Nixtamalization Of A Supplementary Porridge For Children: Effect On Physico-Chemical Characteristics, Nutrient Intake, Aflatoxin Contents And Aflatoxin Exposure

Abstract

Prevalence of Protein Energy Malnutrition (PEM) in under five year old children in Malawi is one of the highest in the world at 30% underweight, 49% stunting and 70% wasting. This prompted the development of a maize-soybean flour blend for porridge preparation called Likuni Phala to help alleviate the problem. The product is manufactured by local industries, some of whom distribute for retail to the general public and some distribute to rehabilitation institutions involved in child feeding and rehabilitation. Maize is a staple food for Malawi but consumption is challenged by the high levels of aflatoxin. Because of this, it is expected that there will be carryover aflatoxin to Likuni phala during processing but limited information is available. Nixtamalization or alkali cooking of maize and maize products has been found to effect beneficial properties including reduction of aflatoxin contents. This study was therefore designed to assess the levels of aflatoxin contamination of Likuni phala porridge flour and the efficacy of cooking the porridge with lime (nixtamalization) to reduce the aflatoxin contamination to tolerable levels. Three samples of the product were each taken at two week intervals from three manufacturers in three different districts of the Southern Region of Malawi. Two factories were of the cottage type and one was large. The samples were analysed for total aflatoxin, then cooked into porridges with addition of lime at levels ranging from 0.1% to 0.8% based on dry product. The porridges were analysed for total aflatoxin, proximate composition and subjected to sensory evaluation. Potential exposure to aflatoxin and the dietary contribution to intakes of protein, energy and calcium on young children were also calculated. x Results showed that aflatoxin levels were lower than the tolerance of 10μg/kg in the samples from the two cottage industries where the average was 0.4μg/kg and 0.7μg/kg, but all the three samples from the large factory contained aflatoxin well above the tolerance for total aflatoxin with an average of 20.5μg/kg. On cooking the samples with addition of lime, the porridges were acceptable up to 0.4% lime addition, and the aflatoxin levels reduced to way below the tolerance levels even with the lowest level of lime addition of 0.1%. The potential aflatoxin exposure to children was correspondingly reduced. Results of proximate composition of the porridges cooked with addition of lime showed increases in total ash from 2.07% to 2.45%, calcium from 123mg/100g to 242mg/100g and fibre levels from 3.15% to 5.4% and decreases in crude fat levels from 5.72% to 2.38%. Nixtamalization slightly improved the intake of protein and calcium by the children. The study concluded that Likuni phala generally contains higher levels of aflatoxin than the tolerance limit and these levels are not reduced significantly by cooking using the recommended method. However, cooking with addition of lime up to 0.4% resulted in porridges that were acceptable; with aflatoxin levels well below the tolerable levels and therefore low aflatoxin exposure to young children in addition to improvements in selected nutrients’ intake.