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Title: Nutritional and Phytochemical Evaluation of Anchote (Coccinia abyssinica) (Lam.) (Cogn.) Accessions to Promote its Contribution for Food Security and Medicinal Use
???metadata.dc.contributor.*???: Prof. Negussie Retta
Prof. Gulelat Desse
Prof. Ali Mohammed
Ayalew, Yenenesh
Issue Date: Dec-2016
Publisher: Addis Ababa University
Abstract: Anchote (Coccinia abyssinica (Lam.) (Cogn.)) is one of the important endemic crops principally grown for its edible tuber throughout the south and southwestern parts of Ethiopia. Moreover, its newly growing leaves along with tendrils are served as vegetable after cooking; making Anchote a double crop. Being one of the underutilized vegetables, there are few research efforts made to comprehensively characterize Anchote germplasm in respect to its nutritional composition, anti-nutritional factors, functional properties, phytochemical composition (qualitative and quantitative) as well as volatile organic compounds. The main objective of this study was, thus, to assess the nutritional profile and phytochemical properties of the edible parts of 44 Anchote accessions. Significant variability was observed in nutrient composition and anti-nutrient content among the tested accessions and plant parts. Leaves were found to be rich in crude protein content (8.96±0.01% - 35.42±0.05%) compared to tubers (5.82±0.00% - 13.72±0.10 %)of 100 g dry matter. In contrast, tubers were found to be superior in utilizable carbohydrates (73.89±0.22% - 84.51±0.43%) of 100 g dry matter, and gross energy (349.14±0.10 - 368.48±0.24) of Kcal/100g dry matter. Other proximate values documented include crude fat (0.24±0.05 - 0.75± 0.07% and 2.44±0.27- 4.68±0.84%); crude fiber (3.63±0.04-6.96±0.24% and 7.89±0.03 -13.05±0.08%) as well as total ash (4.63±0.31 - 6.83±0.02% and 10.74±0.04 - 13.59±0.02%); in tubers and leaves of Anchote, respectively. Total amino acid content of accessions with high protein content ranged from 45.12 to 62.89 g/100g protein for tubers and 67.31 to 75.69 g/100g protein for leaves. Variations in mineral contents namely Sodium (Na), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg), Iron (Fe), Cooper (Cu), Zinc (Zn), Manganese (Mn) and Boron (B)were also recorded among accessions and plant parts. The Ca content of tuber ranged from 80.64–372.16 mg/ 100g and for leaf, it ranged from 64.10 –226.95mg/ 100g. The Fe content ranged from 0.39–2.92 mg/100g for tuber and 1.58 – 18.65mg/100g for leaf while Zn content of tuber ranged from 0.22–0.53mg/100g and 0.32 – 3.41mg/100g for leaf. The mean antinutritional contents of tuber samples were: phytate (131.10mg/100g), tannin (112.02mg/100g) and cyanide (13.08mg/kg). For leaves, the contents were phytate (250.30 mg/100g), tannin (216.53 mg/100g) and cyanide (12.36 mg/kg). The levels of antinutrients in leaves were higher than in tubers. On the other hand, the levels of potentially toxic elements such as Cd, As, and Pb were almost negligible, with mean concentration values of 0.86, 0.83 and 7.05 ng/g, and 1.29, 2.62 and 13.53 ng/g in tubers and leaves, respectively. The mean molar ratios for phytate: calcium, phytate: iron, phytate: zinc and phytate x calcium: zinc was 0.05 and 0.11, 3.81 and 4.31, 27.79 and 22.47 and 142.20 and 90.72 in tubers and leaves, respectively. Chemical composition and functional properties of leaf protein concentrate (LPC), tuber and leaf powder of Anchote were also analyzed. Heat coagulation at natural pH was used to obtain the LPC from the aqueous fresh leaf extract. The mean crude protein content for LPC was 47.46 g/100gand its mean total amino acid content was 99.64 g/100g protein. Lowest protein solubility of Anchote LPC (11%) obtained in pH ranges of between 6 and 10 and highest solubility (19%) recorded at pH 12. The result for in-vitro protein digestibility was 57.44±1.48 % for tuber powder, 49.46±1.68% for LPC and 40.92±0.54 % for leaf powder. Leaf powder revealed highest water (2.94 g/g) and oil (1.29 g/g) absorption capacities (WAC & OAC), and lowest value of WAC (1.61 g/g) was observed in LPC. Emulsification reduced with increase in protein concentration and increased with increase in pH in all tested samples. The foaming capacity was highest in leaf powder followed by LPC. Anchote accessions were also tested for presence of some phytochemicals using qualitative and quantitative methods. Qualitative test was done for 12 phytochemicals using seven extraction solvents. Secondary metabolites including total phenols, total flavonoids, crude saponins and betacarotene were analyzed quantitatively. Positive results were observed during qualitative screening for five phytochemical compounds tested in tubers whereas only two tests were positive for leaves in all the seven solvent extracts. Water extract showed positive results for 11 phytochemicals while n-butanol extract showed positive results for six tests for both tuber and leaf samples. The water extract of Anchote showed highest number of phytochemicals in both tuber and leaf parts when compared to other solvent extracts. Anchote leaf had higher total phenol and flavonoid contents followed by fruit and the least concentration of these compounds occurred in tuber for all the tested accessions. Leaf of Anchote contained the highest percentage of saponins (27.65%) compared to other parts. The β-carotene content of Anchote leaf ranged from 25.90.03 to 35.20.16 in μg/g. Anchote leaf and tuber powder samples were extracted by simultaneous steam distillation and solvent extraction (SDE) to determine volatile organic compounds. The extracts were characterized by gas chromatography-mass spectrometry (GC/MS). Thirty volatile compounds from leaves and 15 compounds from tubers were identified with a yield of 770.57 mg/kg and 4536.91 mg/kg, respectively. In conclusion, the study showed that both the tuber and leaf parts of Anchote have appreciable amount of different essential nutrients. Leaves have relatively higher nutrient composition in all accessions compared to tubers, which provides a good scientific evidence to diversify the consumption habit of indigenous people who are growing Anchote mainly for its tuber, the principal edible part of the crop. The different functional properties of Anchote LPC also suggest its potential to be used as an ingredient in processed foods. Anchote is also rich in different phytochemicals and volatile organic compounds that make the plant a potential crop to be used in pharmaceuticals and food industries.
Description: Submitted for the Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Food Science and Nutrition
Appears in Collections:Thesis-Food and Nutritional Sciences

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