Abstract
Assessment of the phytochemical, proximate, vitamins and mineral composition of S. gilo L was undertaken using standard methods. The phytochemical screening revealed that the plant contained tannins, saponins, phenols, cyanogenic glycosides, alkaloids and flavonoids, The results showed that S. gilo L had alkaloid content of 6±2.23%, flavonoid 19.5±0.02%, saponin 5±0.3%), tannin 1±0.24%, phenol 1.8±0.02%, and cyanogenic glycosides 4.7±0.21%. The proximate analysis showed a moisture content of (6±1.41%),ash (14.8±0.02%) crude fiber (29.33±0.02%), lipid (37.61±0.01%), protein (0.18±0 .02%) and carbohydrate (13.03±0.01%). S. gilo L. also showed high level of vitamins including vitamin B1 (1.2±0.16µg), vitamin B2 (10.71±0.16 µg) vitamin C (264±2.15 mg/g), vitamin B3 (7.33±0.02 µg). It also showed trace amounts of vitamin E (0.52±0.02 µg), high mineral contents of potassium (4150±2.14mg/g) and sodium (270±1.41 mg/g), and trace amounts of other elements including lead (0.04±0.01 mg/g) and cadmium (0.025±0.002 mg/g). The result show that S. gilo L is endowed with appreciable amounts of bioactive substances and nutritive components which justifies its wide use in ethnomedicine and as stew condiment as well as being used food.
CHAPTER ONE
INTRODUCTION
• Background information
African eggplants are wild relatives of the common eggplant (Solanum melongena) (Schippers, 2000). They belong to the Solanum genus, and comprises of cultivated species such as the Solanum macrocarpon L., Solanum aethiopicum L. and Solanum anguivi; which are grown mostly in Africa for their fruits and leaves. Both S. aethiopicum L. and S. macrocarporn L. are native to Africa (Daunay, Lester, & Ano, 2001) whereas common eggplant (S. melongena) is of Asian origin (Meyer et al., 2012).
The S. aethiopicum L. is one of the five most important vegetables of tropical Africa, together with tomato, onion, pepper and okra (Lim, 2015; Maundu, Achigan-Dako, & Morimoto, 2009; Schippers, 2000). In Kenya, Tanzania, Uganda and Rwanda, it is considered a common vegetable consumed for nutrition, besides medicinal and economic purposes (Lester & Daunay, 2003; Weinberger & Msuya, 2004). S. aethiopicum L. is a phenotypically diverse species which is subdivided into four cultivar groups (Gilo, Kumba, Shum, and Aculeatum) (Lester, 1986). Gilo is the commonly cultivated group in Africa and together with Kumba; they are used for their fruits while Kumba and Shum are used for their leaves. Aculeatum group is utilized as ornamental as well as a rootstock (Daunay, 2008; Lester & Daunay, 2003; Schippers, 2000).
Nutritionally, reports have indicated that African eggplant as a vegetable, is recommended for tackling malnutrition problem in Africa, especially among women of child bearing age and children under 5 years old (Chadha & Oluoch, 2003). In addition and of interest, African eggplants are a rich source of phytochemicals including the anthocyanin as well as the phenolic acids (Daunay, 2008). These contribute to the fruit organoleptic properties by imparting a bitter taste and interfering with other molecules during the cooking process (Daunay et al., 2001a). Furthermore, these phytochemical components are high in antioxidant and antiradical activities that are responsible for reducing the risk of radical-mediated pathogenesis such as carcinogenesis, atherosclerosis, diabetes, Alzheimer, cataracts and age-related functional decline (Atoui, et al., 2005; Stommel & Whitaker, 2003; Zhang & Hamauzu, 2004). Medical research studies have proven that African eggplant possess anti-inflammatory property, hypo- lipidemic effect, antispasmodic activity and anti-ulcerogenic property (Anosike et al., 2012; Chioma et al., 2011; Hassan et al., 2006; Odetola et al., 2004). These reports support the various traditional uses of the plant in different parts of Africa where either the roots, leaves, flowers or the fruits are used to treat various conditions such as colic, high blood pressure, uterine complaints, throat infections, gastric ailments, getting rid of hookworms, as a sedative and a laxative. (Lim, 2015). Economically, African eggplant offers gainful employment among the rural households and its cultivation is not limited to any age or sex. Women, in particular, use the eggplants as an additional source of income. (Anuebunwa, 2007).
Recently, there has been increase in consumer awareness towards bioactive components and their potential health benefits, leading to preference of foods which contain more functional bioactive compounds. Consequently, food processors are increasingly focusing on food products with higher bioactive compounds and their maximal retention during processing to meet the market trend (Nambi, et al., 2016). With regard to this, African eggplant has increased in its demand and production. On the flip side, increased production is accompanied by increase in postharvest losses due to their perishable nature or garden egg as it is commonly called in many parts of Nigeria where they are used for hospitality in place of kola nuts and as stew condiments with other Solanum species in traditional medicine as antioxidants and laxatives [1,2,3]. The species is Solanacaea and the plant genus solanum which have over 1000 species worldwide of which about 25 species are known in Nigeria including those domesticated and wild ones with their leaves, fruits or both used as vegetables or in traditional medicine [4]. Solanum gilo is cultivated in Africa including Nigeria [5] as an annual crop and is usually called “afufa” in Igbo, where there are many other Nigerian and other African species and varieties [6].
The garden egg species are commonly consumed almost on daily basis by both rural and urban families. The eggplants form part of the traditional Sub-Saharan African culture. The fruits, said to represent blessings and fruits, are offered as a token of goodwill during visits, marriages and other social events.
There are wide variations existing within and between the African eggplant species including variation in characters like diameter of corolla, petiole length, leaf blade width, plant branching, fruit shape, color [7].
