Nutritional Quality, Antioxidant Properties, Functionaland Oil Characteristics of Indigenous Okra (Abelmoschus esculentus) AccessionsGrown in Benishangul Gumuz Region, Ethiopia
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Date
2017-07
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Addis Ababa University
Abstract
Okra, a high nutritional potential, is one of the underutilized indigenous vegetables in Ethiopia.
Lack of scientific information on the nutritional quality, phytochemical and oil properties of okra
is a major constraint in its utilization in Ethiopia. This has worsened the already existing ever
increase growing gap between human population and food supply. A food based-intervention
specifically dietary diversification is an affordable and sustainable strategy to meet the demand
of adequate food supply and population growth. One way of ensuring dietary diversity is to
search and promote underutilized indigenous plant species such as okra.Therefore, the overall
objective of this study was to determine nutritional quality, antioxidant properties, functionaland
oil characteristics of pods and seeds of eight okra accessions grown in Assosa Agricultural
Research Center in Benishangul Gumuz region, Ethiopia. The effect of different traditional
processing methods on nutritional, antioxidant and functional properties of the pods and seeds of
selected okra accessions was also evaluated. The germplasm of okra accessions was collected from different agroecologicallocations in the
region by Assosa Agricultural Research Center in 2012 and 2013 harvesting seasons andplanted
on the research center plot under similar agronomic practice and management conditions during
the 2014 main cropping season.The pods and seeds of eight okra accessions, namely OPA#1,
OPA#2, OPA#3, OPA#4, OPA#5, OPA#6, OPA#7, and OPA#8 were collected from the center
plots during the 2014 main okra harvesting season. The analyses were carried out using different
official standard procedures and analytical grade chemicalreagents. The pods and seeds of okra
accessions were then characterized for its proximate composition, mineral contents, antinutritional factors, phytochemical profiles, physicochemical properties, and functional
properties. The proximate composition in g/100gon dry weight basis of the pods and seeds of okra accessions varied significantly (P<0.05) from one accession to anotherand had the following ranges in pods and seeds respectively moisture 9.69-13.33 and 9.27-12.70; crude protein 10.25- 26.16 and 22.51-38.09; crude fat 0.56-2.49 and 18.64-36.84; crude fibre11.97-29.93 and 1.94- 5.96; total ash 5.37-11.30 and 4.53-6.05; utilizable carbohydrate 36.66-50.97 and 18.69-37.77. The gross energy ranges from 216.60-280.63 and 324.88-423.84 kcal/100g in pods and seeds respectively.The minerals in mg/100g ofpods and seeds of okra accessions also ranges from one
accession to another calcium 111.11-311.95 and 66.37-103.66; iron 18.30-36.68 and 8.33-20.29;
potassium 122.59-318.20 and 90.00-187.92; zinc 3.83-6.31 and 3.92-6.42; phosphorus 25.62-
59.72 and 516.94-1497.23 and sodium 3.33 to 8.31 and 15.06-27.81. The Na/K, Ca/P, Ca/K and
Fe/Zn ratios of the pods and seeds of okra accessions, respectively were 0.025-0.290 and0.179-
0.416; 2.605-11.312 and0.058-0.146; 0.507-1.753 and 0.399-0.999; and 3.239-9.611 and 1.297-
4.806. The principal component analysis had shown a nutritional variability and five independent
clusters in the pods and seeds of okra accessions and this may be useful to breeders for
improvement of accessions based on the desired trait.The antinutrient in mg/100g of pods and
seeds of okra accessions ranges from one accession to another. Phytate 0.83-0.87 and 0.39-0.46;
tannin 4.93-9.90 and 0.71-3.78 and oxalate 0.04-0.53 and 0.74-0.75. The molar ratios of pods
and seeds in this study were below the critical/ standard value.Particularly, pods and seeds of
OPA#6 accession contained a significantly ((P<0.05) high amount of crude protein, ash, crude
fat, calcium, iron and zinc contents.
