Template:Chapter 9.6

9.6 - Cucurbit seeds as a source of protein and nutrients

Kirsten Radcliffe, University of Guelph, Canada

Suggested citation for this chapter.

Radcliffe,K (2022) Cucurbit seeds as a source of protein and nutrients, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org

Introduction

Today, approximately half of the world’s population lives on less than $2USD per day (WHO, NMH, & NHD, 2012). One of the most pressing challenges faced by this demographic is malnutrition. According to the WHO et al., a strong correlation exists between instances of underweight children and absolute poverty (2002). Mothers and children tend to be most affected by under nutrition. This malnutrition tends to occur when a lack of protein or energy is compounded with a micronutrient deficiency such as iodine, iron, or vitamin A (Haddad et al., 2014). Undernutrition is a multifaceted issue, encompassing a combination of inadequate diet and frequent infection, leading to further deficiencies in micronutrients (WHO et al., 2012). WHO et al. estimates that 27% (168 million) of children under five years old and 27-51% of women of reproductive age are underweight (2002). These statistics represent those who are categorized as severely underweight. However, the fatal risks associated with under nutrition are not limited to this demographic; even mild under nutrition can put an individual at an increased risk of dying from ensuing illness or infection (Haddad et al., 2014). According to the WHO et al., approximately 50-70% of the burden of diarrhoea, measles, malaria, and lower respiratory infections in childhood is attributed to under nutrition (2002).

As depicted in Table 1 below, protein related deficiencies prevail worldwide especially in the case of children under the age of five, contributing to conditions such as stunting and wasting. Lack of dietary protein tends to be a consequence of food insecurity due to factors such as crop failure from drought, disease, or pests (Guilbert, 2003). Iron deficiencies are also a prominent issue worldwide, effecting primarily women of reproductive age and children (Haddad et al., 2014). Iron is vital to numerous bodily processes such as carrying oxygen from the lungs to other tissues via red blood cells (UNICEF, WHO, & The World Bank, 2012). Lack of Iodine is another predominant nutritional issue worldwide effecting 28% of the population (Black et al., 2013). Iodine is essential in regulating thyroid hormones, insufficient iodine can result in difficulty swallowing or breathing (Haddad et al., 2014; World Health Organization & Food and Agriculture Organization of The United Nations, 2004).

Potential of Cucurbitaceae Seeds

The Cucurbitaceae family represents a promising solution to reducing undernourishment worldwide. Egusi (Colocynthis citrullus L.) and pepita (Cucurbita pepo) are two underutilized species within this family whose seeds represent an excellent source of protein and micronutrients. Although seeds of legumes and pulses are typically looked towards as sources of high quality protein, the seeds of the cucurbit family are often overlooked. As illustrated in Tables 2 and 3, both egusi and pepita significantly contribute to fulfilling the daily nutritional requirements, especially in case of protein, fat, iron, and zinc.

Colocynthis citrullus L. (Egusi) produces bitter flavoured melon-type fruits similar to a cantaloupe (Akobundu et al., 1982). Egusi is a tendril climbing annual which is known to be tolerant of drought, humid environments, and depleted soils (Okoli, 1984). Grown widely in West Africa, this crop occupies an important role in the diet and culture of many ethnic groups (Okoli, 1984). Due to widespread popularity in various regions throughout Africa, Egusi seeds are relatively inexpensive and readily available making them excellent for diffusion to other countries (Achu et al., 2005). The seeds contain 24.8% protein (60% in defatted flour) and are rich in the essential amino acids: arginine, tryptophan, and methionine (Akobundu et al., 1982). Amino acids are the building block of protein, incorporating all nine essential amino acids is vital to maintaining a complete diet. In the case of Egusi seed, this would mean combining a food high in lysine such as soybeans (or other legume grain) into meals (Achu et al., 2005). The addition of lysine increases the availability of protein from the seeds (Akobundu et al., 1982). Lack of protein in a diet can be extremely problematic, leading to conditions such as wasting or stunting (WHO et al., 2002). Egusi seeds hold significant potential in providing a high protein food source and improving food security.

