CONCENTRATION OF Cu AND Zn IN SOME FRUITS AND VEGETABLES COMMONLY AVAILABLE IN NORTH-CENTRAL ZONE OF NIGERIA.

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1 ISSN: CONCENTRATION OF Cu AND Zn IN SOME FRUITS AND VEGETABLES COMMONLY AVAILABLE IN NORTH-CENTRAL ZONE OF NIGERIA. Y. A. Iyaka Department of Chemistry, Federal University of Technology, Minna, Niger State, Nigeria. Abstract Fruits and vegetables constitute the lowest cost source of essential trace elements for the majority of people in developing nations. Cu and Zn contents were determined in duplicates in twenty selected samples of fruits and vegetables found in North-central zone of Nigeria. These fruits and vegetables include; apple, banana, carrot, cucumber, garlic, grape, green peas, irish potato, lemon, lettuce, okra, orange, onion, paw-paw, pepper, pineapple, spinach, sweet potato, tomato and water melon. The Cu concentration varied from ppm in fruit and from ppm in vegetables, while the Zn levels were ppm and ppm in fruits and vegetables respectively. The Cu and Zn contents obtained showed that fruits and vegetables from this part of the globe could serve as good dietary sources for essential trace metals, and the levels are within safety baseline content for human consumption. Keywords: Cu, Zn, fruits, vegetables, Nigeria. Introduction Fruits and vegetables offer the most rapid and lowest cost source of providing vitamins, fibers and minerals to the majority of people in developing nations. Fruits are palatable, and are often taken in large quantities, while the vegetables are usually consumed in relatively small amounts as side-dish or relish with the staple foods. However, nutritional metals such as Cu and Zn do occur naturally in fruits and vegetables as essential trace elements needed for good health, but they could be toxic when their concentrations exceed limits of safe exposure [1,2].

2 In addition to toxicity problems, Cu and Zn deficiency may also be experienced; hence, Iyengar [3]stated that knowledge of heavy metal contents in crops is important for the identification of adequate, subadequate and marginal intake levels for humans and animals, so that diseases related to trace element deficiency can be overcome. Large number of symptoms/ailments comprising anaemia, depressed growth, dermatitis, dwarfism, electrolyte-imbalance, gastro-intestinal and neurological disorders, lethargy and nausea have been associated in humans with Cu and Zn deficiency, as well as with toxicity due to excessive intake [4,5,6,7]. Furthermore, presence of trace elements in fruits and vegetables has been ascribed to their absorption from the soil and sources such as type of fertilizer, agricultural chemicals and contaminating dirts [8]. Other sources of heavy metals contamination of most foodstuffs may also include adaptation of mechanized farming, sprays, seed preservatives [9], and components from global pollution. Hence, the need to determine and/or monitor the Cu and Zn contents of fruits and vegetables become imperative due to their principal role as essential or detrimental trace elements. A survey of the literature indicates that such a study is scarce, particularly in North-central zone of Nigeria. Previous studies by Bonire et al.[10], Nwaedozie [11] and Iyaka et al.[12]on heavy metals in food in Northern Nigeria were focused on staple foodstuffs. The aim of this study, therefore, is to determine the Cu and Zn contents of some fruits and vegetables commonly available in North-central zone of Nigeria. This research also aimed at providing a baseline data on Cu and Zn levels in fruits and vegetables in the zone. Materials and Method Different samples of the commonly available fruits (Table 1) and vegetables (Table 2) were purchased from central markets of Minna in North-central zone of Nigeria. Samples were analysed as purchased in the fresh forms. The pretreatment of the samples was done by crushing with a porcelain mortar and pestle or by blending to give a homogenized paste. Table 1. Copper and Zinc contents (ppm) of Fruits Sample Cu Zn Apple (Malus pumila) Banana (Musa acuminata) Grape (Vitis vitifera) Lemon (Citrus limonum) Orange (Citrus sinesis) Pawpaw Pineapple Watermelon (Citrullus lanatus) Mean Range mL HNO 3 was added to 10.0g of the sample portion, and allowed to stand for 15min. The mixture was heated until the liquid reduced to 5mL. After cooling,20mlhno 3,10mLH 2 SO 4 and 8mLH 2 O 2 were added and the contents were 2151

