Determination of Heavy Metals and Proximate Analysis in Some Selected Cereals

Determination of Heavy Metals and Proximate Analysis in Some Selected Cereals

Chapter One

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

CHAPTER TWO

LITERATURE REVIEW

COMPOSITION OF CEREALS

In composition, grains are structurally similar as seen; however, they vary in their nutrient composition, containing varying amounts of carbohydrate, fat, protein water, vitamins and minerals.

CARBOHYDRATES

The main nutrient component of cereals grains is carbohydrate which makes up 79-83% of the dry matter of grain.

It exists predominantly as starch, with fiber especially cellulose and hemicelluloses, composing approximately 6% of the grain.

Carbohydrates can be classified according to their molecular size and decree of polymerization, with each group being subdivided according to the number and composition of monosaccharide units. This is classification includes sugars (monosaccharides and disaccharides), oligosaccharides, starch (amylose and amylopectin) and non-starch polysaccharides.

LIPIDS

Lipid (fats and oil) makes up approximately 1-7% of kernel, epending on the grain. For example, wheat rice, corn, rye and barley contain 1-2% lipid, oats contain 4-7%. The lipid is 72-85% unsaturated fatty acids, primarily, oleic acid and linoleum acid.

PROTEINS

Protein composes 7-14% of the grain, depending on the grain. Cereals are low in the amino acids tryptophan and methionine, and although potential breeding may produce cereals higher in the amino acid lysine, it remains the limiting amino acid in cereals.

Grain consumption provides half of the protein consumed worldwide. However, in comparison to food such as milk, meats or eggs, grains do not include all the essential amino acid contained in animal protein.

The protein is of low biological value and therefore, less efficient in supporting body needs. Combining food sources of protein is common in cultures throughout the world. The preparation of traditional dishes combines the lower biological value grain with legumes or nuts and seeds to provide the needed amino acids to yield a complete dietary protein.

For example a combination of beans with rice, or beans with cornbread, tofu and vegetables, or tofu and cashews, chickpeas and sesame seed paste (tahini) known as hummus, peanut butter on whole wheat bread and so forth are combinations creating complete proteins.

VITAMINES

Vitamins present in cereals are predominantly the B vitamins-thiamin (B1), riboflavin (B2) and niacin (B3) which are among water soluble vitamins. These vitamins may be lost in the milling process and so are added back through the process of enrichment.

Whole grain products contain some fat soluble vitamins in the germ.

Vitamin B-1 (thiamine): it is involved in breaking down of carbohydrate since it increases the production of gastric acid, it is nicknamed, the ‘’morale’’ vitamin because drops in b-1 levels can result in depression. Thiamine is also necessary for growth, fertility, lactation.
Vitamin B-2 (riboflavin): it used in eye-formula for its ability to prevent cataract and ward off eye fatigue. Recent studies suggest that 400mg of B-2 vitamin can ward off migraine headaches.
Vitamin B-3 (Niacin, Nicotinic acid, Niacinamide): Niacin’s fame in medicine today is its ability to at high doses lower cholesterol and high triglyceride levels.
Vitamin B-5 (Pantothenic acids): therapeutic uses of this vitamin may include allergies, arthritis and hypoglycaemia.
Vitamin B-6 (pyridoxine): its therapeutic uses include morning sickness, premenstrual syndrome and menopause, edema, birth control pills induced deficiencies and the reduction of homocysteine a toxic amino acid metabolite associated with heart disease.
Vitamin B-12 (cyanocobalamin): many health professionals its therapeutic use is in muscle weakness, nerve degeneration, homoysteine control and anemia.
Folic acid: one of the great revelations of the 90’s was the confirmation that a folic acid deficiency during pregnancy will increase the chances of having a child with spina bifida or anencephaly. Women of child bearing age who consume adequate amounts of folic acid daily (400mg) before conception will reduce their risk of having pregnancy affected by neural tube defects.
PABA (para-Aminobenzoic acid): therapeutic applications include prevention of eczema and loss of skin pigmentation, control of burn pain and topical use in sunscreen.
Choline: therapeutic uses include memory enhancement, liver disorders, lowering of cholesterol, nervous system disorders and hair, nail and skin enhancement.
Inositol: it is used as a lipotropic agent for hair health.
Biotin: therapeutic applications include hair health, eczema and Candida.

