Nutritional Evaluation of Buffalo Gourd: Elemental Analysis of S e e d I

MARK LANCASTER, 2 RICHARD STOREY, 2 AND NATHAN W. BOWER 3

Cucurbi ta foetidissima is a native American wild plant with potential as a protein food and oil source. Research has previously been done on the compo- sition of its amino acids and oils and on methods for cultivating it. This paper provides a comprehensive mineral analysis of the seeds and whole gourds and demonstrates that nutritional qualities of the buffalo gourd compare favorably with dry cow-feed. Buffalo gourd seed was also found to contain a trypsin inhib- itor.

The buffalo gourd (Cucurbita foetidissima HBK) is a wild perennial gourd indigenous to the arid and semiarid regions of the southwestern United States and northern Mexico. The gourd has a combination of attributes that make it particularly suited as an oilseed and feed crop. These include its perennial nature, its ability to grow on poor lands with little rainfall, its production of abundant fruit rich in oil and protein, and the fact that the plant can be harvested mechan- ically (Bemis et al., 1979). Furthermore, every part of the plant has potential as a feed crop, since the vines can be used as a fodder, while the roots are high in starch (Berry et al, 1976). The plant has a long life expectancy with one report of a plant producing oil-rich fruit for over 40 yr, and, while the vines are frost sensitive, the roots have been known to survive air temperatures as low as -25~ in established stands (Bemis et al., 1979). Early work (Shahani et al., 1951) in- dicated the plant was relatively immune to the common cucurbit pests, but more recently Rosemeyer et al. (1982) have found that in cultivated fields the gourd is susceptible to a number of common plant pathogens.

As a wild plant, the buffalo gourd shows promise for improvement through genetic and environmental manipulation. Large variations in plants per acre, fruit per plant, seed per fruit, and even nutrients per seed support this idea (Bemis et al., 1979). Buffalo gourd is sexually dimorphic with both monoecious and gynoe- cious sex types occurring in natural stands (Bemis et al., 1978; Dossey et al., 1981). The plant can also reproduce asexually via root propagation.

One method of cultivation proposed by Bemis et al. (1979) involves establishing a field by direct seeding, followed by a vine harvest at the end of the first season. Vines of the plant could be used as sheep fodder when dried and supplemented with molasses and phosphorus (Cossack et al., 1979). The next season, asexual propagation from the roots could increase the plant stand by a factor of 5-10. A second vine harvest would yield oil- and protein-rich seeds and more vines for fodder. During the next dormant season some of the roots, which have a high starch content, would be dug to thin the field. The remaining roots would develop

1 Received 2 August 1982; accepted 30 November 1982. 2 Biology Dept., Colorado College. 3 Author to whom correspondence should be addressed. Chemistry Department, Colorado CoLlege,

Colorado Springs, CO 80903.

Economic Botany, 37(3), 1983, pp. 306-309 1983, by the New York Botanical Garden, Bronx, NY 10458

1983] LANCASTER ET AL.: BUFFALO GOURD 307

the following season and would proliferate the vines and fruit. In this manner all parts of the plant would be utilized.

In feeding studies with poultry, Daghir et al. (1980) found the seed meal to be toxic, though the results were not reproducible. Bitter cucurbitacins, which are toxic to mammals (David and Vallance, 1955), are present to some degree in the roots, stems, leaves, and fruit, though they are apparently absent in the seeds, which have been used successfully in feeding studies with mice (Bemis et al., 1979).

Interest in the buffalo gourd initially centered primarily in its potential as an oilseed crop. Vasconcellos et al. (1980) characterized this and developed a pro- cess (Vasconcellos and Berry, 1982) for producing an edible oil of high quality. Koury et al. (1982) found that the oil contains no toxic substances interfering with growth rate studies on chicks and that it is relatively high in linoleic and low in linolenic acids. Scheerens et al. (1978) report some variability in the fatty acid composition of the oil, suggesting the potential for agronomic improvement through selection and breeding.

