Eggplant, brinjal or aubergine (Solanum melongena L.) is together with tomato among the most widely
known edible fruits of the Solanaceae family (Daunay, 2008). Eggplants are thought to be derived from
the wild African species, Solanum incanum. The scarlet eggplant (Solanum aethiopicum L.) and the
gboma eggplant (Solanum macrocarpon L.), grown and consumed in Africa and represent an important
source of genetic variation (Daunay et al., 2001b).
Eggplants were already domesticated in Southeast Asia, particularly in Northeast India and southeast
China more than 2000 years ago (Sekara et al., 2007). Historical, morphological, and molecular evidence suggests that the Indochinese region is the primary center of diversity of S. melongena (MuñozFalcón et al., 2009). The species was then introduced in Europe through Spain from where it spread to
New World (Prohens et al., 2005).
With an implanted surface of 1.8 million of ha, eggplant world production is 46.6 million Ton
(FAOSTAT, 2014). China and India are the major growing countries with 60% and 25% of the total
volume respectively, followed by Iran (2.7%), Egypt (2.5%), Turkey (1.8%), Indonesia (1.1%), and Japan
(0.7%). Spain, Italy, and Greece concentrate most eggplant production in Europe. Eggplant world commerce has shown a growing trend. In 2012 exports reached 440,000 Ton, the main contributors being
Spain, Jordan, Mexico, the Netherlands and Syria, Germany, France, and the United Kingdom. U.S.
production is not sufficient to cover the domestic demands and the country together with Russia, Canada,
Iraq, and Italy accounts for 75% of global imports (FAOSTAT, 2014).
Morphology, Varietal Groups, and Crop Requirements
Eggplants have a strong and well-developed root system. The stem is 0.5–2 m tall and may often be spiny.
Leaves are large (10–20 cm), lanceolate, and coarsely lobulated (Figure 21.1). Most varieties bloom in
three to five flowers bunches. Flowers are large, white, or purple-white and have a five-lobed corolla and
large anthers (Figure 21.2). Their long style difficult self-pollination, but the plant is mainly autogamous
(Daunay et al., 2001a).
Some early cultivars having ovoid fruit are thought to be responsible for the name “egg-plant.” The
berries require a period of 25–40 days to reach harvest maturity. In fully developed fruit, the calyx
remains as accessory tissue. In contrast to other fruits in which growth and ripening are clearly delimited,
- eggplant expansion continues until advanced ripening stages (Figure 21.3). Remarkable variability in
- fruit color (white to green, yellow, purple, black, or striped), shape (ovoid, rounded, elongate, or pyriform), and size (15–1500 g) is found among cultivars (Nothmann, 1986). The seeds are white or yellow
- and may keep their viability for 4–6 years (Sekara et al., 2007). The edible portion includes the pulp
- placental tissue and seeds and in some preparations the peel.
- Different classifications have used to group eggplant varieties. Bailey’s (1947) identified three varietal
- groups: var. esculentum which comprises the commercially common forms with intermediate size, var.
- serpentinum including varieties with very long fruit, and var. depressum grouping genotypes with small
- fruit. Other attributes used for classification purposes are the pericarp color, the presence of spines in
- the calyx, and the fruit length covered by the calyx. Purple eggplants are more popular in Western markets. From a commercial perspective, Cantwell and Suslow (2013) subdivided the most common varietal
- groups marketed in the United States:
- • American: Oval or globular in shape, firm, with dark purple skin, and green calyx.
- • Japanese: Oblong, thin, light or dark purple colored skin and very perishable fruit.
- • Chinese: Oblong, thin and light purple colored varieties.
- • White: Small fruit, oval or globular in shape, with thin and light skin.
- • Mini-Japanese: small, spherical striated, or purple.
- Eggplant is a warm-season crop that requires 60–85 days for cycle completion. The plant needs a 10–12 h
- photoperiod and performs best at relatively high temperatures (the optimum being around 23°C–26°C)
- (Sekara et al., 2007). Thus, the crop is grown during the summer season. Eggplants are very sensitive to
- cool weather and do not perform well when exposed to low temperature. In cool seasons flowering, fertility, and fruit set are severely affected (Nothmann and Koller, 1975). At 10°C–12°C growth is arrested
- and flowering and fructification are markedly compromised.
