Nutritional Composition of Staple Food Bananas of Three Cultivars in India

Banana (Musa spp.) is an important ingredient of several dishes and its nutritional and other biochemical composition at different stages is yet to be scientifically studied. In the present study the most popularly cultivated species of Nendran, Nijali poovan and Robusta banana in Southern India are selected. Variations in the nutritional and biochemical compositions associated with ripened and unripened stages of banana fruits were studied. Proximate composition, mineral and phytochemical compositions of ripened and unripened banana flours were analyzed and the total soluble sugars in unripened banana range from 1.70 to 2.15 mg/100g of the samples and that of ripened banana range from 37.5 to 43.8 mg/100g of the samples. Mineral compositions show that they are rich sources of calcium, phosphorus and iron. In addition to this they are rich sources of antioxidant potential phytochemicals such as polyphenols, flavanoids, vitamin C and lesser in quantity of anti nutritional factors such as phytates and oxalates. The current study revealed the variations of biochemical compositions of three varieties in unripened and ripened stages. This will be useful for the exploitation of these crops to obtain and formulate the value added products.


Introduction
Banana is one of the most popular desert fruit, in terms of per capita consumption as well as the most widely traded fruit in the world. India is the largest producer of banana accounting for 17.8% of world share followed by Barzil [1].
Fruits and vegetables are rich sources of various health beneficial phytochem-The development of new product is a strategic area at the food industry. Consumers demand foods mainly of two reasons, one in deal with the traditional nutritional aspects of foods, whereas the second feature is that the additional health benefits accepted from its regular ingestion and such kinds of food products are called nutraceutical foods [9]. India is the largest producer of banana, its share in the world trade is merging at present. Bulk of banana produced in the country is utilized in domestic market as fresh fruit but for a few processed products like chips. There is immense potential for processing banana into several value added products like dehydrated ripe banana jam, jelly, fruit bar, wine, vinegar, puree, baby food and pickle which can fetch profit both in the domestic as well as in the foreign market [10].
Banana fruits are rich source of nutrients and their biochemical composition varies with growth stage and maturity [11]. The study of nutritional status of the banana fruits will be useful for exploitation of the crop to obtain value added products. Therefore, the present work was undertaken to study the nutritional and biochemical compositions of three different varieties of ripened and unripened bananas such as Nendran, Nijali poovan and Robusta. The study emphasizes the nutritional and biochemical compositions of these varieties and their changes upon ripening.

Preparation of Sample
The ripe and unripe varieties of Musa AAA Spp. (Robusta), Musa AAB Spp.

