FATTY ACIDS, HEAVY METAL CONCENTRATION, AND CHARACTERISTICS OF SELECTED OIL SEEDS GROWN IN WEST NILE, UGANDA
ABSTRACT (Rephrased)
This study examined vegetable oils extracted from three oilseed types—sunflower (Helianthus annuus), sesame (Sesamum indicum), and peanut (Arachis hypogaea)—cultivated in the West Nile sub-region of Uganda. The analysis focused on fatty acid composition, heavy metal content (cadmium, zinc, iron, and lead), and physicochemical properties of the oils. Standard analytical techniques including GC/MS, AAS, and AOAC methods were employed.
The results indicated the presence of key fatty acids such as oleic, linoleic, palmitic, stearic, behenic, lignoceric, and linolenic acids in all oil samples. Major fatty acids ranged between 44.06–44.12% for oleic acid, 30.29–31.51% for linoleic acid, and 10.93–13.07% for palmitic acid. These findings confirm that the oils are predominantly unsaturated and fall within the mid-oleic acid category. Additionally, the ratio of polyunsaturated to saturated fatty acids exceeded the FAO recommended minimum of 1.
Heavy metal analysis revealed the presence of iron and lead in all samples, with concentrations ranging from 2.330–14.982 mg/kg for iron and 1.944–2.126 mg/kg for lead. The highest levels of lead and iron were detected in sunflower and sesame oils, respectively. Cadmium and zinc were not detected. Notably, the detected levels of lead and iron exceeded permissible limits (0.1 mg/kg for lead and 1.5 mg/kg for iron). Elevated iron levels may accelerate oxidation, thereby reducing oil quality, while lead poses significant health risks even at low concentrations.
Physicochemical analysis showed acceptable quality parameters, including density, viscosity, iodine value, peroxide value, acid value, and saponification value. Peroxide values ranged from 1.42 to 9.25 meq/kg, while iodine values varied between 79.64 and 126.59 gI₂/100g.
Keywords: Fatty acids, heavy metals, vegetable oils, oil characteristics
CHAPTER ONE
1.0 INTRODUCTION (Rephrased)
1.1 Background
Vegetable oils are derived from oil-bearing seeds and fruits, including soybean, sunflower, peanut, rapeseed (canola), sesame, and safflower. These oils primarily consist of triglycerides (approximately 98%), which are esters formed from glycerol and various fatty acids. The remaining 2% comprises minor components such as phospholipids, sterols, fat-soluble vitamins, tocopherols, pigments, waxes, and free fatty acids.
Vegetable oils are widely utilized in cooking, food processing, pharmaceuticals, and industrial applications. Nutritionally, they serve as major sources of essential fatty acids and act as carriers of fat-soluble vitamins such as A, D, E, and K. Fatty acids play critical biological, structural, and functional roles in the human body, including forming cell membranes and maintaining their fluidity and permeability.
Polyunsaturated fatty acids (PUFAs), such as Omega-3 and Omega-6, contribute to important physiological functions including anti-inflammatory effects, reduction of oxidative stress, neuroprotection, and cardiovascular health. The composition of fatty acids in vegetable oils varies depending on factors such as plant genetics, geographical location, environmental conditions, and agricultural practices.
Typically, vegetable oils contain a mixture of saturated and unsaturated fatty acids, with unsaturated fatty acids (especially oleic and linoleic acids) dominating. However, higher levels of polyunsaturated fatty acids, while beneficial nutritionally, are more susceptible to oxidative degradation, which can reduce oil quality and alter sensory properties such as taste, aroma, and color.
Oil quality is also influenced by chemical parameters such as peroxide value, acid value, iodine value, and saponification value, as well as physical properties like viscosity, density, moisture content, refractive index, and smoke point.
Vegetable oils may also contain heavy metals such as copper, zinc, iron, manganese, and nickel. These contaminants can originate from soil, environmental pollution, or processing and packaging methods. Heavy metals negatively affect oil quality, nutritional value, and oxidative stability, and may pose serious health risks.
Exposure to heavy metals can lead to organ damage, including effects on the brain, liver, kidneys, and lungs. For example, lead exposure can cause neurological and gastrointestinal disorders, cadmium can damage bones and lungs, and excessive iron intake may lead to gastrointestinal issues and increased cancer risk.
This study therefore aimed to evaluate fatty acid composition, heavy metal concentration, and physicochemical characteristics of oils extracted from selected oil seeds grown in the West Nile sub-region of Uganda.
1.2 Problem Statement (Rephrased)
The fatty acid composition of vegetable oils can vary significantly due to environmental conditions and geographical differences. Although general fatty acid profiles are known, the specific quantities of individual fatty acids in oils from different regions may differ, affecting oil quality.
Additionally, vegetable oils may be contaminated with heavy metals originating from environmental sources such as fertilizers, pesticides, and soil composition. In the West Nile region, the widespread use of agricultural chemicals increases the risk of contamination.
Therefore, there is a need to assess and update data on fatty acid composition, heavy metal concentration, and quality characteristics of vegetable oils produced in this region.
1.3 General Objective (Rephrased)
To evaluate the fatty acid composition, heavy metal concentration, and physicochemical characteristics of selected oil seeds grown in the West Nile region of Uganda.
1.3.1 Specific Objectives (Rephrased)
- To determine the physicochemical properties of sunflower, sesame, and peanut oils from different locations in the West Nile region.
- To analyze the fatty acid composition of these oils.
- To determine the concentrations of cadmium, zinc, iron, and lead in the selected oils.
1.4 Scope of the Study (Rephrased)
The study focused on analyzing fatty acids, heavy metal concentrations (cadmium, lead, iron, and zinc), and physicochemical properties of peanut, sesame, and sunflower oils obtained from Arua, Yumbe, Nebbi, and Zombo districts in the West Nile sub-region. The study period spanned from August 2017 to August 2018.
1.5 Hypotheses (Rephrased)
- There is no significant variation in the physicochemical properties of vegetable oils produced in the West Nile region.
- There is no significant variation in fatty acid composition across oils from different localities in the region.
- Vegetable oils produced in the region are not significantly contaminated with heavy metals.
1.6 Significance of the Study (Rephrased)
This study provides valuable insights into the quality and safety of locally produced vegetable oils. It enables consumers to compare local and imported oils, supports policymakers in developing safety regulations, and contributes to scientific knowledge on fatty acid composition and heavy metal contamination.
Additionally, the findings help in understanding how heavy metals influence oil degradation and potential health risks associated with contaminated oils.