- Well-drained sandy loam, loam, or clay loam soils having a good supply of organic matter and pH of
- 6.0–6.5 are best for growing eggplants. Plant spacing varies from 45 to 60 cm between plants, and 60
- to 100 cm between rows depending on the cultivar and cultural practices. Since yields and fruit quality
- are reduced in 2 year plants, eggplants are normally managed as a single season crop (Nothmann, 1986).
- Though the level of bioactive components may depend on the cultivar (Nothmann, 1986; Zaro, 2014),
- fruit proximate composition remains fairly constant across genotypes. Water is by far the most abundant
- components with more than 90% of the total fruit weight (Table 21.1). Fiber is particularly abundant (3%)
- compared to other foods and even to other vegetable sources. Proteins and lipids are present at very low levels. The major sugars are glucose and fructose which range between 0.8% and 1.5%. Sucrose and maltose
- are present but in low concentration (Rodriguez et al., 1999). Organic acids found at relatively low levels
- (ca. 0.1%) and are more abundant in the outer pulp (near to the peel) as opposed to sugars which are more
- prevalent in the inner flesh (Zaro et al., 2014a). As for other vegetables, eggplant has low energy density (25
- and 19 cal per 100 g of raw and cooked fruit, respectively). The fruit has moderate levels of most vitamins
- and minerals but are relatively rich in potassium. The berries are low in sodium and have no cholesterol.
- Similarly to other Solanaceous species, eggplants were at once believed to be poisonous due to the
- presence of steroidal glycoalkaloids. Recent studies have indicated that low intakes of some glycoalkaloids may exert some potentially beneficial effects such as the inhibition of some types of cancerous
- cells and the formation of complexes with cholesterol (Mennella et al., 2010; Sánchez-Mata et al., 2010).
- Solasonine and solamargine, the main eggplants alkaloids are normally present at nontoxic concentrations (Mennella et al., 2010), but may confer bitter taste (Sánchez-Mata et al., 2010).
- In the last years, eggplants have received higher interest due to their high levels of bioactive compounds. In a study evaluating the antioxidant capacity of different fresh vegetables, eggplants ranked
- within the top 10 (Cao et al., 1996). Eggplant extracts inhibited inflammation and radical-mediated
- pathogenesis, carcinogenesis, and atherosclerosis (Han et al., 2003; Matsubara et al., 2005). High eggplant intake exerted hepatoprotective (Akanitapichat et al., 2010) and hypolipidemic effects also reduced
- plasma glucose levels in rats (Sudheesh et al., 1997; Derivi et al., 2002).
- Eggplant berries are not particularly rich in ascorbic acid (400–700 mg kg DW−1) (Zaro, 2014) or
- carotenoids (40–100 mg kg DW−1) (El-Qudah, 2009). The health-promoting effects have been associated
- with phenolic compounds which are particularly abundant (0.5%–1.5% DW) both in the peel and flesh.
- Hydroxycinnamic acid derivatives, and mainly free chlorogenic acid (ChA, 5-O-caffeoylquinic acid) is
- the major phenolic in eggplant (Whitaker and Stommel, 2003; Concellón et al., 2012). ChA is high at
- early developmental stages (20 g kg DW−1) and decreases by 50% at commercial harvest maturity (80%
- full size) (Zaro et al., 2014b). Other forms (3-O-, 4-O-, and 5-O-cis isomers) of caffeoylquinic acid, 3,5-
- and 4,5-dicaffeoylquinic acid, amide, and acetyl ester conjugates have been identified (Whitaker and
- Stommel, 2003; Prohens et al., 2007). ChA shows an uneven distribution within the fruit, being more
- abundant in the inner pulp than in the outer flesh (near to the peel) where is mainly associated with fruit
- fibers and vasculature (Figure 21.4) (Zaro et al., 2014a).