Determination of the Elemental Composition of the Pulp, Seed and Fruit Coat of Black Velvet Tamarind (Dialium guineense) using Instrumental Neutron Activation Analysis

This study sought to provide data on the mineral composition of the fruit pulp, outer coat and seed of Dialiu guineense in an attempt to widen the sources of minerals for the rural population of sub-Saharan Africa. The elemental composition of the pulp, seed and fruit coat of black velvet tamarind (Dialium guineense) was determined using Neutron Activation Analysis. The fruit pulp contained manganese (23.40±1.57μg/g), chlorine (205.40±37.59 μg/g), calcium (5671.00±2132.30 μg/g), sodium (332.95±8.76 μg/g) and potassium (6190.00±711.85 μg/g). The seed and fruit coat contained all these minerals except potassium and sodium respectively. The fruit pulp can serve as a good source of macrominerals for humans while the fruit coat and seed could be ground and incorporated in various meal formulations of livestock as mineral supplements.


INTRODUCTION
It has been reported that millions of people in Sub-Saharan Africa are affected by mineral deficiency (UNICEF, 2009;UNICEF and TMI, 2004).Minerals known to be essential to a healthy body include calcium, phosphorous, cobalt, copper, fluorine, iodine, iron and sodium.The role of these minerals in body metabolism is of prime importance.Their deficiency causes diseases, whereas their presence in excess may result in toxicity to human life (Hashmi et al., 2007).
Black velvet tamarind (Dialium guineense), a forest tree, is well known in many localities especially in West Africa.Small black velvet fruits are characteristic of the genus.The tree grows to about 20 m in height, 0.8 m in diameter, low-branching, rarely straight, bearing a compact densely leafy crown but is often shrubby (Okegbile and Taiwo, 1990;Burkill, 1985;Keay et al., 1964).
There is limited information in the literature about the mineral composition of the various components of the fruits of Dialium guineense except for a partial account by Adepoju (2009).This study therefore, sought to provide data on the mineral composition of the fruit pulp, outer coat and seed of D. guineense in an attempt to widen the sources of minerals for the rural population of sub-Saharan Africa.

RESULTS AND DISCUSSION
NIST Standard Reference Material (SRM) 1547 peach leaves were validated using NIST Standard Reference Material (SRM) 1572 Citrus Leaves (Table 2).The elements in the samples (fruit coat, pulp and seed) were detected using Instrumental Neutron Activation Analysis (INAA) and concentrations were calculated on dry weight basis in triplicate.
The mean elemental composition of the fruit coat, pulp and seed showed the presence of manganese, chloride, calcium, sodium, magnesium and potassium in varying quantities (Table 3).The fruit pulp contained all the minerals of interest in this study; the seed contained all but potassium while the fruit coat lacked sodium.
The results obtained in this present study are comparable to the study by Adepoju (2009) on the pulp of D. guineense.However, owing to the difference in methods used in assessing the mineral composition, the present study gave relatively higher values.
Manganese and magnesium were highest in the seed (574.20±94.17µg/g and 4401.00±321.27µg/g, respectively) as compared to 23.40±1.57µg/g and 910.10±174.74µg/g in the pulp.Dara (1993) asserts that a daily intake of 2.5 to 5 mg of manganese contributes to the well-being of cells.Manganese  deficiency causes diseases and excess of it is known to cause poisoning of the central nervous system.Absorption, ingestion, inhalation or skin contact may cause manganic pneumonia (Underwood, 1997).Magnesium is a very important micronutrient required for bone formation and aids enzyme action and nerve heartbeat functions (Witney and Rolfes, 2005).Calcium was present in all three parts of the fruit (coat, pulp and seed) in varying concentrations; it was highest in the seed (5954.00±2238.70µg/g) and least in the fruit coat (5428±2040.93 µg/g).Calcium is a very important mineral and very essential in human diet.It plays a role in the formation of bones and is also essential for blood clotting and muscle contraction (Wardlaw and Smith, 2006).Its presence in the pulp albeit low is advantageous to the consumer.For adults, daily calcium intake of 1,000 mg is required.In children, this intake is higher.If calcium is taken in low quantities or if it does not meet the body's requirements, the risk of rickets and osteomalacia may increase.
Chlorine, aluminium and vanadium are found in varying amounts in all three parts of the fruit of D. guineense analysed.Chlorine is an essential electrolyte located in all body fluids responsible for maintaining acid/base balance, transmitting nerve impulses and regulating fluid in and out of cells (Anonymous, 2012).Aluminium is thought to be involved in the action of a small number of enzymes such a succinic dehydrogenase and daminolevulinate dehydrase (involved in porphyrin synthesis).However, the body has a hard time ridding itself of excess aluminium (Anonymous, 2012).
Raisins have been reported to contain a similar mineral profile (Ghrairi et al., 2013).However, the levels of these minerals in this present study are higher than the results for raisins.Recent studies in Ghana have shown that the Volta clam (Galatea paradoxa) mantle contains these same elements which were found suitable for human consumption based on the WHO Safety Reference Standards (Serfor-Armah et al., 2010).

CONCLUSION
Calcium, chlorine, magnesium, phosphorus, potassium and sodium are macrominerals required by the body to function properly.Their presence in the pulp of the fruit of Dialium guineense (which is the portion that is normally eaten) and in the seed (except potassium) is an indication that D. guineense can be a good source of these macronutrients.The seeds of D. guineense can be ground and added to the meals of malnourished children to add up to the nutrient requirements.The fact that more than one fruit of D. guineense is consumed at a time will mean that these minerals will accumulate in the body.The fruits of D. guineense are thus recommended as snacks in the Sahelian region of Africa.

Table 1 :
Nuclear data (IAEA-TECDOC-564) for the elements of interest Centre at the Ghana Atomic Energy Commission.The fruits were separated into their component fruit coat, pulp and seed.Each component was then pulverized in a vibrating disk mill.200 mg of each sample was weighed into clean polyethylene films.The films were wrapped and heat-sealed.Three replicate sub-samples were prepared, packed into polyethylene irradiation vials and heat-sealed.
Region of Ghana.This is the main source of the D. guineense fruits in Ghana.After the collection, the fruit samples were taken to the Ghana Herbarium GC, Department of Botany and University of Ghana for identification.All fruits used in this research were ripe and without any visibly identifiable damage or blemish.Sample preparation:Sample preparation was carried out in the sampling preparation room of the Ghana Research Reactor-1 Sample irradiation, counting and analysis: The irradiation and counting of samples have been previously described by Serfor-Armah et al. (2010).

Table 3 :
Elemental composition of the fruit coat, pulp and seed of D. guineense Concentration