ABSTRACT
This
research was conducted to determine the concentrations of heavy metals and
proximate composition of different cereals (maize, millet and rice).Two
different samples each sold in two different markets (Ogbete and Gariki) in
Enugu, were used for this work, using atomic, absorption spectrophotometer. The
heavy metal screening of the cereal samples showed the presence of arsenic in
the range of 0.456ppm-0.955ppm but was not detected in sample E and f which are
the two different rice I purchased from Ogbete market, then mercury in the
range of 0.024ppm-0.124ppm, lead in the range of 0.554ppm-1.083ppm, cadmium in the range of
0.087ppm-0.565ppm, copper in the range of 0.050ppm-0.245ppm and zinc in the
range of 1.448ppm-66.954ppm which is the highest and is discussed. The result
of proximate composition analysis indicated ash: 1.0%-19.0%, moisture:
8.6%-12.6%, fat: 0.2%-20.0%.
CHAPTER
ONE
INTRODUCTION
1.0 BACKGROUND OF THE STUDY
Cereals are enriched
with niacin, iron, riboflavin and thiamine, and most cereals have abundant
fiber content, especially barley, oat, and wheat. Cereals also have soluble
bran that aid in lowering blood cholesterol level and keeping heart diseases at
bay. Cereals consumption also means an intake of high amounts of protein;
breakfast cereals are often eaten with milk that makes for a protein-rich meal.
For infants, iron-fortified cereals are said to be the premium solid food.
A cereal is any grass
cultivated for the edible components of its grain (botanically, a type of fruit
called a caryopsis), composed of the endosperm, germ, and bran. Cereal grains
are grown in greater quantities and provide more food energy worldwide than any
other type of crop; they are therefore staple crop.
In their natural form
(as in whole grain), they are a rich source of vitamins, minerals,
carbohydrates, fats, oils, and protein. When refined by the removal of the bran
and germ, the remaining endosperm is mostly carbohydrate. In some developing
nations, grains in form of rice, wheat, millet, or maize constitutes a majority
of daily substance. In developed nations, cereal consumption is moderate and
varied but still substantial. The growth of civilizations, or development in
the human diet patterns, the cultivation of cereal grains has played a
significant role. The word ‘cereal’ is derived from ‘ceres’- the name of the
Roman goddess of agriculture and harvest. It is said that almost 12,000 years
ago, ancient farming communities dwelling in the Fertile Crescent area of
southwest Asia cultivated the first cereal grains. The first Neolithic founder
crops that actually initiated the development of Agriculture include einkorn wheat,
emmer wheat and barley. Cereals are the important sources of many essential or
beneficial components to the human diet. For example, the National Diet and
Nutrition Survey of the UK showed that cereal products contributed 29/30% of
the total daily energy intake of adult males/females, 22/21% of the intake of
protein and 39/37% of the intake of non
starch polysaccharides (the major components of dietary fiber, DF) (NDNS,
2011).
Cereals are probably
the greatest source of energy for humans. Providing almost 30% of total
calories in a regular diet, cereals are probably the most widely consumed
caloric food in America. This percentage rises in places like rural Africa,
Asia and India where cereals are reported to supply almost 70 to 80% of energy
requirements (since people in these regions cannot afford to eat other food
product like fruits, vegetables, meat, or milk products. Cereals are
inexpensive and a widely available source of energy; this is probably the prime
reason why people from all budgets prefer cereals as the major energy provider
in their diet. Cereal intake tends to be quite high almost poor income families
as they attain good amount of energy through mineral expenditure.
In cereal, around 95%
of minerals are the sulphates and phosphates of magnesium, potassium and
calcium. A good amount of phosphorous in cereals is present, called phytin. The
phylates present in the cereals considerably reduce the activity of iron
absorption. The unrefined cereals have more phytates as compared to refined cereals. After the cereals germinate, phytates
diminish due to the breakdown of enzymes, and then the iron content is
enhanced. This is the reason why molted flours of cereals are said to have more
nutritional value than raw flour. Zinc, copper and manganese are also present
in cereals in very small quantities. Cereals hardly have and calcium and iron,
but ragi is an exception to this. Amongst cereals, rice is the poorest source
of calcium and iron. Ragi, millets, jowar and bajra have high amounts of minerals
and fiber.
Whole wheat products
reduce the chances of breast cancer. Cereals are rich in phytosterols or plant
based steroids plant estrogen that stimulates hormone estrogen. Phytosterols
binds to estrogen receptors present in the tissues of the breast and blocks
human oestrogen that promotes the growth of breast cancer. many studies have
shown that colon cancers can be avoided by consuming whole wheat products or
any fiber-rich cereals. Phytosterols increase the stool movement through the
intestines, thereby constricting the re-absorption time of the estrogen into
the blood through the colon wall.
Cereals have both
soluble and insoluble fibers like cellulose, pectin, and hemicellulose. These
fibers are present in the bran and pericarp, which often gets demolished while
processing, thus it is advisable to consume whole cereals to cure extreme
constipation troubles. Cereals also effectively improve peristalsis in the
intestine and increase the bulk of the stools, thus keeping your internal
system clean. Ragi is high in cellulose and has excellent laxative properties
that relieve constipation. Brown rice is also helpful for treating this
disorder.
The fiber content in
cereals decreases the speed of glucose secretion from food, thereby maintaining
sugar levels in the blood.
