Download complete project materials Assessment Of The Level Of Contamination Of Cow Skin (Kpomo) from chapter one to five
CHAPTER ONE
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INTRODUCTION
1.1 Background of study
Both developed and developing countries have experienced food and lifestyle changes that have led to an increase in demand for processed and preserved foods. These improvements in the food production and processing technologies have increased the chances of contamination of food with various pollutants (Sabir et al., 2003).
Hides are by-products from animals whose primary uses include production of leather, glue and food commonly called Kpomo or ganda in Nigeria (Leather Technology Center, 2002). These hides obtained from slaughtered ruminants are rid of their hair before consumption (Obiri-Danso et al 2008). This could be achieved through either scalding or singeing of the hides.
The scalding involves subjecting the skin to treatment using boiled water. This softens the hair after which it is been shaved using sharp objects. “To singe” is to burn superficially the feathers, bristle or hair of a bird or animal by subjecting it briefly to flame (American Heritage Dictionary, 2008).
This practice of singeing is favoured in African countries as it preserves the carcass hide for consumption and evokes flavour in meat acceptable by the local populace (FAO, 1985). Traditionally, singeing proceeds in open fire using firewood or coal. However, it was noticed recently that in certain parts of Kaduna metropolis that relative scarcity of wood has compelled local butchers to use scrap tyres as alternative source of fuel to singe hides of slaughtered livestock.
The practice though unconventional and potentially dangerous, is increasingly favoured by local butchers; reasons been that fire from tyres is able to selectively burn animal hair without cracking the hide; and also due to the fact that singeing rids hide of hair in lesser time than other methods due to the amount of heat produced by combustion of scrap tyre (Obiri-Danso et al, 2008).
Report on “Air emissions from scrap tyre combustions”, airborne emissions from open tyre fires are estimated to be 16 times more mutagenic than wood combustion and 13,000 times more mutagenic than coal-fired utility emissions. Combustion of tyre produces criteria pollutants such as particulates, carbon monoxide (CO), sulfur oxides (SOx), Nitrogen oxides (NOx), and volatile organic compounds; they also include “non-criteria” hazardous air pollutants, such as polynuclear aromatic hydrocarbons, dioxins, furans, polychlorinated biphenyls (PCB); and metals such as iron, lead, cadmium, nickel, zinc, chromium (EPA, 1997).
The method of processing cow skin (singeing) to “kpomo” using fossil fuels and scrap as fuel is an issue that has not been given the needed attention in the Nigerian food market. There is very little or no chemical investigation into the use of smoke in the processing of the cow skin which is a common practice in Nigeria. (Chen, 1996).
A number of factors related to the smoking process affect the composition of smoke as well as the Polycyclic Aromatic Hydrocarbon uptake in the products, with the combustion temperature being critical (Simko, 2005; Garci and Simal Gándar, 2005; Roseiro et al., 2011). Since the kpomo is for human consumption, an investigation into its level of contamination from processing and its implication on the health of the consuming public is necessary.
1.2 Cow skin (Kpomo) in Nigeria
Kpomo is an important component of household, food security, and income in West and Central Africa. It is an important food source. It is consumed in both rural and urban areas, and can make a significant contribution to the cash income of rural households living in extreme poverty. In Nigeria, Kpomo is widely available alongside domestic meat and fish.
Most consumers in Nigeria prefer the taste of Kpomo than domestic meat and fish, because they are less expensive and are more widely eaten. Kpomo is eaten throughout the year, and its lesser price means that it tends to be purchased in large quantities. Cow skin is mostly sold processed (i.e. dressed and smoked): Singed cow skin has a longer shelf life, but is nearly twice as expensive. Overall, the monthly volume of cow skin sold by retailers is 15,859 kg with a retail value of US$48,000, (Falconer, 1992) subject to seasonal variation.
If additional sources of Kpomo are incorporated (from informal sales, gifts, and personal captures), total kpomo consumption in Nigeria city can be estimated at 21,410 kg per month or about 0.01 kg per person per day (Guy et al., 2004).
