CHAPTER   ONE

1.0 INTRODUCTION

1.1 BACKGROUND

Vegetable oils are plant oils extracted from oil bearing seeds/fruits of plants, and the most common ones include soybean, sunflower, peanut, rapeseed (canola oil), sesame, and safflower oils (Nzikou et al., 2010). They contain 98% triglyceride (triacylglycerol), which is an ester made up of glycerol and different kinds of fatty acids in varying proportion. Vegetable oils, also contain minor components (2%) such as phosphatides, sterols, fat soluble vitamins, tocopherols, pigments, waxes, and free fatty acids (O’brien, 2018). Vegetable oils are widely used in cooking, food processing, pharmaceuticals, and chemical industries. Nutritionally, they are major sources of essential fatty acids, but also carriers of fat-soluble vitamins like as A, D, E, and K (Koski et al., 2002).

Vegetable oils contain fatty acids, which are important components of human body, having biological, structural, and functional roles. Besides their roles as source of energy, they act as main constitute of cellular membranes in this case as part of membrane phospholipids, they assure the fluidity, flexibility and permeability of the membranes (Tiuca, 2017).

Fatty acids such as Omega-3 and Omega-6 are also known as polyunsaturated fatty acids (PUFA) plays important biological roles in the body, which includes anti-inflammatory properties, reducing oxidative stress, neuroprotection and cardiovascular protection (orosavova, 2015).

The composition of fatty acid in vegetable oils may vary depending on factors such as plant genotype, geographical location, environmental conditions, and agricultural practices (Maxia et al., 2009; Gecgel et al., 2007; Bansal et al., 1993; Alizadeh, 2010). Fatty acid composition of vegetable oils is formed by a mixture of saturated and unsaturated fatty acids, and each vegetable oil has specific fatty acid distribution depending on their plant source (Orosavova, 2015). Vegetable oils have a high percentage of unsaturated fatty acids such as Oleic and Linoleic acids in the triacylglycerol. Hwang, (2005) reported that fatty acid composition in sesame seed oil has 80% unsaturated fatty acid consisting of oleic (35.9-42.3%) and Linoleic (41.5-47.9%) acids and less than saturated fatty acid 20%. Fatty acid composition of peanut oils from Uganda has been reported as 39.71-55.89% Oleic acid, 20.21-35.59% linoleic acid and 11.91-17.16% Palmitic acid (Musalima, Ogwok, & Mugampoza, 2019).

Akkaya,(2018) reported that sunflower oil contains approximately 15% saturated and 85% unsaturated fatty acids consisting of 14-43% Oleic acid and 44-75% Linoleic acid.

Fatty acid composition also determines chemical stability, and hence quality of the vegetable oils. It has been reported that polyunsaturated fatty acid in vegetable oils though physiologically important in human nutrition, are the most chemically unstable or more susceptible to oxidative degradation (Rajko et al., 2010). Oxidation of fatty acids may lead to loss of nutritional value and alteration of sensory properties like aroma, flavor, and colour of vegetable oils during processing and storage.

Besides chemical stability, other chemical parameters that affect quality of oils include peroxide value, acid value, iodine value, and saponification value. Physical parameters like smoke point, moisture content, viscosity, refractive index, density, colour also affect quality and purity of vegetable oils (Mohammed and Alli, 2015).

Ansari et al (2009) reported that vegetable oils contain Heavy metals such as cooper, zinc, iron, manganese and Nickel.

The sources of heavy metals contamination in vegetable oils come from soil as natural metal sources, manufacturing and packaging process and environmental pollution (Mendil et al, 2009, Zeiner et al, (2005).

Muhammad et al, (2018) reported the levels of cadmium (Cd), lead (Pb), Iron (Fe) copper (Cu), Zinc (Zn), Manganese (Mn), and Arsenic (As) in vegetable oils as 0.11, 0.04, 0.23, 0.02, 0.16, and 0.12mg/kg respectively.

It is well known that Heavy metals have adverse effects on nutritional value, toxicity and oxidative stability of oils, therefore it is critical to determine the concentration of heavy metals in various oils (Zhu et al, 2011).

