Comparative study of chemical composition and evaluation of the In-Vitro antioxidant capacity of unripe and ripe banana species (Musa Sapientum) biowastes

The effort of developing countries in addressing zero hunger (Goal 2) with good health and well-being (Goal 3) of Sustainable Development Agenda requires a multidisciplinary analytical approach to waste materials capable of decomposing through aerobic and anaerobic conditions. Hence a research on ripe and unripe banana peels as potential sources of nutrients, essential minerals and antioxidants was carried out using standard analytical techniques. The study revealed that the percentage moisture of the unripe and ripe banana peels ranged from 4.60 – 17.8; crude protein 1.94 – 2.73; fat 1.76 – 3.25; ash content 11.3 – 14.7; crude fi bre 14.2 – 15.5; and carbohydrates 48.4 – 52.7. Mineral content showed signifi cantly high levels of Na, K, Ca, Zn, Fe in unripe peels while that of ripe exhibited higher levels of Mn and P. Na/K for both ripe and unripe banana peels is less than 1 while Ca/P ranged from 1.63 2.64. The antioxidant capacity using 2, 2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) assay ranged from 3.75 13.6 mg TE/g and total phenolic content in unripe and ripe banana peels ranged from 8.42 15.8 mg GAE/g with higher value in unripe peels. The results indicate that the peels can be utilized as sources of fi bre, carbohydrate and essential minerals in fortifi cation of animal feeds. Research Article Comparative study of chemical composition and evaluation of the In-Vitro antioxidant capacity of unripe and ripe banana species (Musa Sapientum) biowastes Ibiyinka Ogunlade1*, Akinwumi Oluwafemi Akinmade2, Adebayo O Ogunlade3 and Olugbenga Kayode Popoola1 1Department of Chemistry, Ekiti State University, PMB 5363, Ado-Ekiti, Ekiti State, Nigeria 2Department of Industrial Chemistry, Ekiti State University, PMB 5363, Ado-Ekiti, Ekiti State, Nigeria 3Center for Healthful Behavior Change, Department of Population Health, School of Medicine, New York University, New York, USA Received: 29 November, 2020 Accepted: 12 February, 2021 Published: 15 February, 2021 *Corresponding author: Ibiyinka Ogunlade, Department of Chemistry, Ekiti State University, PMB 5363, Ado-Ekiti, Ekiti State, Nigeria, E-mail:


Introduction
Consumption of fruits has a crucial role in human diet and demand for such important food commodities has increased very signifi cantly as a result of growing world population and the changing dietary habits (Russel & Gould, 1999). Fruits and vegetables are the most utilized commodities among all horticultural crops [1]. They are eaten raw, minimally processed with some undergoing natural processing such as ripening. High production and growth, and lack of proper handling methods and storage infrastructure, have led to the generation of huge biowastes which are usually discarded. The United Nations Food and Agricultural Organization (FAO) has estimated that at least one third of the food produced globally (estimated as 1.3 billion metric tons) is lost and wasted every year [2] and biowastes are the highest among all types of foods, reaching up to 60 % [3]. Banana is one of the most important crops of the tropical plants. It belongs to the family Musaceae and the genus Musa sapientum. It is a climacteric fruit, consumed mostly when the fruit is ripe; ripe and unripe https://www.peertechz.com/journals/international-journal-of-agricultural-science-and-food-technology Citation: Ogunlade

Total equivalent antioxidant capacity determination
The radical scavenging potential of the banana peels extract was determined using 2,2-diphenyl-1-picryl-hydrazylhydrate (DPPH) assay as previously described [18]. 50 mg of each sample was extracted with 20 mL of ethanol and fi ltered.
Working solution of DPPH having absorbance of the range 800 -1000 at 525 nm was prepared fresh. 0.1 mL of the extract was pipette into a test tube and 9.9 mL of the DPPH solution added and incubated at room temperature for 30 mins (enough time to reach a stable value). This was then transferred into a cuvette and the absorbance was taken at 525 nm. 6-Hydroxyl-2,5,7,8-tetramethylchroman-2-carboxylic acid (trolox) was used as a standard reference to convert the inhibition capacity of each sample to the trolox equivalent antioxidant capacity (TEAC). Standard trolox solution in ethanol were prepared at a concentration of range between 0 -600 μg/mL. 0.1 mL of each trolox solution was added to 9.9 mL of DPPH radical solution (0 -24 μM trolox in radical solution). The absorbance was read after 30 mins of incubation at room temperature using Jenway 6705 UV/VIS Spectrophotometer. Results were expressed as mmol trolox equivalents per gram (mM TE/g) extract.