Chemical Analysis
The moisture, ash and protein content in the samples were determined accord-American Journal of Plant Sciences ing to methods described in AOAC [12]. Total ash content in the sample was determined by ignition in muffle furnace at 550˚C for 6 h. The total protein in the sample was determined by using Biuret method [13]. The crude fat was determined using the Soxhlet extractor and the solvents used were chloroform and methanol according to Bligh and Dyer methods [14]. Crude fiber was estimated in the samples by following acid and alkali treatment methods according to AOAC [15]. Total soluble sugars were estimated by the methods of Dubois et al. [16]. Reducing sugars were estimated by method of Somogyi [17] and the amount of non reducing sugars was calculated as the difference between total soluble sugars and reducing sugars. Fructose content of the sample was estimated by the method of Ashwell [18].
The pH of the sample was determined by methods given by Berwal et al. [19].
10 g of sample was weighed and it was macerated with 100 mL of deionized water. It was thoroughly mixed and the mixture was allowed to stand for 30 minutes. The supernatant was collected by centrifugation at 7863 g for 15 min using refrigerated centrifuge and the supernatant was decanted and determined the pH. Vitamin C of samples was estimated by the method of Robinson and Scotz [20].
Phytic acid was determined by the method of Davis and Reid [21]. Finely  Oxalic acid was estimated by the method of Raghuramulu et al. [24]. 5 g finely ground samples were mixed with 100 mL of 2N hydrochloric acid and the mixtures were shaken on a rotary shaker 150 rpm for 2 hrs. The mixtures were boiled for 15 minutes, at 100˚C and then cooled to room temperature (37˚C). To 25 mL of the filtrates, 5 mL of phosphoric tungstate reagent was added, stirred well and kept overnight at room temperature (37˚C). The following day, the filtrates were centrifuged at 7863 g for 15 min and filtered. To 20 mL of the filtrates, 2 or 3 drops of methyl red and neutralized with ammonia, 5 mL of calcium chloride buffer were added and stirred well. The mixtures were allowed to stand overnight. Next day, the mixtures were filtered through Whatman no. 40 paper. To the precipitates, 5 mL of 2 N sulphuric acid was added and heated at 80˚C and titrated against 0.01 N potassium permanganate solutions (standardized with 0.01 N oxalic acid). The oxalic acid content was expressed as mg/100g of the sample. Mineral compositions such as calcium, phosphorus and iron were estimated from acid digested samples. Reagents-diacid mixture: Nitric acid and perchloric acid were mixed in the ratio of 5:1. Finely ground samples (1 g) were taken in conical flask containing 25 mL diacid mixture and kept overnight. The following day, the samples were digested by heating till a clear white precipitate settled down at the bottom. The crystals were dissolved by the addition of deionized water. The contents were filtered through Whatman no.42 paper. Final volume was made up to 50 mL with deionized water and used for the determination of individual minerals.
Calcium in the digested solution was estimated by the method of Raghuramulu et al. [24]. An aliquot (1 mL) of digested solution was pipette out into centrifuge tubes. A drop of methyl red indicator was added to the tubes till the solution turned light pink followed by the addition of few drops of liquid ammonia till the solution turned light yellow. A drop of glacial acetic acid was added to give a salmon pink color indicating the correct pH for the precipitation of the calcium. The contents were mixed well followed by the addition of 1 mL of ammonium oxalate solution and kept overnight. The following day, the tubes were centrifuged at 7863 g for 15 min. The supernatants were discarded by inverting the tubes carefully on a clean filter paper. To the precipitates, 4 mL of liquid ammonia was added and centrifuged at 7863 g for 15 min. The supernatants were discarded and the process was repeated 2 to 3 times. To the pellets, 10 mL of 1 N sulphuric acid was added and kept in boiling water bath (100˚C) till the contents started simmering and titrated against 0.01 N potassium permanganate (Standardized with 0.01 N oxalic acid). The end point was a definite pink color which persisted for at least 1 minute. The calcium content was expressed as mg/100g of the sample.
The iron content was estimated by the method of Raghuramulu et al. [24]. To

Statistical Analysis
Experiments were carried out in three replicates and presented as means ± standard deviation of three replicates. One way ANOVA was carried out to examine whether the difference in the chemical components present in the different samples were significant or not. SPSS software (version 17) was used for the analysis.

Dehydration Details of Banana
Three different varieties of unripened and ripened bananas were dried separately in an electric oven at 60˚C for 12 hrs. It was observed that 100 gm of fresh ripened banana subjecting to oven drying yielded Rn (37.5 g), Rp (30.22 g) and Rr (24.5 g) respectively (Table 1). However, unripened banana varieties yielded Un (45.14 g), Up (39.78 g) and Ur (30.6 g) respectively. It was observed that, the unripened oven dried bananas weighed more than the ripened oven dried banana varieties. This could be due to higher content of proto-pectin in unripened fruit which gets converted to pectin as the fruit ripened [25].

Proximate Composition
The result of the proximate composition of the three different varieties of unripened and ripened bananas are given in Table 2.
The moisture content was ranged from 39.40% to 60.06% in unripened and 66.23% to 75.25% in ripened banana respectively. The bananas generally contain 60% -68.6% of moisture as they ripen; it gradually increases from 68.6% -78.1% [26].  [32] reported that ash content of banana fruits shows variations, which may be due to the differential absorption capacity of minerals at different stages of fruit development.

