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ABSTRACT

X–Ray Fluorescence analytical technique (XRF) was employed for the screening of
samples of canned sardine fish and canned tomato pastes for the concentration
levels of trace elements in them. The results obtained revealed the presence of Br,
Cu, Fe, Nb, Ni, Zn and Zr in the two canned sardine fish samples while in the four
brands of canned tomato pastes, As, Br, Cr, Cu, Fe, Pb Ti, V and Zr were detected.
All the elements detected showed concentration levels that are very high and far
above the maximum limits set by most Countries, Health Agencies and International
Organisations. This implies that their level of safety to humans is low and can
constitute a threat to human health. It is therefore important to continuously monitor
these products and their consumption since they are widely consumed in Nigeria.
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TABLE OF CONTENTS

Title page ………………………………………………………………………………. i
Declaration………………………………………………………………………………. ii
Certification………………………………………………………………………………. iii
Dedication ………………………………………………………………………………. iv
Acknowledgement……………………………………………………………………… v
Abstract …..………………………………………………………………………………. vii
Table of Contents ……………………………………………………………………… viii
List of Tables …………………………………………………………………………… xi
List of Figures …………………………………………………………………………… ix
Abbreviations …………………………………………………………………………… x
Chapter 1: INTRODUCTION………….…………………………………………………1
1.1 Statement of the Problem……………………………………………….………..2
1.2 Trace Elements……………………………………………………………………2
1.2.1 Definitions………………………………………………………………………… 2
1.2.2 Classifications…………………………………………………………………… 3
1.2.3 Sources…………………………………………………………………………… 4
1.3 Canned Foods……………………………………………………………….. 8
1.3.1 Sardines…………………………………………………………………………… 9
1.3.2 Tomatoes…………………………………………………………………………. 10
1.4 Aim and Objectives of this Research ………….. ………………………………12
1.5 Justification of this Research ……………………………………………………13
10
Chapter 2: LITERATURE REVIEW ………………….………………………………..14
2.1 Potential Health Effects of some Trace Elements…………………….……… 15
2.2 Concentration Levels of Trace Elements in Foods…………………………… 22
2.3 Concentration Levels of Trace Elements in Fish…………………..………… 24
2.4 Concentration Levels of Trace Elements in Tomatoes…………………….… 29
2.5 Surveillance and Regulation……………………….…………………………… 30
2.6 Permissible Limits…………………………………………………………….….. 32
2.7 Analytical Techniques……………….…………………………………………… 36
2.8 X-Ray Fluorescence (XRF) Spectrometry……………………….……………. 36
2.8.1 General Principles of XRF Spectrometry…………………………………….. 38
2.7.2 Types of XRF……………………………………………………………………. 38
Chapter 3: MATERIALS AND METHODS …………………….…………………….. 40
3.1 Materials……………………………………………………………………………40
3.1.1 Samples……………………………………………………………………………40
3.1.1.1 Canned Sardine Fish ………………………………………………………… 40
3.1.1.2 Canned Tomato Pastes………………………………………………………. 43
3.1.2 Sample Composition……………………………………………………………. 48
3.1.3 Sampling Points…………………………………………………………………. 51
3.2 Instruments/Apparatus………………………………………………………….. 56
3.3 Chemicals…………………………………………………………………………. 56
3.4 Analytical Procedure for XRF…………………………………………………… 56
3.4.1 Sample Preparation ……………………………………………………………… 56
3.4.2 Sample Analysis………………………………………………………………… 57
3.4.3 Calibration………………………………………………………………………… 57
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Chapter 4: RESULTS AND DISCUSSION…… ………………………………………58
4.1 Canned Sardine Fish Samples ………………………………………………… 58
4. 2 Canned Tomato Paste Samples……………….………………………………. 67
4.3 The Trace Elements Detected and Health Implications………………………81
4.4 The Results and the Set Objectives……………………………………………. 87
Chapter 5: SUMMARY, CONCLUSION AND RECOMMENDATIONS …….…….. 89
5.1 Summary……………………………………………………………………………89
5.2 Conclusions………………………………………………………………………. 89
5.3 Recommendations……………………………………………………….. ……… 90
REFERENCES ……………………………………………………………………………92
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Project Topics

 

CHAPTER ONE

INTRODUCTION
Natural as well as increasing industrial and human activities worldwide have lead to
transfer of trace elements amongst other components into our environment. These
activities include:
1. Mining, extraction, refining and distribution of mineral substances from their
natural deposits;
2. Agricultural activities like irrigation, application of agro-chemicals and
fertilisers;
3. Industrial and municipal/domestic wastes; and
4. Natural processes like volcanic eruptions, erosions and flood.
These activities and processes could lead to the discharge, distribution and
concentration of these chemicals into especially the water, soil and air environments
and consequently into the food chain [Milacic and Kralj (2003), Tahan et al (1995),
CAOBISCO (1996)].
