Comparative Analysis of Heavy Metals in Processed Tomato Paste and Fresh Tomatoes Sold in Markets in Ibadan, Nigeria

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1 The Polytechnic Journal of Science and Technology PJST. Vol ISSN: Journal of Science & Technology Polytechnic Ibadan, Nigeria Comparative Analysis of Heavy Metals in Processed Tomato Paste and Fresh Tomatoes Sold in Markets in Ibadan, Nigeria Adegbola, R. A. Chemistry Department, The Polytechnic, Ibadan Abstract Levels of heavy metals in tinned, sachets, tomato pastes and fresh tomatoes sold in markets in Ibadan, Nigeria were evaluated by Atomic Absorption Spectrophotometry. The result obtained for tinned tomatoes were: iron, µg/g; lead, µg/g; chromium, µg/g; copper, µg/g; nickel, µg/g; zinc, µ g/g; calcium, µg/g and cadmium, µg/g. The mean values for sachet tomatoes were: iron, µg/g; lead, µg/g; chromium, µg/g; copper, µg/g; nickel, µg/g; zinc, µg/g; calcium, µg/g while cadmium was not detected. The mean concentration values in fresh tomatoes sold in markets and farm land were: iron, µg/g; lead, µg/g; chromium, µg/g copper, µg/g; nickel, µg/g; zinc, µg/g; calcium, µg/g while cadmium was not detected in all fresh and farm land samples. These values indicate that levels of investigated metals in the analyzed tomatoes were below the permissible levels of metals recommended as dietary intake in tomato. Keywords: Atomic Absorption Spectrophotometry, Heavy metal and Tomato. Introduction Functional food is any fresh or processed food claimed to have a health promoting and/or disease-preventing property beyond the basic nutritional function of supplying nutrients (Harmanescu et al., 2007). Previous reports have linked intake of fruits and vegetables with reduced risk of chronic diseases like cardiovascular disease and cancer. (Sies and Stahl, 1995; Steinmetz and Potter, 1996; Franceschi et al.,1998). Vegetables like tomatoes (Solanum lycopersicum) are very important sources of microelements for human nutrition (Yi-fang et al., 2002) and are also abundant sources of 53

2 Comparative Analysis Of Heavy Metals In Processed Tomato Paste And Fresh Tomatoes Sold In Markets In Ibadan, Nigeria antioxidants and minerals (Toor et al., 2006). Tomato sauce and similar products are widely used for colouring and taste enhancement of various food products. Apart from their taste properties they also have a high nutritive value due ti the content of easily retainable sugars, vitamin C, carotenoids and mineral salts. Tomato sauce is a produce conserved through decrease in humidity, thus preventing the evolution of microorganisms (David et al., 2008). Essential metal macroelements present in vegetables are Na, K, Ca and Mg. The microelements are: Fe, Mn, Cu, Zn and Co. The microelements can be toxic in high quantities. Other metal microelements: Hg, Cd, Cr, Ni and Pb are very toxic. Metal microelements can affect the biological and biochemical processes: nutrition, photosynthesis and respiration (Gergen et al., 2006). Epidemiological studies have shown that the consumption of tomatoes and tomatoes products can help to prevent various forms of cancers, especially prostate cancer, and heart diseases. Heavy metals are non-biodegradable and persistent environmental contaminants, which may be deposited on the surfaces and then absorbed into the tissues of vegetables. Plants take up heavy metals by absorbing them from deposits on the parts of the plants exposed to the air from polluted environments as well as from contaminated soils (Kachenko and Singh, 2006). As a result of urbanization and increasing anthropogenic activities, the heavy metal pollution of soil, water and atmosphere, represents a growing 54 environmental problem affecting food quality and human in cities. Sources of heavy metal in city environmental include domestic and industrial wastes, traffic emissions, agricultural activities, mining and metal works (Nriagu, 1990). Consumption of vegetables is one of the pathways by which heavy metals enter the food chain. Prolong consumption of unsafe concentrations of heavy metals through foodstuffs may lead to the chronic accumulation of heavy metals in the kidney and liver of humans causing disruption of numerous biochemical processes, leading to cardiovascular, nervous, kidney and bone diseases (Sharma et al., 2009). The monitoring of heavy metals in food stuffs is therefore of great importance in protecting the public from hazards of toxic pollution (Onianwa et al., 2001). The present study evaluated and compared the level of heavy metals in processed tinned and sachet tomatoes and fresh tomatoes popularly sold in markets in Ibadan, Nigeria. Materials and Method Sampling A total of thirteen different brands of tinned tomatoes and four of the brands that are packaged in sachets were randomly purchased from three popular markets (Bodija, Sango and Dugbe) in Ibadan, South Western, Nigeria. Fresh tomatoes were also procured from four different markets in Ibadan (Apete, Sango, Bodija, Omi-Adio) and a farm in Omi- Adio. The farm samples served as control. Fresh tomatoes were cleansed

