Monitoring for aflatoxins and ochratoxins in cereal based infant formula in Nigeria

Aflatoxins and ochratoxins are common contaminants of cereals and cereal – based products. A national survey for aflatoxins and ochratoxins in commercially available cereal based infant formulae was carried out in Nigeria.

Seventy eight (78) samples of cereal based infant formulae were purchased from markets all over the country.  The samples were extracted with (methanol: water 60+40) and cleaned up with Romer multisep column while detection was with liquid chromatograph using fluorescence detector.

The samples were also investigated for Ochratoxins. They were extracted with methanol/water (70:30) while detection was done using the Elisa Agraquant method. The results indicated that more than 50% of cereal based infant formula sold in the Nigerian market contains aflatoxins from 0.1ug/kg to 17.74ug/kg. The samples were also tested for ochratoxins using Elisa method; this also indicated that more than 50% contained ochratoxins at levels between 0.1ug/kg and 13.1ug/kg.

The result of this survey will be integrated with consumption data to develop a dietary exposure for infants in Nigeria.

INTRODUCTION

Nigeria, like many other developing countries is faced with the challenge of providing adequate food supply for its teeming population.  To meet this challenge, policies and programs aimed at boasting Agriculture and Food Production have been actively promoted.  While battling to meet this quantitative demand for the population, it is also faced with the issue of safety in the foods.  It has to contend with the problem of contamination and chemical residues in foods with other attendant social, economic, health and cost problems.

Realizing the central focus that the issue of food safety is attracting globally, Nigeria has taken appropriate and pragmatic steps to ensure food safety and quality for domestic consumption and export. 

Great care has been directed today towards improving and ensuring the quality of analytical data on mycotoxins in agricultural commodities. The data is used for assessing risk from consumer’s exposure (food surveillance), and for food control (regulatory monitoring) or for monitoring standards for trading purposes.

Efforts are being put in place to ensure that mycotoxins are identified correctly and that quantitative data is reliable. The mycotoxins of health concerns, which present unique analytical challenges in term both of obtaining truly representative samples and of understanding analysis at stringently low regulatory limits of control, mostly imposed due to SPS measures for precautionary safety principles are being analysed in NAFDAC – Nigeria from 2003 till date. Analytical methods for aflatoxins and ochratoxins have been validated in – house.

Mycotoxins have been linked to cancer and possible disruption in small children’s growth and immune system development; hence food producers and regulators in most countries have been aggressive in their attempts to keep mycotoxins out of the food supply or at least at barely traceable levels.⁵

Aflatoxins cause cancer in the liver of laboratory animals by damaging the DNA. They have also been linked to cancer in a number of developing countries where some foods that are an important part of the diet can contain high levels of aflatoxins. Deaths of a large number of people have also been reported in Kenya after eating maize that was highly contaminated by aflatoxins.

 Ochratoxin A has been shown to damage and cause cancer of the kidneys in laboratory animals. The consumption of foodstuffs highly contaminated by ochratoxin A has been associated with the development of Balkan Endemic Nephropathy (a specific type of kidney disease) in certain human populations.

The aim of this study is to determine the presence of aflatoxins and ochratoxins cereal based infant food products marketed in Nigeria

To produce information that can be used for assessment of the dietary exposure of infants to aflatoxins and ochratoxins by consumption of infant milk cereal products.

To assess the risk to public health from consumption of mycotoxins, the exposure of consumers to these toxins can be compared to safety guidelines such as Tolerable Daily Intakes (TDIs).


Dietary Exposure Estimates

TDIs set by scientific committees are based on threshold levels identified during toxicological studies, below which the toxins are considered not to cause adverse effects.

A TDI represent an estimate of the amount of a contaminant, expressed on a body weight basis, which can be ingested daily over a lifetime without appreciable health risks.

Dietary exposure to mycotoxins can be estimated for an average consumer and for high level consumers using data derived from National and Nutrition Surveys. These estimates can be compared with tolerable daily or weekly intakes (TDI or PTWI) established by expert committees. In Nigeria these data are not available hence the option of using consumption estimate based on feeding guidelines suggested by infant formula manufacturers. The guideline assumes that all food served is consumed and retained by the child, this may be an overestimate.²  

To assess the risk of Ochratoxin A intake, the provisional Tolerance weekly Intake (PTWI) established by the joint FAO / WHO Expert Committee on Food Additives (JECFA) AT 100ng/kg bw per week (JECFA, 1995), equivalent to a tolerable daily intake of 14ng/kg bw/day was used.


Methodology

Samples were purchased from the open market outlets and shops in the Western, Eastern and Southern part of Nigeria within the shelf life of the products.

Two analytical methods were used:

1. High performance liquid chromatography
   
2. Elisa method

Method overview (Determination of total aflatoxins by HPLC):  Grinding, weighing, addition of extraction solvent (methanol: water 60+40), shaking (60 min.), filtering, immuno affinity column clean up, concentrating, re dissolving, injecting and determination (AOAC 2000)

Elisa method (Determination of ochratoxins): Grinding, weighing, addition of extraction solvent, (methanol: water 70+30), filtering, incubation and determination.


Validation report for total aflatoxins

Analytical results

CONSUMPTION DATA

100gramms /person/day
ESTIMATION OF DIETARY INTAKE BY A CONSUMER WEIGHING 20kg
Total Aflatoxins daily intake = (1.75µg/kg *100g)/20kg = 8.74ng/kg bw/day
Ochratoxin A daily intake = (0.6µg/kg*100g)/20kg = 3ng/kg bw/day

References:

1. P.A. Burdaspal and T.M. Legarda Centro Nacional de Alimentacion (Spanish Agency of Food Safety) 28220 Majadahonda (Madrid) – Spain “Occurrence Of Ochratoxin A In Processed Cereal Based Products Marketed In Spain”
   
   
2. Food Survey Information Sheets on the www : www. food.gov.uk /science/surveillance FSIS 68/04

Authors: B. F. OGUNBANWO: F. A. AYOADE, T. F. IMAFIDON, F. I. FASINA, E. N. NDEN, DENLOYE S.A Mycotoxin Unit, Oshodi Central Laboratories, National Agency for Food and Drug Administration and Control, (NAFDAC) Lagos, Nigeria.