Proteins are present in
every tissue of the cereal grain. the concentrated protein-rich areas are
scutellum, embryo and alleurone layer and moderate amount can be found in the
endosperm, pericarp and testa. The concentration of proteins becomes denser in
the endosperm from the center to the borderline. The cereal protein are of
different types; like albumins, prolamines gliadins, globulins and glutelins.
These type of proteins are called ‘’gluten’’ protein. This gluten has
extraordinary elasticity and mobile properties mainly present in wheat grain,
but also in some other types of cereals. Cereals usually have 6-12% protein but
lack in lysine. The protein content varies in each type of cereals. For
instance, rice contains less protein in comparison to other cereals. In fact,
the protein percentage even varieties with different varieties of the same
cereals. Although less in amount, the quality of rice protein is better than
the protein of other cereals. When you consume cereals with pulses, the protein
quality automatically improves, owing to the mutual supplementation. Pulses
have high lysine content and are deficient in methionine; on the other hand
cereals have an abundance of methionine.
Recent
research suggests that greater consumption of vegetable, whole grain products
and fruits may lower the risk of multimorbidity. If you are suffering from a
deficiency in the vitamin B complex, add whole grain cereal to your diet. Most
of the vitamins of cereals are present in the outer bran, but the refining
process usually reduces the vitamin B content, and thus it is advisable to
consume whole grain cereals. Cereals are usually devoid of either vitamin A or
vitamin C; only maize has small amounts of carotene. The cereal grains are
processed to extract oils that are rich in vitamin E. Rice bran oil has more
concentrated amounts of vitamin E than other oils available on the market.
Cereals grains are rich in enzymes, particularly protease, amylase, lipases and
oxido-reductases. After the seed germinates, amylase actively increases. The
germ encloses the protease enzymes. Cereals are undoubtedly full of nutrition,
but unfortunately, the refining process degrades their quality. The degree of
milling, polishing and refining to some extent decides the nutrition content of
cereals. Some nutrients are lost during food preparation, especially vigorous
washing, soaking and cooking methods, which results in the depletion of the
nutrients on the skin of the grains. Heavy metal of cereals cannot be
underestimated as these foodstuffs are important component of human diet.
However, heavy metal contamination of food items is one of the most important
aspects of food quality assurance (Marsshall, 2004; Radwan and Salama 2006; and
Khan et al., 2008).
Though
heavy metals are naturally present in soil, geology and anthropogenic
activities increase the concentration to a harmful mount (chibuike and obiora,
2014). In many ways living plants can be compared to solar driven pumps which
can extract and concentrate several elements from their environment. From the
soil, all plants have the ability to accumulate heavy metals which are
essential for their growth and development like magnesium, iron, manganese,
zinc, copper, molybdenum and nickel (Langille and Maclean, 1976) certain plant
also have the ability to accumulate heavy metals which have no biological
function. These include cadmium, chromium, silver, selenium, and mercury (Hanna
and Grant, 1962: Baker and Brooks, 1989). it is also well known that the growth
and economic yield of plants is significantly depressed when they are raised on
soils contaminated with heavy metals (Foy et
al., 1978; Lepp, 1981; Woolhouse,1983).
The
prolonged 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 (WHO,1992 and
Jarup, 2003).
1.1 STATEMENT OF PROBLEM
Metals have important
and wide ranging role in biochemistry, being both essential and toxic
(Guengerich 2009). Deficiency of micronutrient in soils and plant is a global
nutritional problem as the major food staples are highly susceptible to such
deficits (Imtiaz et al. 2010) for example,
essentiality of Zn in the diet and its deficiency in humans was recognized in
1963 (Prasad 2012). However among all the environmental stresses, the effect of
the metal accumulation has been considered one of the most disturbing factors
arising in the late 19th and early 20th centuries
(Azevedo et al. 2012) in addition to
their essentiality for plant growth and human nutrition, some micronutrients
may also be toxic to animals, including humans, at high concentrations (Wang et al 2008). For example, Cu or Zn. An
important component of seed quality is its chemical composition, including the
concentration of micronutrients such as Fe, Zn, and Cu (Waters and Sankaran
2011). Clearly, plants are the first step of a metal’s pathway from the soil to
heterotrophic organisms such as animals and humans, so the micronutrient
content in their edible parts makes a major contribution to human intake. Zhao
and McGrath (2009) suggested that micronutrient in humans and environmental
contamination with heavy metals or metalloids are both global and challenging
problems that require concerted efforts from researchers in multiple
disciplines, including plant biology, plant breeding as well as biotechnology,
nutrition and environmental sciences, such as soil fertility and chemistry.
In this review, can we
continue with the intake of cereals? Or is it still possible to provide an
overview of data regarding micronutrients concentration in the grain of some
important cereals published in the last two decades, as well as the prevailing
opinions on their plant-driven entry into the food chain.
1.2 AIM AND OBJECTIVES OF RESEARCH
The aim of this study
is to characterize some cereals for their level of some extracted heavy metal
contamination.
The specific objectives:
·
To check for the level of extracted
heavy metals in the selected cereals
·
To determine the proximate composition
of the cereals
·
To compare the levels of heavy metals in
different selected cereals
1.3 LIMITATIONS OF STUDY
The study is limited to
availability of very dried cereals in the market due to rain because is rainy
season at the time of the research
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