1.1 Introduction
Acid value is defined as the amount of potassium hydroxide (KOH) in milligrams required to neutralize the free fatty acids present in one gram of fat or oil (Pearson, 1976). It is an important indicator of oil quality, reflecting the extent of hydrolytic rancidity that occurs when triglycerides in oils break down into free fatty acids and glycerol. High acid values are often associated with deterioration in oil quality, reduced shelf life, undesirable taste, and potential health hazards for consumers (O'Brien, 2004).
Soya bean oil and olive oil are two of the most widely consumed edible oils worldwide. Soya bean oil is prized for its affordability and high polyunsaturated fat content, while olive oil is valued for its nutritional properties and high monounsaturated fat content. On the other hand, despite their benefits, both oils are prone to chemical changes during storage, processing, and handling, which can result in an increase in acid value beyond acceptable limits (Warner, 2010).
This chapter will address the background information that motivated this study, the challenges that prompted it, its aim, and its objectives as a preface to subsequent sections of the study. Additional factors include the study's significance, scope, limitations, research questions, and the definition of technical terms.
1.2 Background of Study
Soya bean oil emerged as a commercially significant vegetable oil in the mid-20th century due to its high yield, affordability, and nutritional benefits. According to O'Brien (2004), large-scale production and processing of soya bean oil increased the need for standardized testing methods, including acid value determination, to ensure consistency and safety for consumers. Similarly, olive oil, with its rich history dating back thousands of years in the Mediterranean region, has long been valued for its monounsaturated fats and health-promoting properties. Studies reported that traditional and modern processing methods, such as cold pressing and refining, can influence the chemical stability of olive oil, making acid value monitoring an essential practice (Warner, 2010).
Research over the decades has asserted that variations in acid value often result from factors such as storage temperature, exposure to light, oxidation, and microbial activity. Choe and Min (2006) stated that oils exposed to high temperatures or prolonged storage exhibit increased free fatty acid content, which negatively impacts both taste and nutritional quality. In addition, regulatory authorities have recognized the importance of acid value in edible oil standards. Pearson (1976) affirmed that established limits for acid values in different oils serve as a guideline for manufacturers and regulators to ensure safe consumption.
Edible oils are a vital component of human diets, providing essential fatty acids, energy, and fat-soluble vitamins. According to O'Brien (2004), the quality of oils is largely determined by chemical parameters such as acid value, peroxide value, and saponification value. The acid value specifically measures the free fatty acids in oils, serving as an indicator of hydrolytic rancidity and deterioration during storage and processing (O'Brien, 2004). It has been reported that commercially available edible oils often exhibit wide variations in acid values due to differences in production methods, handling, and storage conditions (Warner, 2010).
Choe and Min (2006) asserted that oxidative and hydrolytic changes in oils are influenced by environmental factors, refining processes, and packaging, which can lead to increased acidity levels and reduced shelf life. Furthermore, Pearson (1976) stated that monitoring acid value is a standard practice in quality control laboratories to ensure that oils meet established safety and quality standards. On the other hand, studies have affirmed that consumer awareness regarding oil quality is often limited, and many rely solely on brand reputation without verification of chemical properties. Some researchers contend that regulatory frameworks in various regions may not adequately enforce strict quality control, allowing oils with high acid values to circulate in the market undetected (Kamal-Eldin & Appelqvist, 1996).
Given the growing consumption of soya bean and olive oils and their significant roles in human nutrition, it is important to assess their quality regularly. According to Farhoosh et al. (2008), regular monitoring of acid values helps detect early stages of oil deterioration, ensuring consumer safety and prolonging shelf life. This is particularly important for commercially available oils, where storage conditions and handling may vary widely from producers to retail points. This study is set against the backdrop of assessing the acid value levels of commercially available soya bean and olive oils.
