Nutritional composition and phytochemical content of wild edible tuber (amorphophallus abyssinicus) crop

ABSTRACT There are various neglected and underutilized tuber crops grown in Ethiopia with remarkable nutritional potential, the most prominent being Amorphpohallus abyssinicus. The study aimed to evaluate the nutritional composition, functional property, and phytochemical contents of two cultivars of A. abyssinicus (locally termed as Hambaguyta, and Bagana). Results of the study showed that the two cultivars significantly (p ≤ .05) differ in moisture (11.51%, 9.11%), ash (2.64%, 3.6%) and crude fiber (1.46%, 2.42%) contents for hambaguyta and bagana, respectively. The cultivars were found to possess high carbohydrate (79.37% and 79.15%) and low lipid (0.47%, 0.47%) contents. In terms of mineral composition, calcium was found to be abundant in both cultivars. Bagana tuber has shown higher contents of magnesium (25.19 mg/100 g), Zinc (4.74 mg/100 g), and phosphorus (176.85 mg/100 g) than hambaguyta. However, heavy metals, including lead, arsenic, and mercury were below their detection limits. Phytochemicals: phytate, tannins, oxalate, cyanide, and polyphenols such as total phenol and flavonoid were determined for both cultivars. Good water absorption and low oil absorption capacities were also recorded for the two cultivars. Generally, this study can provide valuable information about these two cultivars as they have ample potential for the application of food and food-related product development.


Introduction
Food and nutritional security are becoming major concerns of many countries in bringing sustainable food systems under climate changes through advanced agriculture embedded with alternative food sources [1] ]. In this regard, root and tuber crops, ranked the second largest group of cultivated species next to cereals, immensely contribute to food security. [2] Consistent with this, Ethiopia is privileged to be a biodiversity hotspot, with highly diversified climate conditions and agro ecosystems suitable for the production of high-quality roots and tubers. [3] The main root and tuber crops grown in Ethiopia include Enset (Eiisete veaniricosum), potato (Solatium tubers), yam (Dioscorea spp.), cassava (Manthatesculanium), anchote (Coccinia abyssinica), and others. [4] farmers with their respective local names "Bagana" and "Hambaguyta." The cultivars were identified by a botanist at the center of Herbarium, 001E/G20, College of Natural and Computational Science, Addis Ababa University, Ethiopia.
About 5 kg of each tuber of the two cultivars were washed to remove debris, peeled carefully using stainless steel knives, rinsed with tap water and then sliced to 5 mm thickness. The slices were oven dried at 60ºC for 48 h. The dried bagana and hambaguyta chips were pulverized into powder for 4 min with an electrical grinder (Nima, model NM8300, Japan) and passed through 250 µm mesh sieve as shown in Figures 2c & 2f. The powder was packed in a separate polyethylene plastic bags and stored at cold storage of 4ºC until analysis.

Proximate compositions
Nutritional compositions of flour samples were determined using the method of Association of Official Analytical Chemists (AOAC). Accordingly, moisture content of the flours was determined using (AOAC, 2012, No-934.06) whereby flour samples were weighted in previously heated, cooled and weighted dish and the contents were heated in the electrical drying oven. Ash content of the flours was determined using (AOAC, 2012, No-923.03) in which the sample was weighted in a previously ignited, cooled, and weighted ashing dish and ignited in a muffle furnace, percentage of ash content was taken by difference, total nitrogen content was determined using an automatic Kjeldahl instrument (Butchi, K-439 Speed Digester, Switzerland) using (AOAC, 2012, No-981.10) where digestion, distillation, and titration were conducted. Finally, percentage of nitrogen was calculated and converted to total protein (% N X 6.25). Crude fat was determined by ether extraction method using soxhlet apparatus (Buchi extraction unit, E-816, Switzerland) (AOAC, 2012, No-920. 39). Crude fiber content was determined through (AOAC, 2012, No-978.10) method. Total carbohydrates (TC) were calculated by difference according to the method of. [15]

