Functional Biscuits from Wheat, Soya Bean and Turmeric (Curcuma Longa): Optimization of Ingredients Levels Using Response Surface Methodology

This study aimed at producing composite biscuits from wheat flour, soya bean and turmeric (Curcuma longa) as a functional food. An experimental design was used to optimize the mixture of the variables by mixture response surface methodology. This produced eight experimental runs. The variables considered were wheat flour, soybean flour, and turmeric powder, while the responses were moisture content, protein content, fat content, DPPH free radical scavenging power, phenolic content, total antioxidant and reducing power. The colour characteristics and the sensory attributes were analysed and compared with those of wheat biscuit (100% refined wheat flour).. Turmeric powder had the highest positive influence on the antioxidant properties while soybean had the highest effect in improving the nutritional composition (protein,) of the biscuits. The optimum composite flour blends for biscuit production consisted of 72.88%, 26.63% and 0.5% of wheat flour, soybean flour and turmeric respectively. The optimum combination consisted of 6.59% moisture, 21% fat, 13.01% protein, 48.77% DPPH, 0.74mgGAE/g phenolic, 3.78mgGAE/g total antioxidant and 1.59mg/ml reducing power. Regression analysis of the model indicates that significant interaction exists between the ingredients with high coefficient of determination (R2). The high R2 values showed jthat the model developed for the responses appeared adequate for predictive purposes. The experimental and predictive values were closely related, showing that the models correctly predicted the response variables. From this study, it can be concluded that addition of turmeric into composite flour biscuit will improve its nutritional composition and functionality.

Keywords: Turmeric, Antioxidant activity, Biscuits, Variables optimization, mixture response surface.