Effect of soy fortification method on the fermentation characteristics and nutritional quality of fermented maize meal

Abstract

Studies were conducted to develop an appropriate household/smallscale enterprise level technique for the production of soyfortified fermentedmaize dough (ormeal) by comparing different treatments, processing methods and fortification levels. The effects of fortification method of the Ghanaian traditional fermented maize dough with raw or heat treated whole soybeans and fullfat soyflour at 0%, 10% and 20% replacement levels, on the rate of fermentation and product quality were investigated. Sensory characteristics, trypsin inhibitor activity, amino acid pattern, proximate composition and hot paste viscosity were used as the indices of quality. Addition of whole soybeans to maize before milling and fermentation reduced the fermentation time by 60% while increasing the protein content by 24% and 70% respectively for 10% and 20% levels of fortification. A significant improvement was also achieved in the amino acids pattern of the fortified dough. However, raw whole soybeans imparted an undesirable color and beany flavor and an appreciable concentration of trypsin inhibitor activity (TIA) to the dough. Boiling soybeans for 20 min before incorporation into the maize for milling and fermentation was found necessary for desirable flavor and low levels of TIA. Little or no changes in the pasting viscosity characteristics occurred in samples containing boiled soybeans, while the usual method of fortifying maize meal with soy flour was found to severely depress the pasting viscosity characteristics and drastically reduced the acidity of the fermented dough. Based on the findings of the study, the most appropriate technique for the production of soyfortified high protein fermented maize dough has been suggested to involve incorporation of boiled whole soybeans in soaked maize before milling and fermentation for improved sensory characteristics, enhanced nutritive value and optimal functional properties