3 evaporated to 5mL. After cooling, to eliminate residual acid, 10ml deionized H 2 O was added and the mixture was boiled for 10min (this was repeated twice). After cooling the digest was filtered into 25mL volumetric flask and made up to mark with deionized H 2 O. The digestion solutions were subsequently analysed for Cu and Zn using a Unicam 969 Atomic Absorption Spectrophotometer Solar in the flame mode. Table 2. Copper and Zinc contents (ppm) of vegetables Sample Cu Zn Carrot (Dancus carota) Cucumber (Cucumis sativus) Garlic (Allium sativum) Green peas (pisum sativum) Irish potato (Solanum tuberosum) Lettuce (Lactuca scariola) Okra (Hibiscus esculentus) Onion (Allium cepa) Pepper (Capsicum annuum) Spinach (Basella rubra) Sweet potato (Impomoea batatas) Tomato (Lycopersicon esculentum) Mean Range All samples were analysed in duplicate and three quality control samples consisting of a reagent blank, sample duplicate and spiked sample were run for every batch of 5 samples. Mean fractional recoveries were satisfactory, being in excess of 90% for Cu and Zn analysed. Results The Cu and Zn contents obtained for the fruits and vegetables analysed are given in Tables 1 and 2. The lowest Cu level found in fruits was in pineapple (1.7ppm) and the highest Cu value was in grape (3.0ppm), while the other fruits analysed had Cu range value of ppm. The Zn contents in fruits were generally higher than the Cu concentrations; ranging from 3.8ppm in watermelon to 6.7ppm in apple. Except for watermelon and grape, the Zn levels were twice or more as much as the Cu contents in fruits of this study. The Cu concentrations in the vegetables were similar to those of the fruits; ranging generally from 1.6 to 3.1ppm. Of the vegetables analysed carrot, cucumber and onion had Cu levels of less than 2.0ppm, green peas had the highest value of 3.1ppm and the remaining vegetables samples had Cu content range of ppm. The lowest Zn content in vegetables was in carrot (4.0pm) and the highest content was in spinach (7.0ppm). About 58% of all the vegetables analysed had Zn concentrations of greater than 6.0ppm, hence revealing higher Zn contents than found in fruits. Discussion The results obtained for Cu concentrations in fruits in this study(table 1) are higher than ppm reported as normal range for Cu levels in fruits[13], and also higher than Cu 2152

4 contents obtained in most of the fruits studied by Onianwa et al.[14]in their estimation of the adult dietary intakes of Cu and Zn contents of Nigerian foods using samples purchased from market in the city of Ibadan, South western Nigeria. These differences in Cu contents may be ascribed to variation in composition and soil types. Kabata-Pendias and Pendias [15] observed that, although the relationship may differ according to the plant species and tissue, but plant metal contents are generally a function of the metal concentration in the soil or in the growth solution. Green peas had the highest Cu level for all the vegetables analysed(table 2). This was similar to the findings of Johnson [13] who reported the highest Cu content range for green peas among other vegetables in her table of Cu levels in human foods. The Cu concentrations in carrot, onion and potatoes in this study are lower than 5.0ppm, 5.8ppm and 7.5ppm respectively reported for the same kind of vegetables by Pinochet et al.[16] in their study of long term impacted soil in the Valparaiso region at Chile. Furthermore, higher Cu values than obtained in this study have been reported for cucumber, tomato and spinarch by Mohammed et al.[17] in their assessment of essential and toxic elements in some kinds of vegetables found in Saudi Arabia. The mean Zn content of 5.9ppm obtained for vegetables of this study is higher than 2.1ppm, documented for vegetables in composite group of Canadian foods[13]. Moreover, on specific vegetable specimen, Hussein and Bruggeman [18] had determined Zn content of 7.66ppm in potatoes, in their analyses of Egyptian foods; a value higher than 6.7ppm obtained in this study. Mohammed et al.[17] also obtained Zn concentrations of twice or more values than observed in this study for cucumber, tomato, carrot, lettuce and onion in their analysis of trace elements in vegetables from Al-Taif district. Conclusion The concentrations of Zn in fruits and vegetables analysed in this research were generally higher than the corresponding Cu contents. The results obtained also compare favourably with the findings of the other researchers from other parts of the world. Furthermore, the levels of Cu and Zn obtained do not appear to pose any serious health hazard problem of concern yet, but, the study has helped to show that fruits and vegetables from this part of the globe could serve as good dietary sources for essential trace metals, since their deficiency or toxicity in humans may result in severe health consequences. REFERENCES 1. C. Reilly. Metal Contamination of Food. 2nd ed. Elsevier Applied Science, London(1991) 2. I. M.Skurikhin. Method of Analysis for Toxic Elements in Foods. Part iv. General Method of Ashing for the determination of Toxic elements. Journal of AOAC International 76, (1993) 3. G. V. Iyengar. Elemental Analysis of Biological Systems. Vol. 1. Biomedical, Environmental, Compositional and Methodological aspects of Trace Elements. P CRC Press, Boca Raton, Fl (1989) 4. E.Somer Toxic potential of trace metals in foods. A review. Journal of Food Science. 39, (1974) 5. 5.G. G.Graham, A.Cordano. Copper deficiency in human subjects. In S. A. Prasad,& D. Oberleas. The Nutrition Foundation. Trace elements in human health and diseases. Vol. 1. Zinc and Copper. Academic Press, New York (1976) 6. A. S. Prasad In The Nutrition Foundation. Trace elements in human health and diseases.(s.a.prasad & D.Oberleas,eds) Academic Press, New York (1976) 2153

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