Phytochemical compositions
The flour samples were analyzed for phytate, tannin, oxalate, and cyanide contents. The Phytate content was determined according to the method described by. [16] About 0.2 g of dried sample was extracted with 10 mL of 2.4% HCl for 1 h at ambient temperature and centrifuged at 3000 rpm for 30 min. Clear supernatant was used for Phytate estimation; 1mLof Wade reagent (0.03% solution of FeC1 3 .6 H 2 O containing 0.3% sulfosalicylic acid in water) was added to 3 mL of the sample solution and the mixture was centrifuged. Absorbance was measured at 500 nm using UV-VIS spectrophotometer (JascoV-770, Japan). Distilled water with Wade reagent (3 mL of water+1 mL Wade reagent) was used as a control for the assayed sample. Concentration of Phytate was calculated using phytic acid standard curve, and results were expressed as of phytic acids in mg per 100 g dry weight.
phytate mg 100g Tannin contents of both hambaguyta and bagana flour samples were determined according to the method developed by [17] with slight modifications. About,2 g of dried sample was weighed in a screw capped test tube and 10 mL of 1% HCl in methanol was added to each test tube containing the samples. The test tubes were shaken for 24 h at room temperature using mechanical shaker and the tubes were centrifuged for 5 min. 1 mL of the clear supernatant was taken and mixed with 5 mL of vanillin-HCl reagent in another test tube and then the mixture was allowed to stand for 20 min in order to complete the reaction. Then, the absorbance was read at 500 nm using UV-Visible spectrophotometer. Concentration of tannin was calculated using D-Catechin standard curve and the results were expressed as catechin equivalent of tannins in mg per 100 g dry weight. The formula used to determine the tannin content of the samples was: Oxalate content of the two flour samples was determined according to the method of. [18] A sample of about 1g was weighted into separate plastic bottle followed by the addition of 75 mL of 3 mol H 2 SO 4 . The content was thoroughly mixed and allowed for 1 h with constant agitation using a mechanical shaker for extraction. This was then filtered through the Whatman filter paper (42 mm) and 25 mL of the filtrate was titrated with 0.1 N KMnO 4 while hot (80-90ºC) until a purple color was observed at the end point. The titer value was then multiplied by 0.006303 g to express the result as mg/100 g. The obtained oxalate content was expressed as mentioned in AOAC, (2011) which is equivalent with1mL0:1NKMnO 4 ¼ 0:006303goxalate Cyanide content of the two cultivar flours was determined by distillation through the alkaline titration procedure of [19] with little modifications. About 10 g of the flour sample was soaked in the mixture of 200 mL of distilled water and 10 mL of orthophosphoric acid. The mixture was kept for 12 h to release all the bounded cyanide. The mixture was then distilled until 150 mL of the distillate was collected. About 20 mL of 0.02 M sodium hydroxide was added to the distillate and volume of the mixture was marked up to 250 mL in a volumetric flask using distilled water. Then, 4 mL and 1 mL of ammonium solution and potassium iodide, respectively, were added to the 50 ml portions and titrated using 0.02 M silver nitrate. The amount of silver nitrate consumed to the endpoint of the titration was recorded. The endpoint was indicated by a faint permanent turbidity appearance. The cyanide content (mg/100 g) of the sample was calculated as: Where: W represents weight of sample and V represents volume of silver nitrate consumed

Total phenol
Phenol content was determined using the method of. [20] Tuber samples (0.1 g) were refluxed in 80% methanol and evaporated and the volume of the crude extract was made up to 10 mL. An aliquot was prepared with 1 mL extract, 0.5 mL Folin-Ciocalteu's reagent (2:1) and 2 mL of 20% Na 2 CO 3 and the mixture was incubated in a water bath at 90-95°C for 2 min. The absorbance was measured at 650 nm via UV-Vis spectrophotometer (JascoV-770, Japan) and the total phenol content was expressed as gallic acid equivalence (GAE) mgg −1 dw using GA as a standard.

Flavonoid
Crude flavonoid was determined according to the method of. [21] Flour sample of about1g was mixed with 20 mL of 80% aqueous methanol and extracted flavonoids at room temperature by using an ultrasonic bath for 30 min. The solution was filtered through Whatman filter paper No. 42 (12 mm). The filtrate was evaporated on a boiling water bath until a constant weight was obtained. The flavonoids were calculated on dry matter basis.

Mineral contents
Mineral contents of the sample was determined by Microwave Plasma Atomic Emission spectrometer (MP-AES 4210 Agilent, Germany) according to the modified methods of. [22] About 3 g of flour sample was charred by adding drop of HNO 3 . Then, the charred samples were calcinated in a muffle furnace (NaberthermP330, Germany) at 550ºC until a white gray ash is produced. Then, the white ash was dissolved using 10 mL of 6NHCl and dried on a hot plate followed by the addition of 7 mL of 3N HCl and heated again till boiling, filtered through whatman filter paper (42 mm Phosphorus content was determined by ammonium molybdo vanadate colorimetric following the procedure of AOAC (2000) method 965.17. About 1 mL of the digested solution was taken into 100 mL volumetric flask and the volume was filled to the mark with de-ionized water. 5 mL of the solution was taken into test tubes in triplicate to which 0.5 mL ammonium molybdovanadate reagent was added and homogenized. Amino-naphtholesulphonic acid (0.2 mL) was mixed with the sample. The mixture was left to stand for 10 min. The absorbance of yellow color developed for standard, blank, and samples were determined at 460 nm using UV Visible Spectrophotometer.