Heavy metal toxicity can have several health effects in the body. The heavy metals can damage and alter the functioning of organs such as brains, kidney, lungs, liver and blood (Unak et al., 2007).

Heavy metal toxicity can either be acute or chronic. Long term exposure of body to heavy metals can progressively lead to muscular, physical, and neurological degenerative processes.

Toxicity due to lead (Pb) exposure is called lead poisoning, and is mostly related to gastrointestinal tract and central nervous system in children and adults  (Jaishanka, Anbalagan, Mathew, & Beergowda, 2014).

Long term exposure to cadmium leads to its deposition in bones and lungs, hence causing bone and lung damage (Bernard, 2008).

Iron (Fe) toxicity is related to gastro-intestinal effects such as vomiting, diarrhea, and increased risk of cancer.

The aim of this study was to analyze fatty acids, heavy metal concentration, and characterization of oils from selected oil seeds grown in west Nile sub region Uganda.

1.2 PROBLEM STATEMENT

Fatty acid composition of vegetable oils may differ with changing environmental growth conditions and plant location. It is likely that vegetable oils from different localities have different fatty acid composition, and hence different qualities. The fatty acid profile of the vegetable oils are known but the quantities of individual fatty acids in the vegetable oils may differ due to environmental conditions.

Therefore, there is need to establish and update the quantities of individual fatty acid of vegetable seed oils obtained from west Nile.

Vegetable oils may also contain substantial amounts of environmental contaminants such as heavy metals (Mendil et al, 2009). Artificial fertilizers and pesticide are known to be potential sources of heavy metal contamination in soils where they are applied (He, 2005). Heavy metals enhance oxidation of fatty acids to esters, hence affecting the nutritional value and properties of vegetable oil.

In West Nile, there is extensive use of fertilizers such as super triple phosphate, diammonium phosphate and pesticides in commercial farming, therefore crops grown are at a risk of being contaminated with heavy metals. Hence there is need to determine the concentration of the heavy metals, fatty acid composition and characteristics of oils from oil seeds grown in West Nile region.

1.3 GENERAL OBJECTIVE

To analyze fatty acids, heavy metal concentration, and characteristics of selected oil seeds grown in west Nile, Uganda.

1.3.1 Specific Objectives

1. To analyze the physicochemical properties in the sunflower (helianthus annus), sesame (sesamum indicum) and peanut (Arachis Hypogaea) oils from different locations in West Nile region.
2. To analyze fatty acid content and composition of sunflower, sesame, and peanut oils from different locations in West Nile region.
3. To analyze the concentration of cadmium (Cd), zinc (Zn), iron (Fe), and lead (Pb) in the selected vegetable oil sources from different locations in West Nile region.

1.4 SCOPE OF STUDY

The study focused on the determination of fatty acids, concentration of cadmium (Cd), lead (Pb), iron (Fe), zinc (Zn), and physicochemical properties of selected vegetable oils sources namely, peanut, sesame, and sunflower seed oils purchased from Arua, Yumbe, Nebbi, and Zombo districts in West Nile sub region. The study was carried out from August 2017 to August 2018.

1.5 HYPOTHESIS

Hypothesis (1): there is no significant variation in the physico-chemical characteristics of the vegetable seed oils produced in west Nile region.

Hypothesis (2): There is no significant variation in the fatty acid composition of vegetable oils from seeds produced in different localities in West Nile sub region.

Hypothesis (3): There is no significant heavy metal contamination of vegetable oils from seeds produced in West Nile sub region.

1.6 SIGNIFICANCE OF THE STUDY

Vegetable oils are sources of important fatty acids, embracing all groups of fatty acids.

The findings of this study will help consumers to compare quality of vegetable oil both locally produced and imported.

This study will also aid government and policy makers to develop safety regulation concerning production, refining and consumption of vegetable oils and also data from this study will help researchers get information on fatty acid composition of oils from west Nile region.

Data from this study will help in understanding contamination of vegetable oils by heavy metals and how heavy metals may also accelerate the process of rancidification of oil. Heavy metals are considered as serious inorganic pollutants because of their toxic effects to life when it enters the body through inhalation and ingestion.