Determination of the total phenolic content
The total phenolic content of the plant extracts was determined using the established Folin Ciocalteu method [19]. A volume of 25 mL of each extract was incubated in a clear 96-well fl at bottom plate for 5 min with 125 mL freshly prepared 0.2 N. Folin Ciocalteu's phenol reagent (100 mL 7.5 % sodium carbonate) was added and incubated for 2 hours.
The absorbance at 760 nm was measured and the total phenols calculated using the standard gallic acid in 10 % ethanol.
Results were expressed as milligram gallic acid equivalents per gram (mg GAE/g) extract.
banana are also processed into snacks and juice. Banana is very perishable and subject to fast deterioration after harvesting.
For this reason, high quantities of wastes are being generated prior to consumption and also high quantities of fruits are lost during their commercialization due to poor post harvesting handling. Banana biowastes include the pseudostem, leaves, infl orescence, fruit stalk, rhizome and peels. Documented literature highlighted the valorization of the wastes including banana peels, which constitute a measurable percent of the banana fruit, proven to be a rich source of crude fi bre, carbohydrates, crude protein and essential minerals [4]. This shows its potential of serving as basal materials or components of animal feed. Furthermore, banana peels are used as adsorbent in water purifi cation Chaparadza & Hossenlopp [5] like other natural materials such as pecan shells, rubber seed coat, jute fi ber, olive stones, pine wood, Indian rosewood sawdust and clay minerals that are usually applied for this purpose [6][7][8][9][10][11][12][13]. It is also used for ethanol production [14] and also in composting) [15].

Proximate composition analysis
Proximate compositions of the banana peels samples were determined for moisture, fat and ash, in triplicates. The protein content was determined by a semi micro Kjeldahl method while the crude fi ber content was determined using standard methods as described by AOAC, 1986 [16]. The carbohydrate content was determined by difference.

Mineral composition analysis
The concentration of the mineral content of the samples was carried out in accordance to the existing protocol of Pearson [17] with little modifi cation. The procedure involved

Results and discussion
The proximate composition of unripe and ripe peels of local M. Sapientum varieties  [20,21]. The peels demonstrated a high percent of ash from 11.3 ± 0.16 -14.7 ± 0.04. Higher percent was observed in unripe and ripe cavendish banana peel (13.5 ± 0.07 and 14.7 ± 0.04 respectively) and that could suggest that peels of cavendish banana as rich source of minerals. It was also observed that the calculated metabolizable energy, crude Desirable fl avour, quality and texture are usually attained in fruits by ripening processes. Ripening process, in turn is usually accompanied by a change in the chemical composition of fruits.
In Table 2, we have the differences in the mean proximate composition of ripe and unripe peels of M. sapientum. Table   2 shows the progressive increase or decrease in the chemical composition of banana peels due to ripening. From the result,  ripening seems to be a depleting factor. It was observed that the moisture and protein content of the peels increased due to ripening. The result shows that ripe peels exhibits a low shelf life of peels and this suggests that utilization of banana peels should be encouraged before ripening takes place or perhaps efforts to preserve the ripe peels need to be engaged. The ash, crude fi bre, carbohydrates, fatty acids and metabolizable energy content also decreases as ripening takes place. The result shows a suitability of unripe banana peels as animal feeds and food supplements compared to ripe peels.