Heavy metals composition analyses
Trace metal analyses of the flour samples were conducted according to the method used by [23] through dry ashing method with slight modification. About 2.5 g of each sample was weighed into a crucible. The crucible and test sample was placed in muffle furnace at a temperature of 550ºC until ashing. The crucible with ash was put in desiccator to cool. Five (5) mL nitric acid of mass fraction not less than 65% (having a density of approximately ρ (HNO 3 ) = 1400 mg.mL −1) ,) was added, ensuring that all the ash came into contact with the acid and the resultant solution heated on hot plate until the ash dissolved. Ten (10) mL of 0.1 mol.L −1 nitric acid was added and filtered into 50 mL volumetric flask. The resultant solution was topped up to the mark with 0.1 mol.L −1 nitric acid. Blank solution was treated similar as the sample. Atomic Absorption Spectrophotometer (ZEEnit 700P analytic jena, Germany) was used to read the absorbance values (Pb, As and Hg) at a wavelength of (217.0 nm, 193.7 nm and 253.7 nm), respectively.

Vitamins
Vitamin A was determined according to the method of [24] with modification. About 4 g bagana and hambaguyta flour samples were taken and 1 g of pyrogallic acid, 70 mL ethanol, and 30 mL (50%) KOH (for saponification) were added, stirred, and refluxed for 40 min using a water bath at 50 ± 2ºC. Extracts were obtained three times using various ether concentrations (50 mL, 30 mL, and 20 mL). Double-distilled water was used to neutralize the extract, which was dehydrated using anhydrous sodium sulfate. Furthermore, the extract was concentrated to approximately 5 mL by using a Rota vapor evaporator (50 ± 2ºC), diluted to 10 mL by using methanol, filtered using whatman filter paper and finally subjected to HPLC analysis. RP-HPLC analysis was performed with HPLC system (Shimadzu; Japan), including a UV-detector.
The column was made of stainless steel and the solvent was methanol, and UV detection was recorded at 325 nm. Vitamin C was extracted according to a method of [25] with modification. Flour samples, about 5 g of each, were blended and homogenized with an extracting solution containing metaphosphoric acid (0.3 M) and acetic acid (1.4 M). The mixture was placed in a conical flask and agitated at 8,000 rpm for 20 min. The mixture was then filtered through a Whatman filter paper No.4 and samples were extracted in triplicate. The ascorbic acid standard was prepared by dissolving 100 mg of l-ascorbic acid in a metaphosphoric acid (0.3 M)/acetic acid (1.4 M) solution at a final concentration of 0.1 mg/mL. The calibration line was converted to a linear range based on four measured concentration levels (20, 50, 80130ppm). Quantification of ascorbic acid content was performed on Shimadzu HPLC system. Chromatographic separation was achieved on an UV-HPLC detector through isocratic delivery of a mobile phase (A/B 33/67; A: 0.1 M potassium acetate, pH = 4.9, B: acetonitrile: water (50:50)) at a flow rate of 1 mL/min. UV absorbance was recorded at 254 nm at room temperature.