The seed meal has also been investigated as a protein source (Jacks et al., 1972). Using whole egg as a standard, buffalo gourd seeds were found to have a protein score of 28, an essential amino acid index of 62, a protein efficiency ratio of 1.5, and a net protein retention value of 2.2 (Bemis et al., 1979). These values indicate that defatted buffalo gourd seed meal compares favorably with soybean and cottonseed meal. Weight gain experiments with mice confirmed that buffalo gourd was lacking in lysine, methionine, threonine, and valine as compared with control diets of whole egg. When fed a diet of buffalo gourd seeds supplemented with the above amino acids, the mice showed weight gains equal to those on the whole egg diet (Bemis et al., 1979).

Work is also being conducted on the presence of antinutritional components, such as proteolytic enzyme inhibitors and hemagglutenins, that would inhibit the use of buffalo gourd seeds as a food source for monogastric animals (Bemis et al., 1979; Henderson and Berry, 1981).

Despite the work on the oil and amino acids found in buffalo gourd, almost no research has been reported on its mineral content. Therefore, this study was undertaken to evaluate the nutritionally important elements found in the seeds and in the pulp and shell of buffalo gourds growing in Colorado. The results are compared with a dry cow-ration (Siegmund, 1973) in order to evaluate the gourds as a potential feed source.

MATERIALS AND METHODS

Mature buffalo gourd (Cucurbita foetidissima HBK, Mansfield 1014, COCO) fruits were collected from natural stands in southern El Paso County, Colorado, during the fall of 1981. The seeds to be analyzed for mineral content were sep- arated from the shells and pulp after drying the opened gourds in an oven over- night at 110~ This was accomplished by manually separating the seeds from the dried pulp with sieves. This procedure circumvented the difficulties encountered when trying to remove the seeds from the tough, fibrous pericarp of the fresh fruits. After drying, both the separated seeds and the whole gourds were readily digested with hot nitric acid. Flame atomic absorption was used to determine all

308 ECONOMIC BOTANY [VOL. 37

TABLE 1. NUTRIENT CONTENT OF VARIOUS FEED RATIONS. a

Separated gourd seeds Whole gourd h Dry cow ration ~

Protein (g) 316 269 85 (N • 6.25)

Oil (g) 260 180 - - Fiber (g) 310 210 150 Ash (g) 54 86

Sodium (g) 0.4 1.4 1 Potass ium (g) 10 45 7 Calcium (g) 2.6 4.2 3.4 Magnes ium (g) 2.0 1.9 0.8 Iron (mg) 150 100 100 Manganese (rag) 17 15 20 Zinc (nag) 81 41 40 Copper (mg) 7.7 4.7 10 Cobalt (mg) <0.1 <0.1 0.1 M o l y b d e n u m <2 <2 <6

Chlorine (g) 6.5 5.2 1,5 Sulfur (g) 0.7 0.6 2.0 Phosphorus (g) 7.0 3.6 2.6

a Amount per kg of dry matter feed. Consists of 31% seed by weight.

c Siegmund, 1973.

metals except sodium and potassium, which were determined by flame emission using a Varian 275B. Phosphorus, nitrogen, chloride, and sulfur were determined by colorimetry, Kjehldahl titration, argentiometric titration, and barium sulfate turbidimetry, respectively. Oil and crude fiber were measured by standard AOAC methods (Horwitz, 1980). Trypsin inhibitor activity was assayed as described by Samac and Storey, 1981.

OBSERVATIONS AND DISCUSSION

The results of the elemental analysis of the buffalo gourd fruits are presented in Table 1. The dried seeds were found to contain 31.6% protein, 26% oil, 31.0% fiber, and 5.4% ash by weight, in good agreement with values of 31.7% protein, 23% oil, 26.5% fiber, and 4.8% ash reported by Shahani et al. (1951). With this high protein content, it can be seen (Table 1) that even the whole gourds with their 26.9% protein appear to be a potential food source, though the presence of toxins may limit this use. Bemis et al. (1979) suggest supplementation of buffalo gourd seed meal may be necessary prior to use as an animal feed because of the relatively high fiber and ash content and the reported amino acid deficiencies.

