Evaluation of Some Heavy Metals Concentrations in Chocolate, Candies and Tomato Puree Imported From China
CHAPTER ONE
AIM AND OBJECTIVES
The aim of this study was to determine some heavy metals (Cu, Mn, Fe, Ni, Zn, Ti
and Cr) which might be essential at low concentrations in some canned tomato paste (testi tomato paste and merysa concentrates de tomato paste) chocolates and candies (lollipop with pencil, milk candy, royal glucose and biscuits) imported from China and to provide data that may be used as the basis for preventive measures. This was set to be achieved through the following objectives:
- To determine the metal contents of canned tomato pastes, lollipop, biscuits, milk candy and chocolates from China sold in Nigeria major markets.
- To compare the levels of the metals in canned tomato paste, lollipop, biscuits, milk candy and chocolates with international standards.
- To determine the risk associated with the consumption of these products.
CHAPTER TWO
LITERATURE REVIEW
ENVIRONMENTAL CONTAMINANTS
Environmental contaminants are substances that originate from diffuse sources and
may appear in food based on their ubiquitous presence in the environment (Klaus et al., 2011). In recent years, it has been emphasized that food safety and transparency of the food-related regulatory process is of pivotal importance to enhance consumer’s confidence in food (Horton, 2001). Compared to other contaminants, heavy metals (HMs) which are widespread and potentially harmful, are not biodegradable and tend to accumulate in living organisms through the food and chain becoming persistent organic contaminants (Fan et al., 2002; Buccolieri et al., 2006). At certain levels, they may cause toxic effect to the organisms (Bryan and Langston, 1992), and are serious threat to the ecological safety and human health.
One of the prices paid by humans in the course of development is pollution in one form or the other. Though not conspicuously alarming, the slow and steady pollution by heavy metals in the environment is quite hazardous (Baskar et al., 1999). Heavy metals arise from unorganised industrial growth and are considered as major pollutants of natural water bodies. Anthropogenic activities like industrial processes, unsafe disposal of industrial wastes, agricultural wastes, and the like release heavy metals into the environment. Once released they contaminate water, soil, plants and enter the food chain, posing health problems to human beings. These recalcitrant pollutants received considerable attention because of their inherent toxicity to living organisms. When they reach the aquatic environment and, being non-degradable remain suspended or partially dissolved in water and subsequently accumulate in aquatic lives (Sharma and Pande, 1998).
Considering the significance of heavy metals and consumption of canned food ingredient and candies, it is necessary to monitor the levels of heavy metals in these commodities.
HEAVY METALS
Increasing industrialization has been accompanied throughout the world by the
extraction and distribution of mineral substances from their natural deposits. Following concentration, many of these have undergone chemical changes through technical processes and finally pass, finely dispersed and in solutions, by way of effluent, sewage, dumps and dust, into the water, the earth and the air and thus into the food chain. Heavy metals are in the water we drink, the foods we eat, the air we breathe, our daily household cleaners, our cookware and our other daily tools. A heavy metal has a density of at least 5 times that of water and cannot be metabolized, therefore accumulate in the body (Sindiku and Osibanjo, 2011).
According to Spiegel (2002), some heavy metals may be important trace elements in the nutrition of plants, animals or humans (e.g. Zn, Cu, Mn, Cr, Ni and V) in very low concentrations while others are known to have negative nutritional effects (e.g. Pb, Cd and Hg). All of these metals may cause toxic effects if they occur excessively. The presence of heavy metals in foods and food products except for accidental or criminal actions reflects the environment (Iwegbue, 2010). Heavy metals in food and food products may originate from natural sources such as soil and water; environmental contamination including fertilizers and pesticides; industrial processing and containers, such as aluminum or tin cans (Coultate, 1992; Vela et al., 1998; Orghêda et al., 2005). The bioaccumulations of these metals over large territories a
CHAPTER THREE
MATERIALS AND METHODS
MATERIALS
Study Area
The study areas include six states across the six geographical zones of Nigeria. One state from each zone was used for the study. The choice of these States was based on availability of the impounded products reported in Thisday 29 September, 2009. The Zones
CHAPTER FOUR
RESULTS
METALS IN CANNED TOMATO PUREE
The results of the levels of heavy metals in two brands of canned tomato puree (Samples A and B) are presented in Figs. 4.1 and 4.2. For sample A, the Cu concentration was highest in Site 3 sample (4.2mg/g), and lowest in Sites 1, 2, 5 and 6 samples (4.0mg/g). Mn concentration was highest in Site 4 sample (42.5mg/g) and lowest in Sites 2 and 6 samples (40.0mg/g). The highest and lowest of Fe were 27.0 (Sites 2 and 6) and 26.0mg/g (Site 5). Ni had highest concentration (56.0mg/g) in sample from Site 5, and lowest (55.0mg/g) in samples from Sites 1 and 4. The highest concentration of Zn (27.8mg/g) was in Site 4 sample while Site 5 sample had the lowest (26.5mg/g). Ti and Cr were not detected in any of the samples.
CHAPTER FIVE
DISCUSSION
METALS IN CANNED TOMATO PUREE
Although heavy metals such as Cu, Zn, Mn, Fe and Ni are essential in human nutrition, their determination in food products is important, since at high concentrations they pose health risk. In the present study, Cu was averagely high in Sample B compared to Sample A. Different sources of the raw tomatoes used in the processing could explain the difference in Cu levels in the two samples. However, due to unavailability of literature values and couple with the fact that there was no well defined limits for these metals in canned tomato puree, studies on vegetables were used for comparison. When the values of Cu were compared with values reported in literature, the values were found higher than 3.03 – 6.24µg/g reported by Fisseha (2002) in vegetable crops. Iyaka (2007) also reported 5.00µg/g which was lower than those reported in this study. Similarly, Mohammed et al
(2003) in their assessment of essential and toxic elements in tomato reported higher levels of 4.3 – 57.1mg/g Cu. Generally, the results obtained in this study are higher than 5.00µg/g recommended limits for Cu (FAO/WHO, 2001).
CHAPTER SIX
CONCLUSION AND RECOMMENDATIONSCONCLUSION
The present study showed that not all the studied metals were found in the samples;
Ti and Cr in samples A and D, Cr in sample C and E, and Fe, Ni and Zn in sample F were not detected. However, all the metals found in a sample were generally higher than reported values for vegetables and confectionery for tomato puree, chocolates and candies. The reasons for the high levels of the metals in the samples could arise from unsafe storage conditions or at any point in the production chain.
Also, evaluation of dietary intake of these products daily revealed that sample A (except for Cu and Fe), B, C (except for Cu), D and E were above the daily dietary recommended limit for all the studied metals. Thus a frequent intake of these contaminated products is likely to induce health effects arising largely from Cu, Mn, Fe, Ni and Zn.
The assessment provides some preliminary evidence that these imported products from China contained unacceptable levels of heavy metals with potential serious consequences for children and adults who consume the products. The results also agree with the argument of NAFDAC and SON of the questionable quality of products imported from China (This Day, 2007) which poses a potentially significant public health threat.
RECOMMENDATIONS
Despite the efficiency of the food regulatory agencies in Nigeria, the importation
and distribution of contaminated foods still continues. However, the agencies should employ the use of portable X-ray fluorescence instruments readily available, as demonstrated by the investigation here, for effective screening of products or confirming contamination by these heavy metals.
Also, more regulatory actions should be taken to restrict consumption of these contaminated foods as the future of any nation depends on the health, prosperity and progress of the forthcoming generation.
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