Functional properties
Functional properties of the two cultivars were analyzed for swelling power, solubility index, water absorption capacity, and oil absorption capacity. Swelling power and water solubility index of the flours were determined based on the method of [26] with minor modification. About 0.5 g of the sample and 12.5 mL of distilled water were added to a weighted 15-mL centrifuge tube and mixed thoroughly. Then, the slurry was heated in a thermostatically controlled water bath for 30 min at different temperatures (60-90°C) with frequent mixing at 5 min intervals. The resulting slurries were cooled to room temperature and centrifuged at 3000 rpm for 15 min (Super Vario-N 2016, Germany). To measure solubility, the supernatants were decanted from the sediment into a pre-weighed petri-dish. Aliquots of supernatant were dried in the oven at 105°C till constant weight. The dried supernatant and the sediment were weighed. Finally, the Swelling Power (g/g) and solubility (%) were calculated as follows.
swelling power g g � � ¼ weight of the wet sediment weight of sample taken (5) Water absorption capacity (WAC) and oil absorption capacity (OAC) were determined according to the method of. [27] About 1 g of flour and 10 mL of distilled water/oil were added to the centrifuge tube and mixed thoroughly. Then, the mixed emulsion was heated and stirred in a boiling water bath for 15 min, and then the heated sample was cooled to room temperature and centrifuged in a centrifuge (Super Vario-N 2016, Germany) at 3000rpm for 20 min, the supernatant was poured out. Then WAI and OAC were calculated by the following formula: where W 0 is the weight of the sample, W 1 is the sum of the weight of the sample and the centrifuge tube, and W 2 is the sum of the weight of the sediment and the centrifuge tube where W 0 represents the weight of the flour, V 1 is amount of oil used, and V 2 is the amount of poured supernatant oil after centrifuge

Experimental design and statistical analysis
The experiment was designed in a complete random design with single factor (cultivars) with two levels. All the analyses were conducted in triplicate and the obtained data were statistically analyzed using a one-way analysis of variance (ANOVA), and results were expressed as mean± standard deviation using the Statistical package for social science (SPSS) IBM version 26.0 package. Significance was accepted at P ≤ .05 levels.

Proximate composition
The proximate composition for the two cultivars of A.abyssinicus (bagana and hambaguyta) flour samples are presented in Table 1. The results showed that the two tubers differ (P ≤ .05) significantly in their contents of moisture, ash, and crude fiber, however, has no significant difference shown in their crude fat, crude protein, and total carbohydrate contents. The result also revealed that the moisture content of hambaguyta flour sample (11.51%) and that of bagana (9.11%) were comparable with moisture content values reported for other root and tuber crops' such as dried powder roots of Figli (RaphanusSativus) (11.5-12.9%) as reported by, [28] aerial yam species (5.31-10.94%), [29] Dioscorea. Rotundata (8.08%-12.17%) [30] and Coccinia abyssinica flour (7.1-10.40%) according to the findings of. [31] Food moisture content is an index to determine its water activity and food stability. [32] Foods with high moisture content are more susceptible to microbial contamination while foods with low moisture content can be stored for a long time and suitable for processing in food industries. [33] Results of this study indicated that the moisture content of the flours is lower than the recommended moisture content (12-13%) for excellent storage stability of flours. [34] This implies that bagana and hambaguyta flours are relatively safe for susceptibility of spoilage and can store for further processing. The ash content of hambaguyta and bagana flour samples were 2.64% and 3.6% respectively. These values were comparable with other tubers such as Dioscorea alata (2.50-4.90%), Dioscorea glabra and Dioscorea wallichi wild yam species (2.5-4%), respectively, [35,36] but higher than those values reported for cassava, yam, sweet potato, taro and edible orchids (0.6,1.1, 1.0, 0.9 and 1.2%), respectively, which were reported by [37] and slightly higher than the values reported by [6] for andean roots. The amount of ash in tubers depends on the type of soil from which it was harvested, the moisture content and the maturity of the crop. [35] Textural qualities of certain foods are improved by the formation of starch lipid or starch-surfactant complexes. [38] The tuber's low fat content may make it safe for consumption by people in areas where obesity remains a severe risk to people's health and lives. [39] The result obtained for fat content in the present study was 0.47% for both hambaguyta and bagana flour which were found to be lower than the value of Aduh flour (D.bulbifera) varieties (5.7%) reported by, [40] but higher than the values of potato (0.09%), sweet potato (0.05%), cassava (0.28%), and yam (0.17%) which were reported by. [36] The crude fiber content of hambaguta and bagana flour samples was found to be 1.46% and 2.42%, respectively. These values were lower than the other underutilized tuber crops like water yam (D. alata) which has a value of 3.96% as studied by [41] and slightly higher than potato (2.2%) and cassava (1.8%) which has been reported by. [42] Dietary fiber of food sustains the intestine's healthy microflora and lowers the risk of colon cancer and cardiovascular disease. [36] Increased fiber intake in the diet enhances the large intestine's digestion and absorption process, which helps to prevent constipation and manage blood sugar levels. [35] In all living organisms, protein contributes in the structural and functional activities of cells, as well as the regulation of metabolic activities. [43] A sufficient protein intake in the diet increases the calorific value of the food, which indicates a nutritionally balanced diet. [44] Crude protein contents of hambaguyta and bagana tuber flour were (4.55% and 5.25%), respectively. These values were comparable with the findings of [45] who reported for white yam (5.15%) and water yam (4.88%). In contrast, the values were higher than sweet potato (3.64%), cassava (1.2-1.8%) and D. bulbifera (3.4%) on a dry weight basis as reported by [29,46] Carbohydrate is a key component of the proximate composition of food that gives energy to the body and is essential to the structure and operation of cellular mechanisms. [35] Carbohydrate contents obtained in the study were 79.37% for hambaguyta tuber flour and 79.15% for bagana tuber flour. The results were not showed a markedly difference from those reported by [47] for aerial water yam flour which is (74.18-83.94%) but lower in compared with the carbohydrate contents reported for red cocoyam, 86.69% and sweet potato, 86.90% reported by. [48] Generally, roots and tubers have been reported to be high in carbohydrate and suitably serve as energy staple foods. [29] With this, both cultivars of A.abyssincus have the potential to develop a good source of energy-reach food items.

