Optimization of a gas-fired gurasa (local bread) baking oven using response surface methodology (RSM)

Abstract

Gurasa (local bread) is an important diet in many households in Northern parts of Nigeria for time immemorial, especially in Kano State, Nigeria. This study is to develop a gurasa baking oven, carry out the performance evaluation of the oven and also to optimize the baking parameters of the oven using the response surface methodology (RSM). The oven is composed of three baking compartments; these include a heat source, a control panel and the main frame. The baking compartments consist of heating rods and the gurasa baking trays. The heat source is a gas burner that generates the required heat to bake the products. There is a control panel that is used to set the temperature at which the gas cylinder goes off (after the preheating of the oven) and the heat in the oven is maintained for some time with the aid of the insulator in between the walls. Using the response surface method, the oven was evaluated to know its baking efficiency, baking damage, and capacity. The oven has a baking efficiency of 87.5 %, baking damage of 11.5 % and a capacity of 23.4 kg/hr with 27 loaves per batch. The RSM showed values of the responses ranged from 16 – 95 g, 5.24 – 13.6 %, 845.8 – 3684.2 N/m² and 0.7–8.06 cm³/g for weight loss, moisture content, tensile strength and specific volume respectively. Quadratic models to predict weight loss, moisture content, tensile strength and specific volume of gurasa in terms of baking temperature, baking period and mass of dough were developed. The optimum baking process was achieved at a baking temperature of 200^oC, a baking period of 9 minutes and a dough mass of 130 g. These values show that the oven can be adopted for domestic and commercial baking.