Cucurbit Genetics Cooperative Report 23:87-88 (article 30) 2000
An Overview of the Oil Pumpkin
Thomas C. Andres
The Cucurbit Network, 5440 Netherland Ave., D24, Bronx, NY 10471
The use of pumpkin (Cucurbita pepo) seed is not new. The wild gourd-like ancestors of pumpkins contain edible and highly nutritious seeds, and their consumption most likely constitutes the first use of this species. Archaeological evidence shows that soon after the end of the last ice age (over 10,000 years ago), C. pepo was being used and eventually became domesticated in North America. Since the species has multiple uses, selections from the genetically diverse wild populations went in various directions. Seed usage led to selection for larger seed size. This in turn led to larger fruit size with the seeds becoming more readily separable from the pulp. The discovery of wild plants with a mutation for non-bitter flesh led to selections for thicker, higher quality flesh at the expense of seed cavity size and the proportion of seeds per fruit. Pumpkins today are most commonly grown for their flesh with the seeds generally ignored. But there are regions in Mexico where the seeds are still considered the most desirable part of the plant. Landraces in these regions tend to have fruit that are thin-fleshed with proportionally large seed cavities containing seeds that are generally elongated, up to three times longer than wide and thick in cross-section. This seed shape facilitates hand dehulling along the raised margins to remove the indigestible testa. The seeds may be eaten raw or roasted as a snackseed, commonly called "pepitas," or ground into a "pipian" sauce. The testa of the seed varies in thickness and hardness, and thinner testa is tolerated when ground or roasted.
During the sixteenth century, pumpkin was introduced throughout Europe. Central Europe by then already had a well-established oilseed industry, including the pressing of flaxseed (Linum usitatissimum), rapeseed, and other mustard species (Brassica spp.) The high quantity and quality of the oil from pumpkin seeds along with other introduced North American domesticate, the sunflower (Helianthius annus), was soon realized. The oil mills needed to be only slightly modified to take advantage of these new introduced oilseeds. Thus a new use for an ancient domesticate was born.
In the Americas, pumpkin seed was also recognized in folk medicine to be an anthelmintic or vermifuge to expel intestinal worms. When pumpkin seed became popular in Germany, Poland, Austria, Hungary, the Balkans, and Ukraine, a pattern was observed of a low incidence of prostate disorders in this region. This has been attributed to the high consumption of pumpkin seed. A pharmacological study is still needed to substantiate whether there is any unique factor in pumpkin seeds beyond for example a high vitamin content to explain this (Wagner, this volume). The seeds and oil are often advertised as a remedy for urinary problems and benign prostate adenomas and are sometimes old in capsular form mixed with other medicinal herbs. The oil is highly polyunsaturated and rich in protein, and thus of high nutritional value.
Presently in Central and Eastern Europe, particularly in the Austrian province of Styria, a hull-less or so called "naked" seeded strain of pumpkin, sometimes called the Styrian pumpkin, is grown for the production of pumpkin oil. The seedcoat layers are morphologically still present as in regular pumpkin seeds but differ in being membranous rather than having thickened and lignified cell walls. Therefore they require less heat and pressure to extract the more concentrated oil. Furthermore, they may be eaten whole as snackseeds without the need for dehulling.
The origin of this unusual mutation is unclear. There are report at the end of the nineteenth century of this trait in European seeds (Teppner, this volume), although pressing for pumpkin seed oil dates back perhaps a couple of centuries prior to this. In the Americas, there are no reports of oil pumpkins earlier than the first European ones. The first naked seeded cultivar in the United States was 'Lady Godiva', released by the U.S. Department of Agriculture in 1972. It was a selection developed from European landraces. Subsequent cultivars in the U.S. with the naked seeded (or semi naked seeded) trait include 'Eat-It-All', 'Mini-Jack', 'Streaker', 'Trick or Treat', 'Trickster', 'Tricky Jack' and 'Triple Treat'.
Although the mutation is generally believed to have occurred spontaneously in Europe, thin-seeded plants of C. pepo are also found on rare occasion in northern Mexico.
Other countries are beginning to show an interest in the cultivation of oil pumpkin, including Canada, France, China, New Zealand, and Australia. Improvement in the economics of oil pumpkin production and its increased usage will depend on a number of factors including:
- increasing germinability of the easily breakable, rot-prone seeds;
- improving cultural practices;
- improving mechanical methods of harvesting the fruit and seeds;
- optimizing the use of byproducts for animal feed, including: (a) the fruit after the seeds have been removed, and : (b) the pressed seed cakes after the oil has been extracted;
- increasing usage of both seeds and fruit flesh for human consumption;
- developing techniques to cure and extract the oil from the seeds to insure maximum yield and optimal flavor and nutrition;
- improving crop protection and use of locally adapted cultivars through breeding for disease and pest resistance (especially important since pesticides are not generally used);
- genetic improvements to obtain consistent high seed yields by producing a higher number of seeds per hectare and by increasing the oil content per seed, along with improvements in seed size and shape (particularly important for snackseeds), oil composition, color, and taste;
- avoidance of rancidity to improve shelf life of the seed and oil;
- increasing funding for marketing to present more attractive products and educate the consumer on the benefits and uses of pumpkin oil and pumpkin snackseed and promote the environmentally friendly manner in which it is traditionally produced on family-run farms.
All of these factors can help lower the cost and increase the profit of this otherwise high-priced food commodity.
Novel products derived from oil pumpkin seeds, such as the removal of the green endosperm layer of the seed to make a clear straw-colored oil that may be used in frying, need to be explored. The oil from oil pumpkin otherwise comes from pressing the entire seed, which produces a thick dark-colored oil with a low burning point that can not be used in frying. Other under-utilized potential marketable products include seed butter made from the grounded roasted seeds for use as a peanut butter-like sandwich spread and seed flower utilized as a thickener and seasoning. The snackseed may be used as an ingredient whenever other nuts are used, such as in granola or confectionery. Numerous flavors may be tried out on pumpkin snackseeds, such as a wasabi flavoring.
With the high degree of genetic variation in the genome, there is great potential for making breeding improvements in the oil pumpkin. If the recent history of other oilseed crops, such as soybean (Glycine max), sunflower, and specialty flavoring oils, such as walnut oil, provide any lesson, rapid changes in usage may take place.