Phytochemicals composition
Phytochemicals are the naturally occurring chemical compounds produced by regular metabolism that have an impact on the body's nutrient utilization. [1] Phytochemicals reduce the nutritive value of food by lowering the bioavailability of dietary constituents, particularly protein, minerals, and vitamins. [49,50] The phytochemicals including phytate, tannin, oxalate cyanide, total phenol and flavonoid contents of the two cultivars of A.abyssinicus tuber flours were determined and shown in Table 2. Accordingly, the results recorded were significantly (P ≤ .05) different except cyanide. Phytate, which is the storage form of both phosphate and inositol in plant seeds, tubers, and grains is the salt form of phytic acid that mainly exist as mono or divalent cations with K+ Mg 2+ and Ca 2+ ions. [49] Phytate reduces the bioavailability of dietary minerals such zinc, iron, calcium, copper, and magnesium, and could result in mineral deficiency in the body. [51] The phytate content of both hambaguyta and bagana flour samples were found to be 285.33 mg/100 g and 293.31 mg/100 g respectively. These values are much higher than the results obtained for taro (161.13 mg/100 g) and Yam(179.74 mg/100 g) of Ethiopian species by [51] and (58.6-198 mg/100 g) for wild aerial yam (D. alata) species which is reported by [29] and lower than the value reported by [52] for anchote which was (389.30 mg/100 g), roots of cassava (622.2 to 1087.4 mg/100 g). [53] On average, vegetarians consume 2000-2600 mg of phytate per day, but residents of rural areas in developing countries consume 150-1400 mg per day on mixed diets. [54] Tannins are compounds that give foods and beverages their astringent flavor and forms complexes with the food's dietary protein, causing protein precipitation and lowering digestibility and palatability. [29,43] The absorption of minerals like iron and zinc is inhibited by higher tannin content, yet their quantities in foods are known to decrease after cooking. [47,55] Tannin contents of hambaguyta and bagana flour samples were 0.15 mg/100 g and 0.04 mg/100 g, respectively. These results are lower than the values suggested by [29] for aerial yam species with a range of (0.19-0.97 mg/100 g) and similar findings by [21] revealed a value of (0.68-0.72 mg/100 g) for other species of aerial yam tuber flours. Tannin contents of the two cultivar flours are found in lower amount when compared with other root and tuber crops of Ethiopian cultivars such as taro, anchote, and yam, which have values of (32.24 mg/100 g), (173.55 mg/100 g), and (4.54-4.12 mg/100 g), respectively, as reported by. [51,52] The finding indicated that tannin content of A.abyssinicus (bagana and hambaguyta) tuber flour was below the toxicity level (maximum tolerable level 560 mg/100 g) (Food and Nutrition Board, 2005). This leads to a good absorption of minerals and digestibility of the protein found in the food to be made from the two cultivar flours.
Oxalate is found in plants in the form of calcium oxalate, and the insoluble oxalate salts precipitate in the kidney and urinary tract, forming calcium oxalate crystals that cause kidney stones. [49] Oxalic acid forms oxalate salts when it reacts strongly with dietary elements such as calcium, magnesium, sodium, and potassium. [36] Oxalate content of the two cultivar flours was found to be 344.56 mg/100 g for hambaguyta tuber and 315.85 mg/100 g for bagana tuber flour. These results are much higher than oxalate content of other tuber flours such as C.abyssinica (8.26 mg/100 g), [52] and C. esculenta (156.33 mg/100 g) and D.alata (23.33 mg/100 g) as reported by. [51] In contrast, the two cultivars have lower oxalate content than D. bulbifera tubers (550-678.33 mg/100 g) which were resulted in the study of. [46] Oxalate content of bagana and hambaguyta tuber flours analyzed in this study were higher than the recommended level (which should not exceed 50-60 mg per-day) that should exist in individuals as calcium oxalate kidney stones. [56,57] Therefore, traditional processing methods like soaking in salt and boiling before consuming A.abyssinicus can have a positive impact in reducing calcium oxalate, resulting in enhancing the bioavailability of essential dietary minerals of the tuber, as well as reduce the risk of kidney stones occurring on the health of consumers.
Cyanide content of bagana and hambaguyta tuber flours was found to be 6.12 mg/100 g and 6.46 mg/ 100 g respectively. These results are lower than the value stated by [45,52] for different cassava genotypes (8.90-26.9 mg/100 g) and for anchote tuber flour 12.67 mg/100 g, respectively. Plants that accumulate more than 50 to 200 mg/100 g cyanide are considered to be dangerous. [58] The results obtained showed that the two cultivar tuber flours could be considered safe which are below 50 mg/100 g. Besides, smaller amount of cyanides could have several long-term adverse effects on human health. [59] Phenolic content Phenolic compounds have been reported to inhibit the activity of hydrolytic and digestive enzymes and responsible for the bitterness and astringency associated with many foods. [60] The total phenol contents of hambaguyta and bagana flours were 107.63 mg/100 g and 110.70 mg/100 g respectively. These values were lower than phenolic content of D.alata species which were reported by [61] and chicory root which had a value of 865.91 mg GAE/100 g. [62] Good amount of phenols are suggested to be an indicator point for plants that could act as anti-inflammatory, anti-oxidant, anti-clotting, immune enhancer and hormone modulators. [63] Flavonoids Flavonoids are reported to be the most abundant polyphenols in human diets and structurally made of more than one benzene ring. [64] Flavonoids in combination with the dietary minerals such as iron, zinc, and calcium reduces the bioavailability of dietary minerals. [65] Moreover, they are potent watersoluble antioxidants and responsible for ant-microbial, anti-inflammatory and anti-carcinogenic activities. Flavonoid content of hambaguyta and bagana flour was 4.93 mg/100 g and 5.23 mg/100 g. These values were higher than the flavonoid content of white and purple aerial yam flour which had a value of 1.63 mg/100 g and 1.59 mg/100 g respectively. [21] But lower than Xanthosoma tuber which had a value of 11.3 mg/100 g and D.esculenta (12.4 mg/100 g). [66]