The pods and seeds of okra accessions had total phenol (mg GAE/g) ranges from 28.10-95.21
and 21.28-57.34 and total flavonoid (mg CE/g) 8.18-18.72 and 10.73-29.04. The EC50 values
(mg/ml) of pods and seeds of okra accessions are as follows: DPPH scavenging2.10-10.30 and
3.1->12; reducing power 1.20-4.20 and 1.18-4.30; metal chelating 0.50-1.52 and 0.32-1.11; and
ABTS scavenging 0.31-1.33 and 0.07-1.5, respectively. The antioxidant activity of both pods and
seeds of okra accession OPA#6 was high in all assays except ABTS scavenging activity for pod
accessions with lower EC50 values and thus can be considered as a potentially rich source of
natural antioxidants and used in functional food application.
The crude oil yield of the eight okra seedaccessions was significantly (P<0.05) varied and ranged
from 19.25-38.19%. Compared with other vegetable oils, the present study revealed that okra
seeds could be considered as potential sources of edible oil specifically the seed of OPA#2
accessions.The physicochemical properties of the okra seed oils varied significantly (P<0.05)
from one accession to another except the saponification value. The values for the
physicochemical properties are0.904-0.923 (specific gravity), 1.460-1.466 (refractive index),
1.315-5.055 (acid value), 2.990-9.060 (peroxide value), 100.45-132.92 (iodine value) and
188.97-194.78 (saponification value).Functional properties of the mucilage of okra pods varied
significantly (P<0.05) and had respective ranges of bulk density 0.58 to 0.64 g/ml; water
absorption capacity 2.45 to 4.60 ml/g; oil absorption capacity 0.02 to 3.64 ml/g; emulsifying
capacity 42.22 to 74.45%; emulsion stability 42.22 to 74.45%; foaming capacity 50.51 to
62.50% and foam stability 36.04 to 54.35%. Total phenolic and flavonoid contents of the
mucilage of the pods of okra accessions ranged from 4.66 to 49.93 mg GAE/g and 8.18 to 18.72
mg CE/g, respectively. The effective concentration (EC50) values (mg/ml) of mucilage of okra
pods ranged from 3.15- 6.60 and 1.10-1.85 for DPPH scavenging and metal chelating effect,
respectively.Particularly, mucilage of the pods from OPA#5 and OPA#7 had desirable water and
oil absorption capacities, whereas the mucilage of accession OPA#1 and OPA#6 had high
emulsifying and foaming properties. Sun drying significantly (P<0.05) reduced the crude protein and crude fat contents of the pods by 7.53 and 34.94%, respectively,but increased the crudefibre and ash content of the pods by 27.90 and 20.44%, respectively. Soaking significantly (P<0.05) reducedthe crude protein, crude fibre, zinc and total phenolic content of the seeds by 3.68, 21.22, 9.03 and 21.03%, respectively. Germination significantly (P<0.05) increased the crude protein, crudefibre, total phenolic and total flavonoid content of pods by 3.68, 16.25, 17.32 and 15.12%, respectively, butreducedthe crude fat and zinc content of seeds by 17.65 and 34.89%, respectively. Roasting significantly (P<0.05) reduced crude protein,crude fat and crude fibre content seeds by 23.97, 31.49 and 50.86%, respectively, but it increased ash, total phenolic and total flavonoid content by 15.34, 14.89 and 14.12%, respectively.The flour of raw and processed pods and seeds of okra was found to exhibit good functional properties and can offer a great potential in various food applications. Generally, the results of this research indicated that indigenous Ethiopian okra contains essential nutrients and phytochemicalsas compared to the commonly consumed green vegetables in Ethiopia such as cabbage, Ethiopian kale, lettuce, swiss chard, carrot, tomato, and celery. The mucilage of the pods and the oil characteristics of the seed accessions were found to exhibit good functional properties and can offer a great potential in various food systems. Hence, increasing the cultivation, promotion, and consumption of underutilized indigenous Ethiopian okra in the country couldhelp to mitigate food insecurity and alleviate malnutrition in the country. Further studies are recommended to determine the active ingredients and specific health benefits for the potential industrial use of the okra.
Key words: Okra; Pod; Seed; Accessions; Nutritional; Phytochemical; Oil; Mucilage; Processing
Description
Keywords
Okra; Pod; Seed; Accessions; Nutritional; Phytochemical; Oil; Mucilage; Processing