulky, on account of the large amount of water present, that they cannot serve as a sole food. Sweet potatoes differ botanically from white in that they are thickened roots instead of stems. Chemically, they contain about nine per cent less water, and more carbohydrate. Most of this additional carbohydrate is sugar, which accounts for the sweet taste. Sweet potatoes grown in different regions vary greatly in the amount of sugar, those grown in the south containing a larger percentage than those in the north. There is so little difference in food value between sweet and white potatoes that they may be substituted for one another in the diet. U. S. Dept. of Agriculture. Farmers' Bulletin No. 244. "Cooking Quality of Potatoes." Farmers' Bulletin No. 256. "Preparation of Vegetables for the Table." Farmers' Bulletin No. 295. ' 'Potatoes and other Root Crops as Food." Office of Exp. Station Bulletin No. 43. "Losses in Cooking Vegetables." "Comparison of the Digestibility of Potatoes and Eggs." 1. Why should not potatoes be tightly covered while boiling? 2. How should they be cared for when done ? 3. Why are new potatoes more often cooked in their skins or jackets than old potatoes ? 4. When do new potatoes come into market ? 5. What is the average cost of potatoes ?

Food study