TABLE OF CONTENTS
TITLE PAGE – – – – – – – – i
CERTIFICATION – – – – – – – – ii
DEDICATION – – – – – – – – iii
ACKNOWLEDGEMENTS – – – – – – iv
TABLE OF CONTENTS – – – – – – – v
CHAPTER ONE
1.0 Introduction – – – – – – – – 1
CHAPTER TWO: LITERATURE REVIEW
2.1 Occurrence of Aflatoxins in Food – – – – 5
2.2 Major Sources of Aflatoxin – – – – – 6
2.3 Major Types of Aflatoxins and their Metabolites – – 9
2.4 Impact of Climate on Aflatoxin Production – – – 10
2.5 Detection Methods of Aflatoxins in Food – – – 13
2.6 Aflatoxin Producing Fungi – – – – – 15
CHAPTER THREE
3.0 Chemistry and Biosynthesis of Aflatoxins – – – 17
3.1 Gene Responsible for Aflatoxin – – – – – 18
3.2 Mechanism of Toxicity And Health Effects By Aflatoxin – 20
3.3 Effects of Aflatoxins on Agriculture and Food – – 22
3.4 Effects of Aflatoxin on Mitochonorial DNA – – – 23
3.5 Effects of Aflatoxins on the Immune System – – – 24
3.6 Effect of Aflatoxins on Protein Synthesis – – – 26
3.7 Effect of Aflatoxins on the Central Nervous System – 27
3.8 Effect of Aflatoxins on the Urinary System – – – 28
3.9 Effect of Aflatoxins on Reproductive System – – 30
3.10 Management and Control of Aflatoxin – – – – 32
CHAPTER FOUR: SUMMARY AND CONCLUSION
4.1 Summary – – – – – – – – 34
4.2 Conclusion – – – – – – – – 35
References
Appendix
CHAPTER ONE
1.0 Introduction
Food safety and security are among the major problems in the current climate of increasing population. These are mainly determined by three key aspects viz., (i) enough food availability, (ii) access to safe food and (iii) utilization of the food in terms of quality, nutritional and cultural purposes for a healthy life (FAO, 2015). The failure of any of these aspects leads to food insecurity and malnutrition that further influences human health, in addition to the socio-economic aspect of society. In addition, food and feed contamination by mycotoxins are one of the key factors responsible for creating food insecurity (Udomkun et al., 2017). As per the Food and Agriculture Organization (FAO), one-fourth of the world’s crop is affected by mycotoxins (Pankaj et al., 2018). The three main genera of fungi producing mycotoxins are Aspergillus, Fusarium, and Penicillium (Reddy et al., 2010). Among various type of mycotoxins, aflatoxins (AFs) are highly toxic and are known to contaminate a wide variety of foods such as maize, groundnuts, dried fruits, meat and milk-based products (Iqbal et al., 2015). AFs are produced by Aspergillus species, namely A. flavus, A. nomius and A. parasiticus (Payne and Brown, 1998), in addition to its production by other species of Aspergillus like A. astellatus (Reiter et al., 2009). These fungi usually grow in the warm and humid conditions of tropical and subtropical regions (Battilani et al., 2011). Food processing techniques are not sufficient to eliminate AFs from contaminated food and feed due to their heat resistant nature (Medina et al., 2017).
Aflatoxins are a group of naturally occurring carcinogens that are known to contaminate different human and animal food stuffs. Aflatoxins are poisonous by-products from soil-borne fungus Aspergillus, which is responsible for the decomposition of plant materials (Hasanzadeh and Rexazadel, 2012). The occurrence of aflatoxins foods and food products vary with geographic location, agricultural and agronomic practices. The susceptibility of food product to fungal attack occurs during pre-harvest, transportation, storage, and processing of the foods (Fapohunda, 2007). The problem of aflatoxin contamination of the food products is a common problem in tropical and subtropical regions of the world especially in the developing countries such as the sub-Saharan countries with poor practices and where the environmental conditions of warm temperatures and humidity favors the growth fungi (Fernandez, 2000). The various food products contaminated with aflatoxins include cereals like maize, sorghum, pearl millet, rice and wheat; oilseeds such as groundnut, soybean, sunflower and cotton; spices like chillies, black pepper, coriander, turmeric and zinger; tree nuts such as almonds, pistachio, walnuts and coconut; and milk and milk products (Lopez, 2015). The aflatoxins were initially isolated and identified as the causative agent in Turkey X disease that caused necrosis of the liver in 1960 and over 100,000 turkeys died in England and USA and the death was attributed to the consumption of a mould-contaminated peanut meal (Sudakin, 2003). Very high concentrations of aflatoxins are most often found in nutritive seeds such as maize, nuts and cereal grains in Africa and rice in China and Southeast Asia (Bennett and Klich, 2003).
