Reduction Of Aflatoxin Contamination Of Maize Meal Foods In The North-Kivu Province Of Democratic Republic Of Congo By Nixtamalization

Abstract

The Democratic Republic of Congo relies on maize as one of the staples food for human, for animal feed and for industrial uses. However, it has been shown that maize and maize products are good substrates for growth of molds and production of aflatoxin. Levels higher than the tolerance of 10ppb of aflatoxin have been reported in maize consumed in DRC. This study was therefore intended to asses the level of aflatoxin-contamination of maize and maize products consumed in the three main cities (Butembo, Beni and Goma) of the North-Kivu Province of DRC, in which maize is increasingly becoming the main staple food consumed as ugali. The study also evaluated the effect of lime-cooking of ugali on its levels of aflatoxin as eaten with the aim to reduce to the tolerance of 10ppb for total aflatoxin. The acceptability of ugali cooked with lime was evaluated using sensory testing procedures. The ugali analyzed consisted of that from the grilled and from the non-grilled maize meal. The study started with a survey of households to establish the type of ugali consumed (from maize meal, cassava flour or mixtures with cassava flour) and the method for preparation of ugali for consumption. For the survey, a sample of 384 households was used. The sample was partitioned between the three Cities proportionate to their populations. The sample size was calculated using Cochran formula. For aflatoxin assessment, a total of 30 samples of 2kg each of maize kernels were collected, 10 samples from each of the three Cities, in each city, from five (5) principal open air markets. The samples of maize kernels from Butembo consisted of five grilled and five non-grilled. Each of the 2Kg of maize kernels was separately milled in a local mill and then, from each, 1kg of the meal was packaged in Kraft Paper bags. The maize meal samples were then packaged in Kraft paper bags and taken to the Laboratories of the Department of Food Science, Nutrition and Technology, University of Nairobi and stored in a cool dry place, away from direct sunlight to xiv await further processing and analyses. The ugali cooking simulated the method practiced in households and the same method was applied for both grilled and non-grilled Ugali. The data from the survey was collected using the structured questionnaire. Aflatoxin was analyzed as total aflatoxin using ELISA Kit method according to the manufacturer instructions. Moisture was determined by drying about 5g samples accurately weighed in a porcelain crucible in a thermostatically controlled air oven at 105oC to constant weight according to the AOCC method. Sensory evaluation was done using a seven-point hedonic rating scale (1 = Dislike very much and 7 = Like very much). Data showing the aflatoxin content for maize meal and nixtamalized ugali, moisture content, Calcium content and sensory evaluation were subjected to one way ANOVA using Genstat® Discovery 13thEdition at 95% confidence interval (P≤ 0.05). Results from the survey showed that the methods of cooking ugali and the types of ugali consumed in households differ from one city to another. Results showed that the mean levels of aflatoxin in all the maize meals collected in the three cities are above 10ppb, the tolerance level of aflatoxin in the maize meals for human consumption. The means ranged between 18.34 and 20.98 ppb, the highest mean was for Goma city. The moisture contents of many of the meal samples, and obviously also the maize samples that were milled, were above the optimum for storage except for the grilled samples. That implies that the toxin producing molds would continue to grow and produce the toxin during storage. Cooking of ugali using the conventional method did not reduce the aflatoxin in the food to below the tolerance. However, cooking the ugali with addition of 1%-3% calcium hydroxide (lime) reduced the levels of aflatoxin to below the tolerance of 10ppb for total aflatoxin. This ugali was acceptable to the consumer as indicated by the results of acceptability testing by a xv laboratory panel. Cooking with lime also increased the nutritional value of the ugali with respect to calcium. The study concluded that the maize and maize meals consumed in the three major cities of North Kivu Province are contaminated with aflatoxin at levels way above the 10ppb for total aflatoxin, higher levels occurring in Goma than in the other two Cities. The moisture content of most maize samples that were milled was also higher that the optimum for storage to prevent growth of the toxin producing molds. Cooking of the ugali with addition of 1% calcium hydroxide on the basis of the maize meal reduced the aflatoxin levels of the ugali to below the tolerance, and the ugali still remained acceptable to the consumer.