Sixty to 85 percent of a mature fresh squash fruit is edible, as compared to over 95 percent edibility in immature fruits. The edible portion of a pepo, which is 85 to 95 percent water by weight, is lacking in most nutrients, particularly protein (0.5 to 2.0 percent) and fat (less than 0.5 percent). Carbohydrates are more concentrated in mature fruits (up to 15 percent of the fresh edible portion) than in the tender fruits of the summer squashes (less than 5 percent). Likewise, calories per 100 grams of edible fresh-weight flesh range from 10 to 25 in summer squashes versus 20 to 45 in the mature fruits known as pumpkins and winter squashes.
The most significant dietary contribution of the pepo is the relatively high concentration of carotenes, the precursors of vitamin A, in cultivars with deep yellow to orange flesh (see Table II. C.8.5).
Table II. C.8.5. Mineral and vitamin content of young fruits (represented by the summer squashes of Cucurbita pepo), mature fruits, leaves, and growing tips (including C. maxima, C. moschata, and C. pepo), and ground seed meal (a mixture of C. pepo and C. maxima); values are per 100 grams'of dry seed meal or, in the case of the other structures, of the fresh-weight edible portion
AWhitaker and Davis (1962); bTindall (1983); cMartin (1984); dOomen and Grubben (1978); eLazos (1986).
Particularly well studied and rich in these and other nutrients are the ‘Butternut’ and ‘Golden Cushaw’ cul-tivars of C. moschata and various “hubbard” and “delicious” squashes of C. maxima. As a source of vitamin A, these winter squashes compare with sweet potatoes and apricots. Although the raw flesh is higher in vitamins, a half cup of cooked mashed winter squash provides 91 percent of the U. S. Recommended Dietary Allowance (RDA) of vitamin A, 16 percent of the recommended vitamin C, 12 percent of the recommended potassium, 1.7 grams of dietary fiber, low sodium, and only 40 calories. In addition to the carotenoids, squashes are good sources of other compounds with cancer-fighting potential, including flavonoids, monoterpenes, and sterols.
For some nutrients the best source is not the fruit but other parts of the squash plant (see Table II. C.8.5). Leaves are richer in calcium, growing tips provide more iron as well as higher levels of vitamin C and the B vitamins, and seeds contain various minerals including potassium, magnesium, copper, and zinc. Although the nutritional content of flowers has not been studied, the orange petals are undoubtedly rich in carotenes.
Seeds are the most nutritious part of the plant, containing 35 to 55 percent oil and 30 to 35 percent protein by weight. In fact, the naked seeds of ‘Lady Godiva’ are very similar in agricultural yield and nutritional content to shelled peanuts.
The edible semidrying oil of squash seeds is dark brown with a green tint and a nutty odor. About 80 percent of the oil consists of unsaturated linoleic (40 to 50 percent) and oleic (30 to 40 percent) acids. The dominant saturated fatty acid, palmitic acid, accounts for about 13 percent of oil composition. As with other oilseeds, proteins in squash seeds are rich in nitrogen-containing amino acids such as arginine but lacking in lysine and sulfur-containing amino acids. These proteins are packaged primarily in globulins called cucurbitins. Whereas the testa is highly fibrous, carbohydrates in the decorticated seeds are limited to cell wall cellulose, phytic acid, and a minimal amount of free sugars; starch is absent. Ground seeds (including the testas) are good sources of minerals, particularly potassium, phosphorus, and magnesium (see Table II. C.8.5).
Deena S. Decker-Walters Terrence W. Walters
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World History
