Distribution of fungi and their toxic metabolites in melon and sesame seeds marketed in two major producing states in Nigeria

Adetoun O Esan,Rudolf Krska,Chibundu N Ezekiel,Stephen O Fapohunda,Michael Sulyok

doi:10.1007/s12550-020-00400-0

Abstract

In this study, melon (n = 60) and sesame (n = 60) seeds purchased from markets within Benue and Nasarawa states, respectively, in Nigeria, during two seasons (dry and wet), were analysed for fungal and mycotoxin contamination in order to determine the safety of these foods for human consumption. Molecular analysis revealed the following seven fungal taxonomic groups in the foods: Aspergillus section Candidi, Aspergillus section Flavi, Aspergillus section Nigri, Cladosporium, Fusarium fujikuroi species group, Penicillium, and Pleosporales/Didymellaceae. A total of 78 microbial metabolites, including several mycotoxins, occurred in the foods. The most frequent mycotoxins in melon and sesame were aflatoxin B1 (occurrence: 76%) and alternariol monomethyl ether (occurrence: 59%), respectively. However, higher mean total aflatoxin levels occurred in sesame (17 μg kg−1) than in melon (11 μg kg−1). About 28 and 5% of melon and sesame, respectively, exceeded the 4 μg kg−1 total aflatoxin limit for oilseeds intended for direct human consumption in the European Union. Additionally, fumonisin B1 and moniliformin occurred only in sesame, whilst ochratoxins A and B occurred only in melon; ochratoxin B being reported for the first time in this food. Our data indicated seasonal variations in the fungal and mycotoxin contamination levels in both foods.

Highlights

Mycotoxin contamination of food resulting from fungal invasion and subsequent biosynthesis of the toxic secondary metabolites is a global challenge, posing a huge hurdle to availability of safe food in regions where food safety systems are poorly developed (Ezekiel et al.Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.2019)
One major limiting factor to the export of both crops, especially melon seeds, to the European Union territory is Mycotoxin Res contamination with mycotoxins beyond the regulatory limits of 2 and 4 μg kg−1 for aflatoxin B1 and total aflatoxins, respectively, set by the European Commission for oilseeds intended for direct human consumption (European Commission 2010; RASFF 2019)
A seasonal mycotoxin surveillance study was conducted within each state ranked as the highest producer of melon and sesame seeds in Nigeria

Summary

Introduction

Melon (Colocynthis citrullus L.) and sesame (Sesamum indicum) seeds are widely grown in West and Central African countries, and Nigeria ranks first and fifth, respectively, on the global list of highest producing nations. Nigeria contributed 568,940 and 450,000 t to the global production of 925,422 and 5,631,443 t of melon and sesame seeds, respectively, in 2016 (FAOSTAT 2019a). The export quantities of melon and sesame seeds from Nigeria in 2016 were 5 and 172,839 t, respectively (FAOSTAT 2019b). One major limiting factor to the export of both crops, especially melon seeds, to the European Union territory (the major market for several African countries) is Mycotoxin Res contamination with mycotoxins ( aflatoxins) beyond the regulatory limits of 2 and 4 μg kg−1 for aflatoxin B1 and total aflatoxins, respectively, set by the European Commission for oilseeds intended for direct human consumption (European Commission 2010; RASFF 2019). There is a continuous need for monitoring and tracking compliant and violative agricultural commodity shipments at the local market before they get to the international market

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Results