Improvement in maize bread quality through addition of pre-gelatinized starch, sourdough in combination with dough sheeting

Abstract

Wheat bread is a staple food product that is not easily accessible to many people in sub-Saharan Africa as it is relatively expensive. This is due to the regions climatic conditions which are not generally suitable for wheat cultivation. Hence, most wheat has to be imported. Maize is potentially a suitable alternative for production of bread and other dough-based products since it is widely produced under diverse environments in sub-Saharan Africa. However, maize does not possess unique viscoelastic gas-holding properties like wheat. The effects of dough sheeting on the quality of maize dough and bread were investigated. Dough sheeting in combination with maize flour starch pre-gelatinization, zein, sourdough fermented maize flour and surfactant (DATEM) addition were investigated. Dough sheeting is a simple technology that has been used for development of dough from wheat flour of low protein quality. Dough sheeting of maize flour without pre-gelatinization produced a crumbly dough, whereas sheeting in combination with starch pre-gelatinization produced a cohesive dough with dramatically improved dough handling properties. Tensile tests showed development of a smoother texture on maize dough as the number of sheeting passes increased from 5 to 40. Zein dough addition (mixed above its glass transition temperature in water) in combination with dough sheeting formed a more elastic maize dough. CLSM revealed intermingling of fibrils from the added zein within the maize dough which was presumably responsible for the improvement in viscoelastic properties of the composite. Alveography revealed that maize-zein doughs retained gases well but that increasing sheeting passes reduced stability and extensibility. Maize bread had undesirable cracks on the crust. With zein addition, there was a reduction in the cracks. DATEM addition improved bread crumb structure, preventing the formation of holes. This was thought to be due to hydrophobic and hydrophilic interactions between starch and protein of maize flour and the DATEM. Dough sheeting in combination with sourdough addition and pre-gelatinized maize produced maize bread with improved loaf height. Stereomicroscopy of the crumb of maize sourdough bread showed a more continuous crumb structure. It is proposed that the improvement of maize bread by sourdough addition is due to the sourdough inducing softening and modification of starch, making dough less elastic but improved ability of the maize dough to trap carbon dioxide and withstand pressure of expanding gas. The study shows that dough sheeting together with pre-gelatinization of some of the maize flour improves dough handling and functional properties of maize doughs when applied in combination with other treatments. The best combination for maize bread was found to be dough sheeting at 15 passes, pre-gelatinization together with addition of sourdough and DATEM. Dough sheeting in combination with pre-gelatinized maize flour, addition of maize sourdough and DATEM could form a relatively inexpensive and predominately natural way of producing gluten-free breads.