Minerals, heavy metals, and vitamin composition
Minerals have significant roles in our body to execute different metabolic functions from building strong bones to transmitting nerve impulses for a healthy and long life. [28,36] The mineral elements detected differed (P ≤ .05) significantly between the two cultivars with the exception of copper, while the heavy metals (Pb, As and Hg) and Vitamin A were not detected in both samples as shown in Table 3.
Calcium is an indispensible mineral in human nutrition for its functioning in blood clotting, muscle contraction, neurological functioning, bone and teeth maintenance, and enzyme metabolic processes. [31,44,60] Calcium content of hambaguyta flour (158.36 mg/100 g) is lower than bagana 215.12 mg/100 g. Calcium content of bagana was higher than the finding of [40] for aduh flour (160.45 mg/100 g) and D. rotundata (8.13 mg/100 g) reported by. [67] In addition, the two cultivars had a comparable high content of calcium than other root and tuber crops such as sweet potato, cassava, and yam with recorded values of (30 mg/100 g,16 mg/100 g and 17 mg/100 g), respectively, according to the finding of, [68] but, lower than 423 to 1190 mg/100 g recorded for aerial yam species as reported by [29] and 280.25 mg/100 g for D. bulbifera has studied by. [46] Generally, the flour from the two cultivars can be used as an alternative source of calcium in food formulation and product development.
Iron is a basic part for formation of blood hemoglobin and helps in transportation of oxygen in the body. The deficiency of iron in the body leads for several complications on humans such as myocardial disease, gastrointestinal infection, and nose bleeding. [44] The iron content of hambaguyta and bagana was found to be 4.12 mg/100 g and 5.67 mg/100 g respectively. The results were higher than 1.34 mg/ 100 g for D.alata and comparable with Amorphophallus paenoiifolius (5.7 mg/100 g) as reported by, [69] but lower than aerial yam (11.1 mg/100 g) and anchote (14.20 mg/100 g) as reported by [29,31] respectively.
Zinc plays a key role in development of brain, bone and helps in metabolic activities of carbohydrate, protein, vitamin A and nucleic acid biosynthesis process. [49] Zinc content of hambaguyta (1.33 mg/100 g) is lower than bagana cultivar (4.74 mg/100 g). These values were lower than the value researched by [35] for D.alata species, which has a value of (10.1-11.1 mg/100 g). The results were slightly higher than yam (0.17-0.36 mg/100 g) as reported by [46] and raw anchote flour (2.20 mg/100 g) according to the findings of. [31] Potassium content in the body increases the iron utilization which is beneficial for diuretics people for controlling hypertension. [1] The concentration of Potassium was 96.35 mg/100 g for hambaguyta and 98.65 mg/100 g for bagana. These values were lower than other root and tuber crops such as aerial yam (387.73-667.53 mg/100 g) and (847 mg/100 g) in similar works documented by [47,70] respectively. The values were also lower than sweet potato and cassava which have recorded values of 337 mg/100 g and 271 mg/100 g, respectively, as reported by. [68] The study indicates that potassium content in the two cultivar tubers cannot meet the recommended daily intake for all age groups (400-5100 mg/day) (Food and Nutrition Board, 2005). Therefore, supplementation of flours with other potassium reach food sources could increase the nutrient uptake of these neglected tubers.