Some of these elements get accumulated in the body tissues of marine animals (in
water) and crops (which take the elements in from the soil, water and the
atmosphere). Thus an abundance of a certain trace element in the environment may
result in a greatly increased level of that element in plant or animal products
[CAOBISCO (1996)].
Trace elements are present in all foods in varying proportions. The extent of their
presence in two brands of canned sardine fish and four brands of canned tomato
pastes is the focus of this research work.
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1.1 Statement of the Problem
Concerns about the quality and safety of foods we eat has been growing in view of
reports of poisoned or contaminated foodstuffs and presence of toxic trace elements
as well as elevated concentrations of the essential trace elements that may be part
of such foods or added to them.
In fact, food has been identified as the primary means of exposure of the general
population to chemicals, apart from occupational and incidental means. Instances of
poisoning as a result of food consumption include: the 1965 Minamata and Niigata
diseases in Japan which was linked to methyl mercury contaminated fish consumed
there (in Japan) as the causative agent; in Iraq in 1972/73, mercury treated wheat
grains consumed there was reported to have affected 6,500 people and to be
responsible for at least 459 hospital deaths; the Itai-Itai disease with bone damage in
Japan was attributed to the consumption of cadmium contaminated rice [Lindsay
(1981), Hamilton (1979), CAOBISCO (1996)].
Recently, in Nigeria too, there have been reports of ill-health, some of which resulted
in deaths, after consumption of certain foodstuffs (in particular, beans) suspected to
have been treated with pesticides or preserved in containers that may have earlier
been used to package chemicals or poisonous substances.
These developments, amongst several unreported cases, are indeed matters of
serious concern and that is what forms the basis of this research.
1.2 Trace Elements
1.2.1 Definitions
Trace elements have been defined in several ways. Some of these are:
19
(a) Elements that are present at low concentrations (mg/kg or less) in most soils,
plants, and living organisms [He et al (2005), Duffus (2002), Florkin and Stortz
(1971)];
(b) Elements that are present in a given substance in amounts below 50ppm
[CPUT (2005)].
(c) Elements in a sample that have an average concentration of less than100ppm
atoms [en.wikipedia.org (2006)].
Trace elements are most often called trace metals since virtually all of them are
metals. Majority of them are also referred to as heavy metals [He et al (2005)] as in
their standard state, they have a specific gravity (density) of 5gcm-3 or more [Duffus
(2002), CAOBISCO (1996)]. The terms trace elements, trace metals, and heavy
metals have thus been used interchangeably as appropriate in this work.
Trace elements include: aluminium (Al), antimony (Sb), arsenic (As), boron (B),
bromine (Br), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iodine (I),
iron (Fe), lead (Pb), manganese (Mn), mercury (Hg), molybdenum (Mo), nickel (Ni),
nobium (Nb), selenium (Se), silicon (Si), thallium (Tl), tin (Sn), titanium (Ti),
vanadium(V), zinc (Zn) and zirconium (Zr).
1.2.2 Classification
Trace elements can be classified into:
(a) Essential nutritive elements. e.g. Cu, I, Fe, Mn, Mo, Ni, Se and Zn.
(b) Non-nutritive, non-toxic elements. e.g. Al, B, Sn.
(c) Non-nutritive, toxic elements. e.g. Sb, As, Cd, Pb, Hg. [CPUT (2005)].
20
Trace elements have also been classified into: Those essential for higher animals;
those possibly essential; and the non-essential [Underwood (1977)]. An element is
considered essential if its deficiency consistently results in impairment of function
from optimal to sub-optimal [Nicholas and Egan (1975)].
1.2.3 Sources
Trace elements occur in different chemical compounds having varying solubility,
depending upon the chemical and physical environments [Nicholas and Egan
(1975)]. Generally, the abundance of trace elements in foods is related to their
abundance in the environment [CPUT (2005)].