1.3 Statement of Problems
Investigation revealed that the quality and safety of edible oils are major concerns in both the food industry and for public health. Soya bean oil and olive oil are widely consumed due to their nutritional benefits and cooking versatility, yet variations in their chemical properties often go unnoticed. One critical parameter in evaluating oil quality is the acid value, which is an indicator of free fatty acids present in the oil. High acid values signify hydrolytic rancidity, which is associated with off-flavors, reduced shelf life, and potential health risks (O'Brien, 2004).
Furthermore, consumer awareness of oil quality is limited, and many rely solely on brand reputation without verification of chemical properties. On the other hand, regulatory frameworks in some regions may not enforce strict testing or labeling, which allows oils with elevated acid values to reach consumers undetected (Warner, 2010). It is against this backdrop that this study seeks to determine the acid value levels of commercially available soya bean oil and olive oil.
1.4 Aim and Objectives of Study
The aim of this study is to evaluate the acid value levels in commercial soya bean and olive oils to determine their quality and adherence to established standards.
The specific objectives of the study are:
- To measure the acid value levels in selected commercial brands of soya bean oil and olive oil in Lagos State, Nigeria.
- To compare the acid values obtained with acceptable international and national standards.
- To identify factors contributing to variations in acid value among different brands.
- To provide recommendations to consumers, producers, and regulatory authorities regarding quality assurance of edible oils.
1.5 Research Questions
Based on the stated objectives, the study seeks to answer the following questions:
- What are the acid value levels of selected commercial brands of soya bean oil and olive oil in Lagos State, Nigeria?
- How do the measured acid values compare with established national and international quality standards?
- What factors contribute to variations in acid value among the different brands of oils?
- What measures can be recommended to ensure the quality and safety of commercially available edible oils?
1.6 Research Hypothesis
In order to pursue the objective of this study, the following generalized statements have been designed to guide and aids in obtaining the result for the experiment to be conducted. For this work, the null hypothesis will be represented with H0 while the alternative hypothesis will be represented with hypothesis H1.
- H0: There is no significant difference between the acid value levels of commercially available soya bean oil and olive oil in Lagos State, Nigeria, and the established quality standards.
- H1: There is a significant difference between the acid value levels of commercially available soya bean oil and olive oil in Lagos State, Nigeria, and the established quality standards.
1.7 Significance of Study
It is believed that at the completion of the study, the findings will inform consumers about the safety and nutritional quality of oils they regularly use. The study will also guide producers and distributors on proper storage, handling, and processing practices to maintain oil quality.
Furthermore, the study will assist regulatory authorities in monitoring compliance with established standards, thereby improving public health outcomes. In addition, producers and distributors will receive guidance on proper handling, processing, and storage to maintain oil quality.
Lastly, the research will contribute to academic knowledge and serve as a reference for future studies in food science and quality control.
1.8 Scope of Study
The study focuses on the determination of acid value levels in commercially available soya bean oil and olive oil within Lagos State, Nigeria. Selected oil brands sold in supermarkets and retail markets in Lagos will be analyzed to evaluate their quality and compliance with national and international standards. The scope includes chemical analysis of free fatty acids in oils using standard laboratory procedures.
1.9 Limitations of the Study
The limitation of this study was that data collection was restricted to commercially available oils in Lagos State, Nigeria, and was influenced by frequent power failures in the laboratory. In addition, delays from respondents and suppliers, as well as financial and time constraints, were challenges that affected the pace of research.
1.10 Definition of Terms
Acid Value:
Acid value is defined as the number of milligrams of potassium hydroxide (KOH) required to neutralize the free fatty acids in one gram of oil (Pearson, 1976). It is an indicator of oil deterioration and hydrolytic rancidity.
Soya Bean Oil:
Soya bean oil is an edible vegetable oil extracted from the seeds of the soybean (Glycine max), widely used for cooking due to its nutritional content and affordability (O'Brien, 2004).
Olive Oil:
Olive oil is a vegetable oil obtained from the fruit of the olive tree (Olea europaea), valued for its high monounsaturated fat content and health benefits (Warner, 2010).
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