Sodium is an essential nutrient for cellular homeostasis, physiological function, and control of water balance in the body; but, it causes to an elevation of blood pressure when it is found excessive in the body. [35,71] Sodium content found for hambaguyta and bagana flours was 0.4 and 0.73 mg/100 g, respectively. The values were lower than the values for sweet potato (55 mg/100 g), cassava (14 mg/100 g), and yam (9 mg/100 g) as documented by. [68] Sodium content of the two cultivars under study is below the range of the recommended daily allowance (RDA) for all age groups (120-1500 mg/day) (Food and Nutrition Board, 2005), indicating that supplementation from other sodium sources is required. Presently, the food industry is struggling to produce low sodium foods for better health, [28] and in this context, the two cultivars of A.abyssinicus can be alternative potential food resources. World health organization has recommended that the ratio of sodium to potassium (Na: K) should be < 1 for healthy foods (WHO, 2003). Accordingly, the ratios of sodium to potassium of the two cultivars in this study are within the recommended level or standard ranges. [72] had also indicated that the reduced ratio of sodium to potassium below one is essential to prevent hypertension and cardiovascular diseases before clinical onset.
Copper is used for the synthesis of hemoglobin, proper iron metabolism and maintenance of blood vessels. [73] The Copper content in these two cultivars was found to be 0.52 mg/100 g and 0.66 mg/100 g for hambaguyta and bagana flours, respectively. The results obtained were lower than the reported values for D.alata (2.29 mg/100 g), A.paenophellus (2.18 mg/100 g) and anchote (2.13 mg/100 g) [31,35,69] respectively. However, the values obtained were higher than D. bulbifera (0.22 mg/100 g) as reported by. [46] The results of Magnesium 13.77 mg/100 g for hambaguyta and 25.19 mg/100 g for bagana were lower than other tuber crops including cocoyam (114.89 mg/100 g), D.bulbifera (764.52 mg/100 g) and aerial yam bulbils (758.94-764.52 mg/100 g), as studied by. [29,46,55] The results were in agreement with sweet potato (25 mg/100 g) and cassava (21 mg/100 g) which were reported by. [68] Phosphorus is a crucial element that occurs in almost all foods and important for many normal physiological functions and structures in the human body. [74] Phosphorus concentrations varied widely between the two cultivars 84.72 mg/100 g for hambaguyta and 176.85 mg/100 g for bagana. These values are higher than 27 mg/100 g for cassava and 55 mg/100 g for yam, [68] 34.61 mg/100 g for anchote [52] and 37.8 mg/100 g for D.bulbeifera according to the investigation of. [47] The two cultivar flours have lower phosphorus concentration than the result obtained by [29] for aerial yam tuber (577-1070 mg/100 g). The differences on phosphorus content between the two cultivars of A. abyssinicus could be attributed to different growth conditions, genetic factors, and geographical variations in soil loads of the minerals, efficiency of mineral uptake, and the analytical procedure employed, which indeed should be verified through further study.
Vitamin C has multiple functions needed to maintain the structure of collagen and a type of protein that connects all the tissues of fibers, skin, veins, cartilage, and other tissues in the human body. [36,39] Vitamin C contents of the two cultivar flours were 4.33 mg/100 g and 4.26 mg/100 g for hambaguyta and bagana tuber flours respectively. These values are higher than the values reported by [39] for A. muelleri (0.88 mg/100 g), D.hispida (0.70 mg/100 g) and Homalomena philippinensis(1.14 mg/100 g), but lower than D.bulbifera (12.48 mg/100 g) studied by [40] and okra pod (11.60-27.14 mg/100 g) documented by. [24]

