Seed proteins, cucurbit

The Cucurbitaceae are a diverse family of plants that grow in the temperate zone but also thrive in hot and arid regions of the world. The characteristics of cucurbit seed protein and oil were reviewed by Jacks et al. (1972) and by Jacks (1986). He noted a resurgence of interest in... 

Jacks, T.J. (1986) Cucurbit seed protein and oil. Plant Proteins 312, 249-260. 

Research concerning the structure, composition, and usefulness of cucurbit seeds (gourds, melons, squash, etc.) is reviewed. Cytological features are typical of those for oilseeds. Composition-ally, decorticated seeds contain by weight 50% oil and 35% protein. The oil is unsaturated and edible however, certain species contain conju-ated trienoic fatty acids (drying oils). 

Decorticated cucurbit seeds contain by weight about 35% protein. Traditionally, seed proteins are classified as globulins and albumins according to their solubility in certain aqueous solvents. Biochemically, oilseed globulins are generally considered storage proteins while albumins are believed to be metabolic (catalytic) proteins. 

From amino acid compositions, evaluations o7" the nutritional potentials of cucurbit meals and globulins can be calculated according to FA0/WH0 (54). The A E ratios, which are the amounts of each essential amino acid relative to the total amount of essential amino acids, are shown in Table II. These data indicate that, like most other oilseeds, cucurbit seeds are deficient in lysine and sulfur-containing amino acids. However, sulfur-containing amino acids are considerably high in CitrullI us colocynthis (egusi, ancestral watermelon) seed protein and exceed the suggested level in FA0/WH0 reference protein (55). 

Recent nutritional evaluations of cucurbit seeds have accentuated the currently popular Buffalo gourd ( . foetidissima) and are shown in Table III. PER (protein efficiency ratio) values of full-fat and natural and autoclaved fat-free meals fed to weanling... 

Because composition and nutritional properties of the major food legumes and oilseeds have been reported in numerous technical journals and books (listed above), the section devoted to composition and chemistry highlights lesser-known but potentially important sources of plant protein that have not received the same attention. Some of these food crops have been cultivated for many years so that they are not "new" sources. Such crops as winged bean, sweet potato, tropical seeds, fruits and leaves, yams and cucurbits are potential sources of protein in areas where they are grown. These are discussed in greater detail in the remaining five chapters. 

The seeds of many plants contain fat as the major carbon reserve in some, such as those of castor bean, this is stored in the endosperm tissue surrounding the embryo, while in those of cucurbits and other plants it is stored in the cotyledons. Electron micrographs of the storage tissue show that the cells are almost completely occupied by spherosomes (membrane-bound vesicles of fat) and by protein bodies (e.g.. Vigil, 1970). 

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