Experimental cookery

Some investigations on potato quality. It is rather commonly be- lieved that to have mealy potatoes the starch content should be high and that the swelling and bursting of cell walls during cooking produces the white, fairly dry, flaky appearance. Sweetman states that the starch grains do not swell sufficiently to burst but the cooking renders the starch granules readily separable. That ease of cell separation is one of the causes of mealiness is unsubstantiated by other investigators. Whittemore and Juschke decided that potatoes were more mealy when fertilized with a high rather than a low quantity of potash (potassium carbonate). Cobb states that the parts of the tuber having the greatest concentration of starch are mealiest when cooked. The rank in descending order is cortex, external medulla, and internal medulla. Cobb in a series of investigations covering 5 years found that baking gave more mealy potatoes than boiling. 134 FRUITS AND VEGETABLES Baked potatoes often lost 25 per cent of their weight by evaporation, whereas boiled ones lost none. Environmental factors. Cobb concluded that if proper cultural con- ditions were given any type of soil may grow good potatoes. His studies showed that temperature during growing and variety were the most important factors affecting potato quality. A low-average temperature favored better quality. This suggests that one reason why Maine and Idaho are noted for their potatoes is the low-average temperature during growth of the potatoes. Small, immature, or ill-shaped tubers were ob- served to have poor quality. Stevenson and Whitman state that a variety producing good-quality potatoes under certain conditions may produce poor ones under other condi- tions, but a good-cooking variety tends to maintain better quality over a wider range of conditions than a poor-cooking quality. Starch granules. It is possible that two factors determining whether a potato produces a mealy or waxy consistency when cooked are the size of the starch granule and its phosphorus content. See Starch, Chapter XL Large granules swell and gelatinize at a lower temperature than small granules. Thus, potatoes giving a dry, mealy texture may have a compara- tively larger percentage of large granules. Smaller granules are supposed to have a higher phosphorus content than large ones, and the paste-forming qualities of starch are increased when the starch is combined with phos- phorus. If paste-forming qualities mean increased adhesiveness, then waxy potatoes may have either smaller granules or a higher phosphorus content or both. Storage temperature. Wright et al. found that the storage tempera- ture affected the quality of the cooked potatoes. They stored Irish Cobbler potatoes harvested August 3 for 8 weeks at the following temperatures: ^2"", 36°, 40°, 50°, 60°, and 70°F. In general potatoes stored at 40° were considered fair in quality when cooked; those from storage at 32° and 36° were poor; those from 50° good; those from 60° very good, and those from 70° good. The baked and boiled products from potatoes stored at 40° were slightly sweet and watery; those from 36° storage were inclined to be soggy or watery, with a distinctly yellow color and sweet flavor; those from storage at 50°, 60°, and 70° possessed no undesirable sweet flavor and were of mealy texture and cream in color.