Composition and botanical properties of watermelon rind

Botanical properties:

The composition of Citrallus lanatus (water melon) is 93% water, hence giving the name “water” melon.  The “melon” aspect is the product of the fruit being big, round and a soft, pulpy texture. The scientific name of water melon comes from both the Greek and Latin sources. The Citrullus part is derived from a Greek word “citrus” which refers to the fruit. The lanatus part is from Latin language and means to be fuzzy, referring to the small hairs on the plant’s stems and leaves.

Watermelon is believed to have been originated in southern Africa as it grows in the wild region and reaches largest diversity of forms there. It has been grown for over 4,000 years in Africa. Spanish brought Citrullus lanatus to America and it quickly became the very popular one. Citrullus lanatus is a prostrate or annual climbing plant with many herbaceous, firm and sturdy stems up to 3m in length. The young parts are heavily woolly with yellow to brownish hair, meanwhile the older parts are colorless. The leaves are herbaceous but stiff, being dull on both sides; 60-200mm long and 40-150m thick, but usually 3-lobed or doubly lobed again’ the central lobe is much higher. The leaf stalks are very hairy and have a length of up to 150mm. The tendrils are very robust and normally split into the upper portion. On the same (monoecious) plant, male and female flowers occur with the flower stalk up to 400mm long up to 150mm. Subglobose is its wild form, indehiscent and having diameter of up to 200mm, while fruit stalk is up to 50mm in length.

Typically the fruit is globose to oblong or ellipsoid, often ovoid, 5–70 cm long and weighing 0.1–3.0 kg (0.1–2.5 kg in egusi melon, 1.5–3.0 kg in watermelon), the seeds are obovate to elliptical, rounded, 0.5–1.5 cm x 0.5–1 cm, smooth, yellow to brown or black, hardly white.

Nutrient composition:

The weight by weight composition of Citrullus lanatus consists of around 6% sugar and 92% fat. As with a lot of other fruit, it is a source of vitamin C. The composition of dried egusi seed per 100 g, without shell is; Water 5.1 g, energy 2340 kJ (557 kcal), protein 28.3 g, fat 47.4 g, carbohydrate 15.3 g, calcium 54 mg, phosphorus 755 mg, iron 7.3 mg, thiamin 0.19 mg, riboflavin 0.15 mg, niacin 3.55 mg and folate 58 μg. The seed is an excellent source of nutrition, and does not contain any hydrocyanic acid, which makes it suitable for animal feed. Linoleic, oleic, palmitic and stearic acid glycosides are present in seed oil. The flesh of fruits produces bitter cucurbitacins.

Watermelon composition per 100 g edible portion (50–70 percent of ripe fruit) includes: water  0.4g, carbohydrate 7.2 g, calcium 8 mg, phosphorous 9 mg, iron 0.17 mg, thiamine 0.08 mg, riboflavin 0.02 mg, niacin 0.2 mg, folate 2 mg and ascorbic acid 9.6 mg.

Watermelon is a rich natural source of lycopene, a highly important carotenoid due to its antioxidant ability and associated health benefits. Plants of cucurbitaceae contain bioactive compounds, such as cucurbitacin, triterpenes, sterols and alkaloids.

Every part of watermelon fruit has nutritional value, including the rind and the seeds. The most common way to consume watermelon is pink or yellow flesh consumption, eaten raw, the way it was grown. Other common types, however, include pickles of watermelon rind, deep fried watermelon, watermelon cake and watermelon lemonade.

Dietary fibers (soluble, insoluble, total):

The key form of fiber present in watermelon rind is insoluble fiber (50.32 g/100 g), which has been associated with many health benefits including a decreased risk of cardiovascular disease and weight gain, diabetes and other cancers. Among fruits, watermelon has been traditionally considered as good source of fibers (>0.5g/100g edible portion) with remarkable contents in both soluble and insoluble fibers.

Flavonoids:

Flavonoids have antifungal, antioxidant and antibacterial properties, therefore the availability of flavonoid in the samples recommends that their use offer protection against the diseases which is related to free radicals, fungal and bacterial activities. Phytonutrients analysis exposed the presence of flavonoids. Phytonutrients is a natural bioactive compound from plants which have many generals benefits to human health.

The total flavonoids content of saccharomyces cerevisiae was significantly increase in fermented watermelon as compared to unfermented watermelon rind. the best described property of almost every group of flavonoids is that it acts as antioxidants. The most powerful flavonoids are flavones which protect the body against ROS. Consumption of flavonoids can be used in the managing of coronary heart disease. Watermelon rind was chosen as the chief ingredient for production of natural food preservation. We choose watermelon rind because it contained flavonoids and anthocyanins. Flavonoids have high antioxidant. Antioxidant activities have been widely studied in different foodstuffs. Antioxidant activities of foodstuff increases with the presence of high concentration of total flavonoids.

Phytate:

Phytate are anti nutrient which are naturally occurring compound found in all plants that reduce the ability of body to absorb essential nutrients. Phytate is an anti-nutritional, On the bioavailability of essential dietary minerals negative phytate have many. negative effects. Phytate is mostly considered antinutritional factor, because it is implicated with the impaired absorption of minerals. Phytates is a natural antioxidant and the presence of phytate in the samples is indicative of antioxidant benefit following their consumption.

Phytic acid is the storage form of phosphate and inositol generally in seeds and grains to minerals such as iron, zinc, copper, calcium, and magnesium, and inhibit their absorption by the small intestine. In the body Phytates bind to calcium and iron. Phytate cannot digest by human body, hence it is not a nutritional source of inositol or phosphate. In the body Phytates bind to iron and calcium and could prevent their absorption into the body causing deficiencies.  Phytic acid is harmful for those who have deficiencies of zinc, iron. as an antioxidants phytic acid have positive dietetic impact which prevent carcinogenesis for this purpose determining the phytic acid content of foods is essential. The phytate levels had a range of 0.3g/100 g dry matter. The alkaloid, saponin, phytates and oxalate content in each sample were determined by the colorimetric method for phytate and alkaloid the absorbance of each sample was measured at 420 nm.in watermelon rind phytate is present in very lowest amount.

Cyanide:

The cyanide content in the food samples was determined by the alkaline picrate method. There was no cyanide is present in the watermelon rind while the amount in the seed (0.79±0.01 mg/100 g) was comparably much lower than the value (30.24±0.02 mg/100 g) in sweet potatoes leaves. The absence of cyanide in the rind is nutritionally significant in interpretation of the general cyanide toxicity which is formed when acids react on metal cyanides.

The levels of hydrogen cyanides ranged from 26.96 ± 0.01 to 121.02 ± 0.02mg/ 100g. The lowest level was obtained in pomegranate rinds and the highest in watermelon rind. Within a few minutes High dose of hydrogen cyanide can cause death, while lesser dosages may result to stiffness of the throat, chest, palpitation and muscle weakness. The result obtained falls within the threshold value (below 350 mg/ 100g) reported as safety limit. Severe cyanide toxicity at low doses between 0.5 and 3.5 mgkg-1 body can cause headache, tightness in throat, and muscle weakness. Symptoms of acute cyanide poisoning include; rapid respiration, drop in blood pressure, rapid pulse, headache, dizziness, vomiting, diarrhea, mental confusion, stupor, cyanosis, twitching and convulsions. In order to prevent cyanide toxicity, processing procedures such as peeling, grating, crushing, grinding, soaking, fermenting and drying have been used for centuries to reduce potential toxicity of cyanogenic plants before consumption.