SOURCE:

Faculty: Biosences
Department: Botany

CONTRIBUTORS:

Anukwuorji, C. A.
Okigbo, R. N.
Amadi, J. E.

ABSTRACT:

ABSTRACT
Mycotoxins and heavy metals contaminants are major threats associated with food materials sold in open markets across the globe. This appalling situation is made worse in the tropics where the warm and humid climate is stable for microbial proliferation. This research work aimed at assessing the quality of cotyledons of Citrullus colocynthis and Irvingia wombolu as well as cassava chips sold in open markets in South-Eastern Nigeria and to determine the effects of some plant extracts in controlling mycotoxigenic fungi. A pre-tested questionnaire on the post-harvest handling practices of Citrullus colocynthis, Irvingia wombolu and cassava chips was used to collect data from food handlers across all the five Eastern States of Nigeria (Enugu, Abia, Anambra, Ebonyi and Imo). Simple random sampling technique was used to collect samples of Citrullus colocynthis, Irvingia wombolu and cassava chips from storage structures in three waves (Wet season, Harmattan and Dry season) between February, 2015 and March, 2016 from three senatorial zones in each of the states in south eastern Nigeria. The food materials were analyzed for aflatoxins (AFB1, AFB2, AFG1 and AFG2) and metals. Thin Layer Chromatographic technique was used for the analysis of Aflatoxins. Wet digestion method was used for the digestion of food materials; these digested food materials were analyzed for lead, copper, zinc and iron using Atomic Adsorption Spectrophotometer. Isolation of fungal pathogens was by serial dilution. Food poisoning technique was used to test for the anti-fungal effects of ethanol and aqueous extracts of Chromolaena odorata and Moringa oleifera on the growth of fungal pathogens of stored Citrullus colocynthis, Irvingia wombolu and cassava chips in vitro. Plant extract concentrations of 2.5%, 5.0%, 7.5% and 10.0% were used for microbial inhibition. Phytochemical screening of the two test plants were carried out using different standard methods. The ethno-study revealed that food handlers across all the states had fairly uniform ways of handling food materials. Foodstuffs in the region are dried mainly by sun drying for just one day and stored for 7-9 months before marketing. These food handlers do not use pesticides and they do not sort out bad ones. The number of fungi isolated varies across the food samples, state of collection and wave of collection, the fungi that were consistently isolated from these food materials were Aspergillus niger, Aspergilus flavus, Rhizopus spp, Fusarium spp, Penicillium spp and Trichoderma spp with mean percentage occurrence of 30.27%, 27.55%, 7.83%, 21.46%, 4.04% and 8.84% respectively across the wave of collection. Most of the fungi were isolated during the Wet season. More fungi were isolated from Citrullus colocynthis and Irvingia wombolu than cassava chips. Aflatoxin was observed in all the food samples, highest in Citrullus colocynthis and lowest in cassava chips; relatively higher concentrations of Aflatoxins were detected in Anambra and Enugu state during Wet season and Harmattan. There was no significant (P<0.05) difference in the concentration of Aflatoxins in Irvingia wombolu across the wave of collection, in cassava chips aflatoxins was detected more during the Harmattan while in Citrullus colocynthis it was observed more during Wet season. AFB1 and AFB2 occur in all the food material across the waves of collection, while only insignificant quantity of AFG1 (0.033ppb) occur in cassava chips across the wave of collection. All the metals tested (in all the food materials) except lead were lower than the maximum permissible level. The value of 0.039 mg/g lead detected in Citrullus colocynthis from Enugu state was significantly higher than other values detected from other food materials and this is more than the NAFDAC permissible level (0.002mg/g). The level of aflatoxins in these food materials across the states were lower than the NAFDAC maximum permissible level (4ppb) but frequent contamination of these food materials and constant consuming of these contaminated foodstuffs may result in bio-acumulation of these toxins in the human system, the presence of AFB1 and AFB2 in their varying concentrations may portend serious health risks for the human and animal population and also has implications for food safety. Inference of this study showed that these foodstuffs are not properly handled by food handlers and they may be medically unsafe for consumption because of their contamination by lead at a level that is higher than the maximum permissible level and also because of the presence of aflatoxigenic and bio-deteriorating fungi. These mycotoxigenic fungi can be controlled by the use of ethanol extracts of M. oleifera at all concentrations (2.5%, 5.0%, 7.5% and 10%) or alternatively aqueous extract of M. oleifera and ethanol extract of C. odorata all at 7.5% and 10% concentration (99.12±0.35). These plant materials have advantages of being readily available and affordable; they are also eco-friendly.