Carbohydrate Composition
The crude fiber content was highest in unriped fruits (2 -4 g/100g) compared to ripened fruits (1 -2.42 g/100g). The food value of crude fiber is greater, which helps to regulate certain physiological functions. The highest crude fiber content was observed in unriped nendran banana (4 g/100g). The crude fiber composition of unriped banana was observed to be high and it later dropped at the ripened stage [37]. The low fiber level of banana can be used for fortifying the weaning food. However, those fruits with high fiber content are desirable in adult diet, which are known to aid digestion, prevent constipation, help to the excretion of wastes and toxins from the body and also prevent colon cancer [38] [39].
The total soluble sugar content shows highest in ripened stage (37 -43.8 g/100g) compared to unripened banana (1.7 -2 g/100g). Increase of total soluble sugars while ripening is an important trait of hydrolysis of starch into soluble sugars such as glucose, sucrose and fructose [29] [40] [41]. The fructose content in the unripened banana flour was ranging from 0.4 g to 0.5 g/100g, whereas in the ripened samples ranging from 9 g to 11.95 g/100g of the samples. Reducing and non reducing content was highest in ripened fruits than unripened banana fruits (Table 2). In terms of the total carbohydrate contents of banana was high in the ripened stage, may be due to the high level of sugar, starch and dietary fibers [42].

Mineral Composition
Banana contains rich sources of mineral nutrients and it could serve as mineral element supplement in diet for both humans and animals [26] [40]. Mineral nutrients such as Calcium, phosphorus and Iron content of the ripened and unripened banana samples are given in Table 3. respectively. In comparison Ur and Rr, contains same amount of iron (1 mg/100g) whereas, the unripened and ripened Nendran and Njali poovan varieties showed slight increase in their iron content during their maturation stage.
The gradually increasing in the mineral contents of banana fruits during ripening stages is already reported [43].

Phytochemical Composition of Banana
Polyphenols are the biggest group of phytochemicals found in plant based foods and the structure of natural polyphenols varies from simple molecules to highly polymerized compounds. Majority of polyphenols existed as glycosides with different sugar units and acylated sugars at different positions of the polyphenol skeletons [44]. Banana peel represents about 40% of total weight of the fresh fruit [45]. The total amount of phenolic compounds in banana peel has been reported from 0.9 -3 g/100g dry weight [46] [47]. The phytochemical composition of unripe and ripe banana variety mg/100g is presented in mg/100g respectively. The present study showed an increase in polyphenol content during ripening. Newilah et al. [48] was studied in the increasing levels of  respectively. In all the analyzed samples the flavanoids content shows that decreasing order from unripened banana to ripened fruit, except in the Nendran banana sample (Un-112mg and Rn-115mg). Fathemeh et al. [50] reported that the higher level of flavanoids in unripe banana than ripe banana fruit. The variation in the flavanoids content among different plant materials might be attributed to factors such as natural chemical composition, maturity at harvest, soil state and conditions of post harvest storage [51].
Vitamin C is an anti-oxidant and it acts as a good scavenger of several reactive oxygen species [52]. The value of vitamin C of samples ranged from 0.5 -0.73 mg/100g in unripened banana and that of ripened fruits ranging from 0.54 to 0.72 mg/100g respectively. Fresh green banana is reported as a good source of vitamin C, but almost 65% of it is lost when made into flour [53].
Phyticacid is a natural plant inositolhexaphosphate commonly found in seeds and represents the principle form of stored phosphate [54]. Phytic acid forms complexes with proteins (Protein-Phytate complex) and chelates essential dietary minerals such as Fe, Zn, Cu and Mg thus decrease their utilization [55]. The phytate content of analyzed unripened banana samples was ranging from 0.037 to 0.08 mg/100g, whereas 0.031 to 0.317 mg/100g in ripened banana fruits. Adeniji et al. [56] reported the low level of phytate content of musa hybrids between 1.2 × 10 −5 to 11.0 × 10 −5 .

Conclusion
The present study reveals that the nutritional compositions are affected by vari-