CHAPTER THREE

Materials and Method

MATERIALS

The following materials were employed in the study

Equipment/Apparatus

Beaker
Electric blender
Distilled water
High density polyethylene sieve
Whatman No.42 Filter paper
100ml reflux flask
Electronic blender
Heating mantle
Volumetric flask
Conical flask
Platinum crucible
Bunsen burner
Atomic Absorption Spectrophotometer Machine

Chemicals/Reagents

Concentrated Nitric acid (NHO₃)
Concentrated Hydrogen Peroxide ( H₂O₂)
Perchloric Acid (HClO₄)
De-ionized (DI) water and
Sodium hydroxide ( NaOH )
Distilled water
Tetraoxosulphate(VI) Acid ( H₂SO₄)
N-Hexane

METHODS

Collection of samples

A total number of twelve cereals were purchased. Six were purchased from ogbete main market and the other six from garriki market in Enugu state

CHAPTER FOUR

RESULTS AND ANALYSIS

PROXIMATE COMPOSITION

The nutritional analysis of proximate composition of dry cereals of corn, millet and rice.

CHAPTER FIVE

DISCUSS AND CONCLUSION

Discussion

The rice samples contained high quantities of carbohydrates ranging from 55.00% to 78.80%. Although these values are higher than the values obtained by Eggum (1982), they are a bit lower than the values (75.37 to 76.37%) reported by Edeogu et al. (2007) who analysed the proximate compositions of staple food crops in Ebonyi State. Sample H variety had the lowest carbohydrate content. This low carbohydrate content may be attributed to its high crude fibre content which also affects the digestion activities (Online USA Rice Federation, 2002) and other environmental factors. The high percentage carbohydrate contents of the rice varieties show that rice is a good source of energy. The ash content of a food sample gives an idea of the mineral elements present in the food sample. Among the five rice varieties, sample G rice had the highest protein content (10.20%). This is in agreement with the findings of Ebuehi and Oyewole (2007) who analyzed the effect of cooking and soaking on physical characteristics, nutrient composition and sensory evaluation of indigenous and foreign rice varieties in Nigeria. The percentage fiber contents among the five rice samples were in the range of 0.5 to 8.5%. Although this range is a bit lowerthan obtained by Edeogu et al. (2007), it is similar to the mean value obtained by Sotelo et al. (1990). Milling of rice generally decreases the fibre contents of rice. Sotelo et al. (1990) who analyzed the chemical compositions of different fractions of 12 Mexican varieties of rice obtained during milling. Sample A and B variety contained the highest percentage moisture content while sample K variety contained the lowest percentage moisture content. The high percentage moisture content may be attributed to low drying temperature (Xheng and Lan, 2006) and prolonged parboiling. Such high percentage moisture content affects the milling characteristics and the taste of cooked rice (Xheng and Lan, 2006). Ebuehi and Oyewole (2007) reported that the moisture content of rice also affects its storage. It follows that sample K variety may have a longer shelf life compared to the other samples due to the lower moisture content. The values for percentage crude protein content are in the range of 0.2 to 10.20%. This range is lower than the range obtained by Edeogu et al. (2007) who analyzed the proximate composition of cereals in Ebonyi Sate. This may be attributed to prolonged parboiling which lowers the protein content of the samples and some other environmental and edaphic factors. However, the range is comparable with the range obtained by Ibukun (2008). The percentage fat content of the rice is in the range of 0.2 to 20.0%. The results of this study are in agreement with earlier results reported by Willis et al. (1982) and Juliano (1985) who also gave the fat range 0.9 to 19.97% in different milling fractions. However, this range is lower than the range obtained by Edeogu et al. (2007). This difference may be attributed to the degree of milling.

While their heavy metal detection varies at minute quantities, this could be as a result of environmental factors, expect zinc that recorded higher value in all the samples

CONCLUSION

The result of this study can be exploited by cereal consumers in their choices regarding mineral and proximate compositions. All samples were observed to have good percentage values. Therefore, all the samples should get more attentions in terms of proximate and mineral compositions. While their heavy metal detection varies at minute quantities, this could be as a result of environmental factors, expect zinc that recorded higher value in all the samples

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