ABSTRACT
The study examine mycrotoxins available in food stuff vended in Awka. The findings showed that the various fungi organisms such as Aspergilus spp, fusarium spp, Mucor and Rhizopor are all associated to the foods samples vended in Awka and all this organisms produces aflatoxins of different concentrations. The study indicate that the sample of food stuff gotten from Nwka Amaeyi Market contains high level of fungi infestations as indicated by LSD mean value of 7.1 and those food sample collected from tempsit market and Eke Awka have low level of infestation. Result further, indicated that the level of aflatoxins present in Colocynthis citrullus (Egusi) is of higher concentration as compared to other food samples. The study therefore, recommended that famers should endeavour to use every possible means to reduce the level of fungi infestations on crops in other to reduce the level of spoilage and the rate of aflatoxins. It is also vital that market traders who trade on food stuffs should try to have appropriate storage method to store and preserve food stuff in order to avert fungi infestation.
CHAPTER ONE
1.1 INTRODUCTION
Mycotoxins are derived from the combination of two greek words “mykes” which means fungus and “toxikon” which means poison(Haper douglas, 2008). Thus, mycotoxins are fungal poisons(Bennett, 1987). Mycotoxins are natural products produced by fungi that evoke a toxic response when introduced in low concentration to higher vertebrates and other animals by a natural route (Benette, 1987). Richard(2007) defined mycotoxin as a toxic secondary metabolite produced by organism of the fungi kingdom commonly known as moulds and this toxins are capable of causing diseases and death to humans and other animals.
The term mycotoxin was coined in 1962, in the aftermath of an unusual veterinary crisis near London, England during which approximately 100,000 turkey poults died (Blout, 1961). When the mysterious turkey X disease was linked to a peanut(groundnut) meal which was contaminated with secondary metabolites Aspergillus flavus (Aflatoxins)(Blout, 1961). It then sensitized scientists to the possibility that other occult mould metabolites might be deadly. Soon the mycotoxin rubic was extended to include a number of previously known fungal toxins for example: the ergot alkaloids, some compounds that had originally been isolated as antibiotics, for example patulin and a number of new secondary metabolites revealed in screens targeted at mycotoxins discovery for example ochratoxin (Forgacs, 1962).
Due to the economic loses and the hazards mycotoxins has on human and animals, it is necessary to know more about them because mycotoxin exposure is more likely to occur in parts of the world where poor methods of food handling and storage are common, also where malnutrition is a problem and where few regulations exists to protect exposed population. However, even in developed countries some specific subgroups may be vulnerable to mycotoxin exposure (Barett J, 2000).
Mycotoxin producing mold species are extremely common and they can grow on a wide range of substrates under a wide range of environmental conditions. For Agricultural commodities, the severity of crop contamination tends to vary from year to year based on the weather and other environmental factors. Mycotoxins occur with varying severity in agricultural products all around the world. The estimate usually given is that one quarter of the world’s crop are contaminated to some extent with mycotoxins(Fink Gremmels, 1999). The mycotoxins can enter the food chain in the field during storage or at later points. Mycotoxins problems are exacerbated whenever shipping handling and storage practices are conducive for mold growth. Kuper Goodman(1998) who is a leading figure in the risk assessment field ranks mycotoxin as the most important dietary risk factor higher than synthetic contaminants, plantoxins food additive or pesticides residue.
The economic consequences of mycotoxin contamination are profound crops with large amounts of mycotoxins often have to be destroyed. Alternatively, contaminated crops are sometimes diverted into animal feed. Giving contaminated feeds to susceptible animals can lead to reduced growth rates, illness and death . Moreover, animals consuming mycotoxin contaminated feeds can produce meat and milk that contain toxic residues and biotransformation products thus, aflatoxin in cattle feed can be metabolized by cows into Aflatoxin M1 which is then secreted in milk(Van Egmond, 1989).
It is believed that people who have enough to eat normally avoid foods that are heavily contaminated by molds, so it is known that dietary exposure to acute levels of mycotoxins is rare in developed countries. Nevertheless, many mycotoxins survive processing into flours and meals. When a mold damaged material is processed into food and feed they may not be detectable without special assay equipment. It is important to have policies in place that ensure that such hidden mycotoxins do not pose a significant hazard to human health.
The mycotoxin of most importance in the world are the aflatoxin, Fumoni Sins(FB), Ochratoxin, deoxynivalenol and zearaleone. In this projectI will focus more on Aflatoxins. AFLATOXINS as identified in the early 1960s are secondary metabolites of Asergillus flavus and Aspergillus parasiticus and they contaminate a variety of staple foods particularly maize and groundnut(IARCC, 2002). William et al(2004) have estimated 4.5 billion of the world’s population are exposed to aflatoxin. The aflatoxins occur mostly in tropical regions with high humidity and temperature and they accumulate post-harvest when food commodities are stored under conditions that promote fungal growth. The naturally occurring Aflatoxin are AFB1, AFB2, AFG 1, AFG2 with AFB1 the most abundant toxic and carcinogenic(IARC, 2002).
Arachis hypogea (groundnut) is an important legume crop in many tropical and sub tropical areas of the world and mycotoxin contamination causes economic losses in groundnut processing and export. Aflatoxins are the major mycotoxins that contaminates groundnuts and affects their quality.The Aflatoxin present in groundnut are relatively heat stable and are not eliminated completely by ordinary cooking procedures(Lee et al., 1969). Aspergillus flavus invades groundnut seeds both at pre-harvest growth stages and at post harvest drying and storage producing Aflatoxin B1, B2,G1 and G2(Keenan and Savage, 1994).
Irvingia gabonensis sometimes called bush mango is a dominant tropical forest tree of west and central Africa, which is rated as one of the most domestically consumed wild fruit tree(Ladipo et al.,1995). The department of forest resource management in Ibadan(1986) estimated that annual consumption of Irvingia seed in southern regions of Nigeria ranged from 3.2 to 14.13kg per household. Irvinga kernels are highly susceptible to post harvest spoilage fungi in storage. Studies shows that Irvinga kernels displayed for sale in Nigeria markets are often contaminated with spoilage fungi((Adebayo, 2006; Iyayi, 2010).
Colocynihis citrullus(Egusi) are very important in making Nigeria local soup and constitute a very valuable source of oil and protein(Bankole and Joda, 2004). Melon seed, which is an important oil seed in West Africa has been shown to be prone to fungal and aflatoxin contamination at largely unsafe levels(Bankole, 2006). Also Opadokun(1992) reported high incidence(73%) of aflatoxin in Nigeria melon seed at mean content of 19µgkg. A variety of factors contribute to the susceptibility of melons becoming contaminated during harvest, packing and storage.
This study aims to determine the mycotoxin occurrence and isolate the mycotoxins especially the Aflatoxins that occurs in Ogbono, Egusi and groundnut that are gotten from open markets like Nkwo Amaenyi, Eke-Awka and tempsite comparing their occurrence and determining the frequency of occurrence.
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