Both natural and anthropogenic sources contribute to Polycyclic Aromatic Hydrocarbon (PAH) levels in the environment (Anyakora et al., 2007). Apart from crude oil and petroleum based products which have been found to contribute high amounts of PAHs into the environment, other sources include natural fires, volcanic eruptions, thermal geological reactions, industrial processes, burning and combustion of fossil fuels, exhaust fumes from vehicles, tobacco-smoke, waste incineration, domestic heating using wood, coal and mineral oil (Grova et al., 2002; Anyakora et al., 2007), as well as aluminum production (Wenzl et al., 2006).
1.3 Smoke Processing
Food smoking belongs to one of the oldest food processing technologies which mankind has used for at least 10,000 years. Smoking started to be widely used not only for special organoleptic profiles of smoked products, but also for the inactivating effect of smoke (and heat) on enzymes and microorganisms. This age-old technique of smoking brings desired flavors, improves color and appearance, and has a tenderizing action and preserves foods.
Today smoking technology uses mainly the special effects of various sensory active components (phenol derivatives, carbonyls organic acids and their esters, lactones, pyrazines, pyrols and furan derivatives) contained in smoke for aromatization of meat products to make food with a specific organoleptic profile, widely demanded on the market.
Foodstuffs such as meat and fish and some types of cheese have been smoked in many countries for centuries. Originally, the purpose was to preserve the food; partly by reducing the moisture content and partly through the transfer of anti-microbiological components, such as aldehydes and phenols, form the smoke to the food (Chen, 1996).
Smoking is a processing technique in which meat is exposed directly to wood smoke which may be generated by a variety of methods (Guillen et al., 1997). It has been well documented that the various processing methods such as smoking can induce formation of PAHs in processed foods. Smoked products have traditionally received special attention because considerable amounts of PAH have been detected (Larsson et al., 1988; Gomaa et al., 1993; Karl & Leinemann, 1996).
Karl and Leinemann (1996), asserted that traditional direct smoking, in which the smoke is generated in the same chamber where the product is processed, exposes it to higher PAH content than indirect smoking, which uses a separate chamber for smoke generation. They indicated in their research that in indirect smoking, it is possible to lower PAH load by passing the smoke through filters and washers and even cool the smoke before it comes in contact with the food.
In developed countries, computerized smoking chambers with external smoke generators and temperature control systems have generally replaced the direct smoking systems using traditional kilns. In the developing world and more so in Nigeria, traditional direct smoking systems are almost exclusively used even today.
The most common method of singeing cow skin in Nigeria uses wire gauze on steel drums fueled by wood and/or scrap tyres (Chen, 1996).Smoking food items in uncontrolled processing conditions, characteristic for traditional smoking process, results in high levels of PAHs (Alonge, 1987, 1988; Afolabi et al., 1983; Simko, 2002).
Several processing methods, including smoking, grilling and roasting, have been reported to induce formation of PAHs in foods. Of the various types of foods investigated, processed meat products were found to contain high amount of PAHs (Chen 1996). Thus, the formation of PAHs during processing of foods poses a potential health hazard to humans.
It has been established that raw meat (from animals) does not contain appreciable levels of carcinogenic PAHs and no accumulation along the food chain has been observed for these contaminants in animal fat tissue (European Food Safety Authority, 2008). Nevertheless, the presence of PAHs in Vertebrate fish has been observed.
According to most authors, due to their ability to rapidly metabolize PAHs, fish generally contain very low PAH concentration; even when they come from heavily contaminated areas (Van der Oost et al., 2003).
Smoked and grilled foods may contribute significantly to PAH dietary intake if such foods are part of the usual diet. Long term consumption of traditionally smoked products could be responsible for the higher incidence of liver and stomach cancer in Nigeria. There is limited or virtually no information on the levels of PAHs in smoked fish and meat in Nigeria.