Defatted Egusi seeds can be ground up into flour, increasing available protein, calcium, thiamin, and niacin (Akobundu et al., 1982). The increased calcium availability in the flour has been found to be especially beneficial in regions where milk consumption is low (Akobundu et al., 1982). Utilizing Egusi in the form of flour not only has added nutritional benefits but could also increase adoption rates since flour is a popular cooking commodity in various cultures. In another method of preparation the seeds are soaked, boiled, blackened with charcoal. Then the seeds are wrapped in banana leaves for fermentation, producing a food seasoner known as "ogiri-isi", which can be added to soups, providing flavour and thickening properties (Okoli, 1984). Alternatively, the seeds can be roasted like peanuts and consumed as a snack type food (Okoli, 1984). All of these additional processing methods enrich nutritional value by increasing protein and mineral availability and extend shelf life (Stevenson et al., 2007).

Cucurbita pepo contains eight groups of cultivars commonly grown for consumption, which includes pumpkin, scallop, acorn, crookneck, straightneck, vegetable marrow, cocozelle, and zucchini (Paris, 1989). These cultivated forms are domesticates of wild forms originating from North-eastern Mexico and Texas (Paris, 1989). Pepita seeds typically refer to roasted pumpkin seeds, traditionally consumed in Latin America (Lira & Caballero, 2002). These seeds are high in oil, protein, tocopherols, and carbohydrates (Achu et al. 2005). The oil is composed primarily of polyunsaturated fatty acids, providing a high source of energy (Noor Raihana et al., 2015). Pumpkin seeds are also rich in tocopherols, also known as vitamin E, which is a fat-soluble antioxidant important for protection against toxins and eye disorders such as cataracts (World Health Organization & Food and Agriculture Organization of The United Nations, 2004). The meat of the pumpkin can also be consumed, providing a substantial dietary source of both vitamin C and A (Noor Raihana, Marikkar, Amin, & Shuhaimi, 2015). Similarly to egusi seeds, the high protein and unsaturated oils make pepita a valuable dietary protein source and high value cooking oil. Pumpkin seed oil colour tends to vary from dark green to brown and can be stored for longer periods of time since it is highly unsaturated (Stevenson et al., 2007).

Challenges

Although egusi seeds hold promising potential as a dietary protein source, they are high in phytic acid, reducing the availability of minerals (Enujiugha & Ayodele-Oni 2003). However, high phytate levels can be reduced through further processing such as heating or soaking (Enujiugha & Ayodele-Oni 2003). Another aspect of egusi nutritional content which should be taken into consideration is that it is relatively low in histidine, an essential amino acid for infants (Akobundu et al., 1982). Flour and oils are utilized worldwide in various culinary practices, however, the oil and flour processed from egusi and pumpkin seeds may vary in taste or colour reducing the likelihood of adoption. In order for pumpkin seeds to be consumed they must first be de-shelled; there are machines available to perform this task in larger quantities but they tend to be quite expensive. De-shelling by hand can be extremely time consuming which may deter adoption. An additional challenge is that egusi is relatively susceptible to root-knot nematodes which pose a substantial challenge to maintaining yields. The growing region may influence the crop losses associated with this pest, as will access to extension services. In order for the potential of cucurbit seeds as a protein source to be utilized, there needs to be more research and funding. Unfortunately, research funding tends to be predominantly Western led, who may not

Picture Based Lesson to Train Farmers

Click on the image to access a higher resolution image as well as lessons adapted for different geographic regions.

Source: MN Raizada and L Smith (2016) A Picture Book of Best Practices for Subsistence Farmers. eBook, University of Guelph Sustainable Agriculture Kit (SAK) Project, June 2016, Guelph, Canada.

receive the same degree of benefits from the expansion of this protein source.

Further Reading

 http://www.wikihow.com/Shell-Pumpkin-Seeds - Provides steps and associated graphics detailing how to de-shell pumpkin seeds

 Pumpkin Extension Manuals: http://extension.psu.edu/business/ag-alternatives/horticulture/melons-and-pumpkins/pumpkin-production http://www.infonet-biovision.org/PlantHealth/Crops/Pumpkin

 Egusi Extension Manuals: https://www.nap.edu/read/11763/chapter/10#170

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