Functional properties
Food functionality refers to the properties of a food ingredient other than nutritional value that have a significant impact on its application and determine how food material is used in various food items. The functional properties such as swelling power, solubility index, water absorption capacity and oil absorption capacity of the two cultivars of A.abyssinicus tuber flours were determined as shown in Figures 3a & 3b.
Swelling power and solubility index reflect the interaction of flour with water. Swelling power is a measure of starch's ability to absorb water and swell, indicating the extent of associative forces within the granules, while solubility is a measure of granule dispersion after cooking. [27,75,76] The swelling power of the two cultivars of A.abyssinicus flours was increased from (5.01-5.70 g/g and 4.93-5.77 g/g) with a solubility index of (17.33-25.33%) and (17.67-25.67%) for hambaguyta and bagana, respectively, at a temperature range of 60-90°C. The swelling power and solubility values were almost similar between the two cultivars, but lower than the values reported by [26,77] for swelling power and solubility of anchote flour which had a value of (9.08 g/g) and (41.53%) respectively. wheat flour (7.5 to 10.8 g/g) and (35.87%) according to the finding of [78] and cassava flour (7.5 to 10.8 g/g) and (32.19%) as studied by. [79] Swelling power is a temperature-dependent phenomena and resistance to swelling has been observed in highly linked starch granules with an extensive and tightly bound structure. [76] As a result, the decreased swelling power found in this study could be attributed to stronger association or bonding forces in the tuber flours' starch granules.
Water absorption characteristics refer to a product's ability to associate with water in situations where water is limiting. Bagana and hambaguyta flours have water absorption capacities of 2.09 g/g and 2.08 g/g, respectively, and oil absorption capacities of 0.91 mL/g and 0.91 mL/g. The WAC of the two flours was higher than cassava flour (1.12 g/g) as studied by [80] and wheat flour investigated by. [26] However, it is lower than the WAC of mucuna flagellipes, which has a value of (3.34 g/g) as determined by researcher. [81] Bagana and hambaguyta flours had lower OAC than anchote (1.92 mL/g) and cassava (2.18 mL/g), according to the finding of. [26] According to, [82] flour with a higher water absorption capacity could be used as a thickening in liquid and semi-liquid foods since it has the potential to absorb water and swell for enhanced food consistency. Since, A.abyssinicus flour had a good water-holding capacity, it is ideal for use as a raw material in bakery products and other applications. OAC is a noticeable factor in food formulations since it improves flavor and increases the mouth feel of meals. The ability of a food component to physically entrap oil through a complex capillary attraction mechanism is crucial for a variety of applications, and this attribute of flour contributes to improved flavor retention, consistency, and mouth-feel. [81]

Conclusion
The two tuber cultivars of A.abyssinicus (Bagana and Hambaguyta) were investigated for their nutritional composition, functional property, phytochemicals, minerals, heavy metals, and vitamin contents. The study revealed that the two cultivars were presented good nutritional composition in terms of crude protein, crude fiber and total carbohydrates. In addition the cultivars showed good water-holding potential that make the tuber ideal for baked and related product developments. The phytochemicals obtained were below the toxicity level recommended by World Health organization except calcium oxalate in which the cultivars cannot be used for human consumption as raw, which needs pre-treatment to reduce to the level of allowed concentration. In terms of mineral content, the cultivars demonstrated as a rich source of magnesium, phosphorus, iron and vitamin C, and presented no detectable amount of heavy metals. Although this tuber cultivars have been neglected and underutilized, the findings of this study has confirmed that the crops can be best alternatives in food formulation and product development and playing a paramount role in full-filling the food and nutritional insecurity. The wild edible tuber (Amorphophulus Abyssinicus) crop of Ethiopia can be used after treatment as supplementary, seasonal, or survival food sources in many cultural groups, and hence play a role in combating food insecurity. Thus, the crops should be properly cultivated with best agronomic practices and improved post-harvest management.