Solanum gilo is grown in areas of high rainfall. The fruits are around with the top and bottom flattened out and have grooved portions with a length of 5-6cm and a width of 6-7cm. It possesses very tiny seeds and its stalk is curved or erect. [8].This species of garden egg have bitter taste and is cultivated in the same way with other species. The fruit turn red or orange in colour when ripened.
The use of the African egg plant in indigenous medicine range from weight reduction to treatment of several ailments including constipation, weight loss, obesity, diabetes, glaucoma, rheumatic disease and swollen joint pains [9]. These pharmacological properties have been attributed to the presence of certain chemical substances in the plants such as crude fiber, phenols, ascorbic acid, and alkaloids [10].
In this study, nutritive and phytochemical, vitamin and mineral analyses were carried out on an indigenous egg plant S. gilo L. because of its nutritive and medicinal benefits.
• Problem statement
There is limited literature on the nutritional, economical and value addition of African eggplant, despite its inclusion in the top five list of important vegetables in tropical Africa (Ismail et al., 2004; Jiménez et al., 2009). There have been reports showing that African eggplants are rich in phytochemicals which possess antioxidant and antiradical activities responsible for reducing the risk of radical-mediated pathogenesis such as cancer, atherosclerosis, diabetes, Alzheimer, cataracts and age-related functional decline (Atoui et al., 2005; Lim, 2015; Stommel & Whitaker, 2003; Zhang & Hamauzu, 2004). The increasing interest in the health and nutritional benefits associated with phytochemicals has led to increased demand of foods that are rich in bioactive compounds (Nambi et al., 2016).
In Kenya, cultivation and consumption of African eggplants is popular in the coastal region and is slowly spreading to other parts. African eggplants are rich in phytochemicals and are high yielding crops with about 10kg per plant (National Research Council, 2006). However, increased production is accompanied by post- harvest losses (PHLs) estimated to be up to 25% due to poor post-harvest handling practices (Chadha, 2006; Hornal, Timpo & Guillaume, 2007). Perishable commodities such as African eggplants have a limited shelf life in fresh state and normally require cold chain systems during handling, transport and distribution to prevent PHLs and maintain quality. Unfortunately, these facilities are inadequate or poorly established in developing countries such as Kenya. Furthermore, perishable commodities are sensitive to chilling injury (Yahia, Barry-Ryan, & Dris, 2004). Exposure to prolonged periods of chilling stress lead to irreversible symptoms such as surface lesions and pitting, internal discoloration, water-soaking of the tissue, off- flavour, failure to ripen, and decay (Yahia, et al., 2004).
Drying of African eggplants can be used to minimize PHLs and improve their shelf life stability. However, drying can plausibly cause damage to the inherent nutrients and bioactive compounds through food degradation (oxidation, discoloration, shrinkage, or loss of tissue) and change the food‟s nutritional value (Chang et al., 2006; Mayor & Sereno, 2004; Swanson & McCurdy, 2009) depending on the drying method and treatment conditions. A study on the drying characteristics of African eggplants is critical in conceptualizing the drying process and setting dryer controls. The choice of the drying method and optimization of the drying process is important for bioactive compounds retention (Akdaş & Başlar, 2015). Therefore, drying requires optimization of a number of procedures including the time of harvest, the slice sizes, the temperature time combinations and the packaging and its effects on nutrition (Doymaz, 2009; Zaro, et al., 2015).
• Justification
Recently, there has been increase in consumer awareness towards bioactive components and their potential health benefits, leading to preference for foods which contain more functional bioactive compounds. Consequently, food processors are increasingly focusing on food products with higher bioactive compounds and their maximal retention during processing to meet the market trend (Nambi et al., 2016). Postharvest losses (PHLs) reduction is a quick impact intervention for enhancing food security (GIZ, 2013a). The FAO and World Bank, approximated that up to 47% of USD 940 billion needed to eradicate hunger in Sub-Saharan Africa (SSA) by 2050 will be required in the postharvest sector (FAO–World Bank, 2010). Reducing food losses therefore offers an important pathway of availing food, alleviating poverty, and improving nutrition. Many global food security initiatives and organizations such as the World Bank‟s Global Agriculture and Food Security Program have positioned themselves to tackle PHLs. In Sub-Saharan Africa, PHLs reduction is also prioritized in the agricultural and food security strategic plans of national governments. Ever since the first World Food Conference of 1974, various approaches and technologies have been applied and promoted to counter PHLs (Affognon et al., 2015). In line with this, the development of adequate postharvest treatments for fresh produce, and their optimum use are of great necessity and economic importance. Adequate postharvest treatments should reduce losses, and preserve perishable foods to meet consumer demands for constant availability and good quality throughout the year.
Drying technology is simple, safe and easy to learn. Drying reduces the water activity thus preventing microbial activity from thriving. In addition, drying slows down or inactivates the enzymes action, reduces the weight and volume of commodities thus reducing the packaging and transportation costs. (Clark, 2009; Yahia et al., 2004; Swanson & McCurdy, 2009). Enormous losses in terms of money and labour besides steep rise in prices of commodities during the off season are also reduced (Sagar & Suresh, 2010). PHLs in African eggplant could be minimized through drying since the shelf life is stabilized. As a result, African eggplants potentiality as an income source and availability during off seasons and drought periods might be improved.
Application of drying technology provides a suitable alternative to cold chains systems which are absent or inadequate in Kenya. Optimization of the drying process is critical for a quality dried product to be achieved and also for cost effectiveness as it shortens drying time and minimizes damage to the product (Sagar & Suresh, 2010). The community and industrialists may benefit by using the findings of this study to add value to the African eggplants. In addition, the reports from this study are an addition into the body of knowledge acting as a point of reference for future researchers who venture into related projects.
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