The biogeneous movement of chemical elements in the biogeochemical nutritional
chains can be represented as shown in Figure 1
21
Chemical Elements Plants Foods and Feeds
of the Soil of Plant Origin
Chemical Elements Chemical Elements Human and Animal
in Parent Rock of the Air Organisms
Chemical Elements Animals Food and Feeds
of the Water of Animal Origin
(Intermediary Links)
[Mills (1970)]
Figure 1: Movement of Chemical Elements in the Biogeochemical Nutritional
Chain
22
Contamination of food products with metals can also occur due to pick up of metals
from equipment, processing or packaging materials.
Sources of some specific trace elements that find their way into foods one way or the
other are as in Table 1
23
Table 1: Sources of some Trace Elements
Trace Element Common Sources
As Combustion, agrochemicals, veterinary products.
Cd Zinc smelters, battery industry, pigments, solders, cigarette
smoke, porcelain.
Cr Plating, pigments, tanning, dyeing.
Cu Industrial use, agrochemicals.
Hg Mining, volcanic activity, chloroalkali, electrical industry,
agrochemicals, dentistry, paper industry.
Mn Agrochemicals, paints, red bricks, glass cleaners.
Ni Alloys, plating.
Pb Natural, combustion, paints industries; Solders, accumulators,
anti-rust agents, cigarette smoke, porcelain.
Sb Paints, pigments.
Sn Canning.
Tl Lead smelting, rodenticides.
Zn Plating.
[Jarup (2003), Pickford (1981), NZFSA (2006), CAOBISCO (1996),
health.enotes.com (2007)]
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1.3 Canned Foods
To have all foods available in nearly its complete and natural form retaining virtually
all its essential mineral constituents intact with minimal loses, foods are preserved by
amongst other means, salting, freezing, oiling, smoking, frying and canning. Of all
these, canned foods can remain stable and suitable for consumption for a relatively
longer period of time, thus canning has become one of the most acceptable means
of preserving foods.
Canning can be a safe and an economical way to preserve food quality, despite
possible loses or alteration in the nature of food products during processing. Foods
are canned in glass jars, paper packs, plastics and metal containers with each
requiring some special form of sealing [Kocak et al (2005)].
Canned foods are valuable commodities worldwide [Kocak et al (2005)]. Many foods
begin to lose their essential nutrients and even deteriorate immediately after
harvesting. While some can remain edible and safe for days, weeks or even months,
some begin to deteriorate almost immediately if not consumed or processed and
preserved appropriately.
In addition to trace elements that are part of or accompany the foods from source,
canned foods may take up metals from their container, tin and iron from tin plate, tin
and lead from the solder [CPUT (2005)]. Tin plate used for most metal cans is a light
gauge, steel sheet or strip, coated on both sides with commercially pure tin and has
been used for well over a hundred years as a robust form of food packaging.
Worldwide, about 80,000million cans are used for food packaging [Blunden and
Wallace (2003)].
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Canned foods accumulate more tin when stored for several months and corrosion is
accelerated at temperatures of about 40oC [Joint FAO/WHO CODEX Committee
(2004)].
In this study, two types of foods canned in tin plates: one of animal origin (sardine
fish – two brands) and the other of plant origin (tomato paste – four brands) have
been chosen. They are widely consumed in Nigeria.
1.3.1 Sardines
Sardines are found in temperate waters and can grow up to as long as 12 inches.
They travel in very large “schools” feeding on tiny invertebrates and crustaceans
[www.acornnaturalists.com (2006)]. Sardines used to be abundant just off the coast
of Sardinia, an island in the Mediterranean, hence the name “Sardine”. It is also
known as the Atlantic or Sea Herring, “Pilchards” [www.wholeHealthMd.com (2006)].
Scientifically, sardine is classified as follows:
Kingdom Animalia,
Phylum Chordata,
Class Actinopterygii,
Order Clupeiformes, and
Family Clupeidae.
There are several types of Genus (e.g. Escualosa, Dussumena, Sardinops) and
Species (e.g. Elongata, Elopsoidas, Sagax) [www.answers.com (2006),
en.wikipedia.org (2006)].
The sardine was first canned at the beginning of the 19th century when Napoleon
recognised that there was a need to preserve food, and the Sardine was the first fish
26
to be preserved in oil or tomato sauce. In fact it is one of the world’s first canned
foods [www.wholeHealthMd.com (2006)].
Sardine is packed full of important nutrients such as Omega-3 fatty acids, protein
and calcium. Like other cold water fish, sardines contain the highest amounts of
heart-healthy Omega-3 fatty acids. It is also rich in phosphorous, iron, potassium,
vitamin B6, and niacin. Vitamin B12 and selenium are also available at mg level [Ikem
and Egiebor (2005), www.wholeHealthMd.com (2006)].