Mineral composition of ripe and unripe peels of M. Sapientum varieties
The result of mineral content (Table 3) shows the presence of high concentration of potassium (K) in the peels. The concentration (mg/100g) ranged within 4565 ± 5 and 4870.0 ±20.0. The peels appreciable high potassium content indicates its potential to regulation of body fl uids and maintains normal blood pressure. Soetan, et al. [22] stressed the importance of calcium as an important constituent of bones and a component actively involved in the regulation of nerve and muscle functions. The study revealed that the calcium content of the peels ranged from 279.0 ± 1.0 -360.0 ± 32.0, with the highest concentration found in unripe red banana peel while ripe baby banana has the lowest concentration. Iron known for oxygen transport is of low concentration in the peels although the low value has also been reported for the fruit [21]. The low concentration suggests that banana peel will be an idyllic source of iron since its excess could result to abnormal functioning of the immune system, cell growth and the heart [23]. Higher Zinc (5.55 ± 0.15 mg/100g ) and potassium level (171.3 ± 0.75 mg/100g) was observed for unripe cavendish banana peels suggest that the peel could play an important role in body defense such as reduction of blood pressure, wound healing and breaking down of carbohydrates. The peel's potential to aid formation of skeletal and cartilage was revealed, as high percentage of manganese was found to be high, ranging from 64.6 ± 0.01 -74.3 ± 0.25 mg/100g. The result also agrees with that reported by Anhwange [24]. The ratio of sodium and potassium in food samples are of great importance as the sodium level often infl uence the increase of blood pressure while potassium aids the maintenance of the blood pressure. It could be suggested that the peels are safe for consumption as the potassium to sodium content is high while the sodium to potassium content is very low. The differences in the mean mineral content of unripe and ripe peels of Musa sapientum presented in Table 4 showed that the sodium and manganese level of the peels increased as ripening takes place in cavandish and red banana which is not so for baby banana peels.
Iron and zinc contents of the peels were observed to decrease randomly in all as a result of ripening. The calcium and calcium to potassium ratio level only increase due to ripening in Cavendish banana peels (44.00(-15.77%) and This could suggest that the potential of the peels as mineral source is highly affected by ripening.
Banana peels have been reported to have a high capacity to scavenge DPPH free radicals and good lipid peroxidation inhibitors [25]. Many studies has also shown that banana peel extract possess a stronger antioxidant activity than pulps [26,27]. The result, as presented in Table 5 shows that the antioxidant properties of banana peels reduced with ripening with values ranging from 3.75 ± 0.16 mg TE/g to 13.64 ± 0.30 mg TE/g. The potential of phenolic compounds as antioxidant is attributed to its ability of inactivating free radicals. The phenolic content of the peel extract ranged from 8.42-15.79mg GAE/g. A comparatively higher value has been reported for rhizomes of various bananas by kandasamy and aradhya [28].
The result presented in Table 5 revealed the presence of higher phenolic content in unripe cavendish banana peels (14.80±0.04) while the lowest percent was found in ripe cavendish banana peels (8.42±0.37). It was also that the phenolic content value varied in the samples due to ripening, with unripe peels having a higher content compared to ripe peels, except in the case of red banana peels [29][30][31].

Conclusion
The study shows that banana peels are reliable source of minerals and bioactive substances in Musa sapientum peels and therefore suggests that the peels possess valuable medicinal potential yet to be exploited. Also, ripening which is often characterized with chemical changes appeared to deplete the chemical composition and the antioxidant properties of the peels. In that case, the study suggest that banana peels, usually discarded as wastes should be utilized as food adjuncts and animal feeds which will boost food security, improve zero hunger and reduce unemployment rate. Furthermore, for the effective utilization of banana peels, unripe banana should be reduced or prevented from ripening as ripening depletes its chemical composition. Not applicable Numbers in parentheses are percentage increase for the mean difference of the mineral content -ve value denotes an enhancement due to ripening +ve value denotes a defl ation due to ripening Mean± Standard deviation of the total phenolic content and the antioxidant capacity of unripe and ripe M. sapientum peels b PAC-Phenol antioxidant coeffi cient calculated as ratio of TEAC(mg TE/g)/ total phenolic content ( mg GAE/g)