Very limited studies on the monitoring of PAHs in the environment are available. Most studies have focused on other forms of pollution and degradation, but not on PAHs. Some few works on PAHs include those of (Gilbert et al., 2006); Esumang et al., (2009); Joyce et al., (2010).
1.4 Indicator of PAHs in Cow skin
Benzo[a]pyrene has been chosen as the general indicator of total PAHs present in smoked foods. This was done taking account of the situation regarding the presence of PAHs in smoked food and problems in assessing and interpreting correctly.
A maximum acceptable concentration of 1 ngkg-1 benzo[a]pyrene in smoked foods has been set in force since 1973. Afolabi, A.O et al., Adesulu, E.A., et al., Oke, O.L. (1983). In spite of the fact that benzo[a]pyrene constitutes only between 1 and 20% of the total carcinogenic PAHs. Subsequently, other countries such as Austria, Czech Republic, Switzerland, Italy and the Slovak Republic, have also adopted a specification, which requires that the concentration of Benzo[a]pyrene in smoked foods should not exceed 10ngkg-1 (Afolabi, A.O 1983).
1.5 Problem Statement
The consumption of cow skin as “kpomo” in Nigeria is believed to have originated among the poor and uneducated South-Western part of the country, who could not afford the price of lean meat. But the art of processing cow skin for consumption is now popular in most part of the country. Presently, kpomo is a variety among assorted meat and its consumption is no longer by the poor only as it is a popular delicacy among the rich and elites.
Kpomo is fast becoming a mass-consumer product (Leninger, 1977). The consumption pervades ethnicity, religion social status or sex. The poor supplies of hides for shoes and leather related cottage industries can be attributed to the consumption of hides and skin as kpomo by most Nigerians (Leninger, 1977).
The traditional methods of processing cow skin using combustion fumes could introduce high levels of PAH into food. Singeing of cow skin (kpomo) using smoke from burnt car tyres is raising serious concern because of the adverse effects it may have on consumers (Obiri-Danso et al., 2008).
Smoke emanating from the burnt scrap tyres could contribute high levels of PAHs in processed cow skin (kpomo) due to incomplete combustion, high temperatures, oxidation, and physical deposition of soot. There are very little records of systematic clinical studies investigating the levels of contamination of singed cow skin eaten in Nigeria. This research therefore seeks to investigate the levels of PAHs in smoked meat consumed in the country (Guillen et al., 2000).
1.6 Justification
Kpomo is served as delicacy in several parts of Africa including Nigeria. Processing of kpomo includes singeing off the hair of animals in flames by various substances such as wood mixed with spent engine oil, plastics mixed with refuse or discarded car tyres. These materials could easily generate PAHs to contaminate the cow skin.
This presents a significant health hazard to consumers and therefore the need to investigate the levels of PAHs in cow skin in order to assess their suitability for human consumption. Up to date no systematic studies have been carried out on the levels of PAH in kpomo consumed in the country. This research will therefore serve as the baseline for further possible research. It will also form the basis for informed policies to be made on the processing technologies and consumption of “kpomo” in the country.
1.7Aim and Objectives of the Study
The aim of the study is to assess the level of contamination of cow skin by the 16 Criteria Polycyclic Aromatic Hydrocarbon after singeing with scrap tyres and wood as fuels obtained at abattoirs in Kaduna metropolis. This would be achieved using the following objectives:
- To collect, prepare and extract Polycyclic Aromatic Hydrocarbons from kpomo samples singed with scrap tyres and fire wood using mechanical agitation method of extraction.
- To characterize the functional groups, present in the extracts
- To determine the presence of PAH in the six sample types namely: Shaved, unsinged and singed (FW), singed (ST), singed and washed hides (FW) and singed and washed hides (ST)
- To compare the levels of PAH contamination among sample types i.e. unsigned, singed, shaved and singed & washed.
- To compare the difference in level of Polycyclic Aromatic Hydrocarbon contaminations between burnt scrap tyres and firewood.
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