Fish and other aquatic life forms are constantly exposed to chemicals in polluted and
contaminated waters. Crustacea, a meal of sardines, accumulate metal ions from the
ambient seawater [CPUT (2005)]. Trace metals may also get into fish from
discharges into water systems like rivers, lakes, seas and oceans.
1.3.2 Tomatoes
Tomato, (derived from tomatl (Nahuatl language) later tomate (spanish)),
Lycopersicum esculentum is an edible, fleshy and usually red fruit (or vegetable) of a
vine native to South America. It is one of the newest plants to be used on a large
scale for human food. It was commonly regarded as poisonous being a member of
Solanaceae (nightshade) family and only within the last century has it become
recognised as a valuable food. Indeed, all parts of the plant but the fruit are toxic
[www.answers.com (2006)]. Numerous varieties (ranging from the small cherry
tomato, globe, plum, to the large beefsteak tomato) in various sizes, shape and
colour are cultivated worldwide.
Technically, tomato is a fruit, but commonly considered a vegetable because of its
uses [www.answers.com (2006)].
27
The tomato is classified as follows:
Kingdom Plantae,
Subkingdom Tracheobionta;
Division Magnoliophyta;
Class Magnoliopsida;
Subclass Asteridae;
Order Solanales;
Family Solanaceae;
Genus Solanum;
Species S. Lycopersicum [www.answers.com (2006)].
Canned tomatoes are available in various forms including [www.answers.com
(2006)]:
1. Canned tomato paste – consists of tomatoes that have been cooked for several
hours, strained and reduced to a deep red, richly flavoured concentrate. E.g.
De Rica Tomato Paste.
2. Canned tomato puree – consists of tomatoes that have been cooked briefly and
strained, resulting in a thick liquid. E.g. Heinz Tomato Puree;
3. Tomato sauce – is a slightly thinner tomato puree, often with seasonings and
other flavourings added so that it is ready to use in various dishes or as a base for
other sauces. E.g. Heinz Tomato Sauce.
The first to commercially can tomatoes was Harrison Woodhull Crosby in
Jamesburg, New Jersey [www.answers.com (2006)].
Tomatoes are rich in vitamin C and contain appreciable amounts of vitamins A and
B, potassium, iron and phosphorous. A medium sized tomato has about as much
28
fibre as a slice of whole-wheat bread and only about 35calories. From its seed,
tomato-seed oil and tomatine (an antibiotic) can be extracted [www.answers.com
(2006)]. Tomato consumption is believed to benefit the heart. Lycopene, one of
nature’s most powerful antioxidant present in tomatoes has been found to be
beneficial in preventing prostate cancer [www.answers.com (2006)].
1.4 Aim and Objectives of this Research
The primary aim of this research is to determine the concentration levels of trace
elements in some canned foods to achieve the following objectives with reference to
canned sardine fish and canned tomato paste samples:
1. To assess the health significance associated with the consumption of a particular
trace element in these foods;
2. To indicate the possible presence of potentially toxic substances in these
samples;
3. To show whether or not the restrictions placed on the use of toxic substances as
additives in the production and/or processing of these foods are being met in
practice;
4. To assess whether there is the need to introduce new legislations or to revise
existing ones as they affect these foods;
5. To indicate the level of safety of these canned foods.
To achieve these objectives, the samples would be analysed using X-Ray
Fluorescence Spectrometry (XRF). It is available at the Centre for Energy Research
and Training/Ahmadu Bello University (CERT/ABU), Zaria.
29
1.5 Justification of this Research
Foods pick up trace elements from either the environment during production or from
processes of handling and preservation such as canning [Pickford (1981)]. Some
trace elements such as mercury, lead, arsenic and cadmium are harmful even at low
concentrations and can cause damage to the basic human systems (cardiovascular,
renal, gastrointestinal, nervous, etc), while others such as copper, iron, zinc and
manganese which are regarded as essential do produce toxic effects at very high
concentration levels [Tuzen (2003), Cid et al (2001), Pickford (1981), CAOBISCO
(1996)] more than what the body requires for normal functioning of its systems.
The concentration levels of trace elements in foods and the amount of food
consumed determines the level of intake of such elements into our body systems
[Ikem and Egiebor (2005)]. Some of the trace elements, especially the toxic ones are
usually persistent and not readily biodegradable [USFDA (2008)].
Therefore, there is the need for continuous study of foods to obtain information on
the concentration levels of all the trace elements in them for the assessment of the
safety of such foods and the associated risks to human health [Llobet et al (2003)]
when consumed.
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