Although the element concentrations could be analyzed to an instrumental reproducibility of less than 5%, sampling reproducibility was limited to about 25%, since the amount of seeds per gourd varied as well as the mineral content. Except for the high magnesium and potassium and low sulfur concentrations, the element nutrients in the whole gourd are generally satisfactory as a feed source when compared to dry cow-rations. The low levels of sulfur are in keeping with the generally low levels of the sulfur-containing amino acids reported previously (Bemis et al., 1979). The low levels of phosphorus reported by Cossack et al.

1983] LANCASTER ET AL.: BUFFALO GOURD 309

(1979) in the stems and leaves do not appear in the seeds, though the rest of the gourd has a low value of 0.2% phosphorus, in agreement with Cossack's value of 0.17%.

Buffalo gourd seeds contained trypsin-inhibitor activity, but only about 30% on a fresh weight basis of that found in jojoba seeds and about 7% of that found in raw soybean (Samac and Storey, 1981). These values are in agreement with those recently reported by Henderson and Berry (1981). The relatively small amount of activity was heat labile and if the seeds are processed properly it should present no nutritional problems in feed containing buffalo gourd seed meal.

The primary purpose for cultivating buffalo gourd has been to harvest the oil in the seed. When the seeds are mechanically separated from the fruit and the oil is extracted for commercial purposes, the residual seed meal retains most of the gourd's protein and nutrient elements. Subsequent use of this meal as a livestock feed would substantially increase the agronomic potential of the plant and make it more appealing to entrepreneurs.

LITERATURE CITED

Bemis, W. P., J. W. Berry, C. W. Weber, and T. W. Witaker. 1978. The buffalo gourd: a new potential horticultural crop. Hortscience 13: 235-240. , - - , and C. W. Weber. 1979. The buffalo gourd: A potential arid land crop. In New Agricultural Crops, Gary Ritchie, ed, p. 65-87. AAAS Selected Symposium Series 38. West- view Press, Boulder, CO.

Berry, J. W., C. W. Weber, M. L. Dreher, and W. P. Bemis. 1976. Chemical composition of buffalo gourd, a potential food source. J. Food Sci. 41: 465--466.

Cossack, Z., L. B. Waymack, C. W. Weber, and J. C. Scheerens. 1979. Nutritional availability of buffalo gourd (Cucurbita foetidissima). Amer. Soc. Anim. Sci. Proc., W.S. 30: 156--158.

Daghir, N. J., H. K. Mahmoud, and A. E1-Zein. 1980. Buffalo gourd (Cucurbitafoetidissirna) meal: Nutritive value and detoxification. Nutr. Rep. Int. 21: 837-848.

David, A., and D. K. Vallance. 1955. Bitter principles of Cucurbitaceae. J. Pharm. Pharmacol. 7: 295-296.

Dossey, B. F., W. P. Bemis, and J. C. Scheerens. 1981. Genetic control of gynoecy in the buffalo gourd. J. Heredity 72: 355-356.

Henderson, C. W., and J. W. Berry. 1981. Antinutritional factors in xerophytic and commercial cucurbits. XII Int. Congr. of Nutr., San Diego, CA.

Horwitz, W., ed. 1980. Official Methods of Analysis, 13th ed. Association Official Analytical Chem- ists, Washingston, DC.

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Khoury, N. N., S. Dagher, and W. Sawaya. 1982. Chemical and physical characteristics, fatty acid composition and toxicity of buffalo gourd oil. J. Food. Technol. 17: 19-26.

Rosemeyer, M. E., B. H. Wells, and A. Zeid. 1982. Diseases of the buffalo gourd, Cucurbita foetidissima, in Arizona. Phytopathology 72: 955.

Samac, D., and R. Storey. 1981. Proteolytic and trypsin inhibitor activity in germinating jojoba seeds (Simmondsia chinensis). PI. Physiol. 68: 1339-1344.

Scheerens, J. C., W. P. Bemis, M. L. Dreher, and J. W. Berry. 1978. Phenotypic variation in fruit and seed characteristics of buffalo gourd. J. Amer. Oil Chem. Soc. 55: 523-525.

Shahani, H. S., F. G. DoUear, and K. S. Markley. 1951. The buffalo gourd, a potential oilseed crop of the southwestern drylands. J. Amer. Oil Chem. Soc. 28: 90-95.

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