Optimization of amount of spices, roasting temperature and time for field pea (PisumSativum) Shiro flour using response surface methodology

Abstract

Shiro flour is widely used in both rural and urban parts of Ethiopia in the form of stew or wot with flat bread or injera. Preparations of shiro flour depend on the tradition and economic status of the community. The basic shiro flour processing steps are similar. But, every processer and community has its own recipe and practice. This attributes shiro flour to have different nutritional value and sensory attribute that could affect marketing and consumer acceptability. The aim of this study was to optimize amount of spices, roasting temperature and time of shiro flour and evaluate the effects of each variable on chemical composition. Field pea were roasted in a digital hot plate using roasting temperature and time combination of 109 °C, 120 °C, 135 °C, 150 °C, and 160 °C for 2, 3, 4, 5, and 6 min, respectively. A response surface methodology with central composite rotatable design was used to carry out this study using design expert version 7. Significance of model was calculated using analysis of variance (ANOVA). The result show that both roasting temperature and amount of spices significantly (p<0.05) affected the proximate composition of field pea shiro flour. Amount of spices mainly affected mineral content. Whereas, roasting temperature influenced sensory property of the field pea shiro wot. The optimized roasting condition and amount of spices for preparing better quality shiro flour was found to be roasting temperature at 150 °C for 5 min and incorporating 15% total spices. The chemical composition of field pea shiro flour at optimum condition was found to be moisture 6.36%, crude fat 2.47%, crude protein 24.70%, ash 3.31%, carbohydrate 59.15%, energy 357.59%, iron 15.59 mg/100 g, calcium 119.43 mg/100 g, potassium 1153.07 mg/100 g, phosphorus 250.94 mg/100 g, zinc 4.3 mg/100 g, taste 6, and overall acceptability 6.11. This indicated that manipulation of quality of shiro flour can be done by controlling at least one aspect of the preparation techniques studied (spices, temperature and time).