Enhancing nutritional benefits and reducing mycotoxin contamination of maize through nixtamalization
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This study analyzed the effect of nixtamalization using slaked lime (Ca(OH)2) and wood ash on the mycotoxin content, nutritional composition, physicochemical and sensory properties of Ugandan maize. Maize samples (6 samples of 5kg) were purchased from each of the four maize growing districts of Uganda (Mubende, Kiryandongo, Gulu and Iganga) and two maize collection centers (Nateete and Kisenyi) in Kampala Capital City. The samples were nixtamalized before milling into flour using a grain grinder (model SZ-1000-3) manufactured by Guangdong in China. The nixtamalization process involved;(a) soaking maize grains overnight in 1% slaked lime (Ca(OH)2) solution and (b) soaking maize grains overnight in a 1% traditional liquid ash solution. The maize grains from each solution were washed in clean water three times and dried at 60°C for 16 hours to constant weight and ground into flour, which was further analyzed for aflatoxins and fumonisin, fat, dietary fibre, total sugars, protein, and niacin content as well as digestibility. Furthermore, viscosity and sensory acceptability of the paste (posho) and porridge prepared from the flours from the nixtamal and non-nixtamalized maize were determined. Nixtamalization of maize using both slaked lime and local ash significantly (P<0.05) reduced aflatoxin (up to 90%) and fumonisin (up to 80%) levels in maize. In terms of nutrient content, nixtamalization resulted into a slight reduction in fat, sugars, protein and dietary fibre, but significantly (P<0.05) increased ash and niacin content of maize. Nixtamalization had a significant effect on the pasting properties of maize flour. Flour prepared from maize nixtamalized with lime significantly (P<0.05) recorded the lowest peak viscosity (711cP) compared to flour prepared from maize nixtamalized with ash (1377cP) and non-nixtamalized (1465cP). Overall, there was no significant difference among the sensory properties (general appearance, colour, aroma, thickness, taste, mouth feel and overall acceptability) for porridge and posho prepared from nixtamal and non-nixtamal (control) maize flour samples. Based on the findings of this study, nixtamalization is effective in improving the quality and safety of maize. Thus, scaling up of nixtamalization in the country, could lead to a significant reduction in exposure to aflatoxins and fumonisin.