Chemical Modification and Cowpea Fortification of Maize

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1999-12

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University of Ghana

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The high utilization and consumption levels of maize in developing countries call for the investigation of new methods of processing to introduce variety as well as improve the functionality and nutrient quality of maize-based foods. This study was carried out to determine the effect of nixtamalization, fermentation and cowpea fortification on maize and to identify the dominant microflora in fermented nixtamalized maize. The effect of cooking and lime concentration was determined using a 2x4 factorial experimental design, with cooking time (0, 30 mins) and lime concentration (0,0.33,0.5 and 1.0%). The cooking time and lime concentration , significantly influenced the moisture absorption, pH and colour of the samples. Water absorption capacity was dependent on the lime concentration. These indices increased with increasing lime concentration used. The lime did not significantly alter cooked paste viscosity, ash and protein content. A 3 x 4 factorial experiment was used to study the effect of fermentation on the characteristics of nixtamalized maize dough. Fermentation resulted in decreased pH with a corresponding increase in titratable acidity. Fermentation decreased the texture, water absorption capacity (25°C), cooked paste viscosity and colour intensity of nixtamalized maize dough. Traditional maize dough facilitated fermentation, by acting as a starter culture to produce lower pH and higher acidity in the steeped:nixtamalized maize dough blends. The central composite rotatable design for K = 3 was used to study the combined effect of lime concentration (0- 1%), moisture content (55-65%) and cowpea leve (0-30%) on pH, titratable acidity, water absorption, texture, protein and viscosityof nixtamlized maize dough (masa) during fermentation. The lime and cowpea influenced the titratable acidity, water absorption capacity, protein content and the cooked paste viscosity of the fermented cowpea fortified nixtamalized maize. Increasing concentration of lime, during fermentation, generally decreased titratable acidity, water absorption, work required to back extrude an amount of cooked set slurry and cooked paste viscosity while the addition of cowpea increased most of these indices. The final pH and titratable acidity of the fermented nixtamalized maize were comparable to that of the traditional maize dough. The microbial counts obtained (aerobic mesophiles and lactic acid bacteria) for the nixtamalized maize and traditional maize dough, were comparable after 24 hours of fermentation. Yeast counts were slightly lower in the fermented nixtamalized maize dough. These results showed that nixtamalized maize dough lends itself well to traditional spontaneous fermentation with the resultant souring and development of the characteristic flavours of traditionally fermented maize. The Lactic acid bacteria identified in the fermented masa were L. plantarum, L. fermentum and L. cellobiosus. Pediococcus spp. were also identified (found in fermented masa).

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Thesis (MPhil.) - University of Ghana, 1999

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