3 with soap and rinsed thoroughly, sliced and oven dried at 105 o C for 24hours prior digestion. Sample Digestion and Heavy Metal Analysis: One gramme of oven-dried, ground sample of each type of brand was weighed into a 50cm 3 beaker. This was followed by the addition of 10cm 3 mixtures of analytical grade acids HNO 3 and HCIO 4 in the ratio 3:1. The beaker was covered with watch glasses and left overnight. Digestion was done on a hot plate at 90 o C in a fume cupboard until about 4cm 3 of the mixture of the mixture was left in the beaker. A further 10cm 3 of acid mixture was then added and evaporated to a volume of about 4cm 3 while still on hot plate, giving a clear solution. The mixture was cooled to room temperature and the solution filtered using filter paper and made up to a final volume of 50cm 3 with distilled water in a volumetric flask. These were stored in polythene bottles till analysis (Yusuf et al., 2002). Eight heavy metals (Fe, Pb, Cr, Cu, Ni, Zn, Ca, and Cd) were analysed in the samples using Buck Scientific Model version (210/211) VGP Atomic Absorption Spectrophotometer. Determinations were done in triplicates. The result was subjected to statistically analysis using One-way ANOVA. Results and Discussion Table 1: Heavy Metals Concentration (µg/g) in Tinned Tomatoes from Three Popular Markets in Ibadan Metropolis. Sample Fe Pb Cr Cu Ni Zn Ca Cd TNV TNP ND TNR ND TNG ND TN ND TN TN ND TN ND TN ND TN ND TN ND TN ND TN ND Key: TNV 1, TNP 2, TNR3, TNG 4 were codes for tinned tomato paste that have sachet paste while TN 5 to TN 13 were codes for tinned tomato paste that do not have sachet paste. Values are means of triplicate determinations. ND means not detected. 55

4 Comparative Analysis Of Heavy Metals In Processed Tomato Paste And Fresh Tomatoes Sold In Markets In Ibadan, Nigeria Table 1 shows the heavy metals concentration (µg/g) in tinned tomatoes from three popular markets in Ibadan Metropolis. The results indicated that Iron ranged from ; lead ranged between ; chromium, ; copper, ; nickel, ; zinc ; calcium ; cadmium was detected only in samples TNV 1 and TN 6 at In all the samples iron and calcium have the highest concentration in sample TNG 4. Table 2: Heavy Metals Concentration (µg/g) in Sachet Tomatoes from Three Popular Markets in Ibadan Metropolis Sample Fe Pb Cr Cu Ni Zn Ca Cd SNV I ND SNP ND SNR ND SNG ND Key: SNV 1, SNP 2, SNR 3, SNG 4 were codes for sachet tomato paste that have tinned paste. ND means not detected Table 2 shows the heavy metals concentration (µg/g) in sachet tomato from three popular markets in Ibadan Metropolis. The level of concentration of metals in sachet tomato pastes in µg/g were: Iron, ; lead, ; chromium, ; copper, ; nickel, ; zinc, ;. calcium, ; cadmium was not detected in all the samples. Calcium has the highest concentration in sample SNG 4. All the samples have concentrations that were below the permissible levels of metals recommended by W.H.O. in tomato Table 3: Heavy Metals Concentration (µg/g) in Fresh Tomatoes Sold in Popular Markets and a Farm in Ibadan Metropolis. Sample Fe Pb Cr Cu Ni Zn Ca Cd FT Apete M ND FT Sango M ND FT Bodija M ND FT Omi-Adio M ND FT Omi Adio F ND Key: FT stands for fresh tomato fruits: M indicates market while F indicates Farm ND means not detected 56

5 Table 3 shows the heavy metals concentration (µg/g) in fresh tomato sold in different markets and a farm. Iron ranges from ; lead ranges between ; chromium, ; copper, ; nickel, ; zinc, ; calcium, ; cadmium was not detected in all the samples. Calcium has the highest concentration in sample from Omi-Adio farm but lowest concentrations of lead, copper and zinc, while chromium, nickel and cadmium were not detected in the farm sample. Lead, chromium, nickel in the samples may be due to the presence of the metals in soils of the farms on which they were planted and also the transportation system since the level in sample obtained from Omi-Adio farm is lower than Omi-Adio market. All the samples have concentrations that were below the permissible levels of metals recommended as dietary intake in tomato: iron 30mg/kg day, lead 1.0mg/kg/day, cadmium 0.03mg/kg/day, nickel 25/35ug/kg/day, zinc 20mg/kg/day. From the statistical analysis of both the tinned, sachet and fresh tomatoes the result showed significant difference (P<0.05) in the concentration of the following metals calcium, zinc, copper, chromium and iron; while cadmium, nickel and lead showed no significant difference (P<0.05). The result of this study is in agreement with results obtained by Harmanescu et al.,(2007) in tomato sauce where cadmium and chromium were not detected but iron showed higher concentrations in two samples (14.81 and µg/g 57 respectively) while other metals have close range to the ones obtained in this study. The work of David et al., (2008) on canned tomato paste showed high values in iron ( ppm), it was reported that though iron is beneficial to the human body it may become an energetic catalyst for some chemical or biochemical processes at very high concentration. However, Jacob and Kakulu (2012) was at variance reporting very high concentration of lead, cadmium, nickel and chromium in all samples including the control samples. Conclusion Maximum limit set by legislation are not exceeded either in the case of tinned, sachet tomato pastes and fresh tomatoes. Calcium and iron which are beneficial metal were higher than the toxic ones. The mean concentrations of all toxic metals were lower in samples directly from the farm. The mean concentration of Cd, Ni and Pb in all the samples of tomato paste were not significant (p>0.05). Ca, Cu, Cr, Fe and Zn showed significant difference between mean concentrations of samples ((P<0.05). The level of metals in the three groups of the samples follow this trend: tinned >sachet> market> farm. Fresh tomatoes from the farm should be on the preferred scale and therefore all the populace are advised to go back to the era of backyard farming to sustain food security. To reduce the pollutant in fresh tomatoes there should be improvement in our transportation system and handling of farm produce to reduce introduction of heavy metals. For processed tomato paste, industries should also used sachet instead of tinned packaging.

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