Optimization of Temperature and Time on Pregelatinization of Black Potato Flour (Solenostemon rotundifolius) Using Response Surface Methodology. Jhauharotul Muchlisyiyah, Tanalyna Hasna, Teti Estiasih, Susi Wardhani
Food Science and Technology Department, Agricultural Technology Faculty, Universitas Brawijaya, Jl Veteran, Malang, Indonesia
Abstract
Black potato (known as kentang hitam/Coleus tuberosus) is a tuber tubers that had a lot of functional use. Like other tubers, its flour is underutilized because it is need to be improved. Flour improvement can be done by modification. Simple flour modification can be obtained by conducting pre-gelatinization to increase the solubility index and water absorption, therefore the optimum temperature and time on pre-gelatinization of black potato flour are necessary. The objectives of the study were to determine the physicochemical and functional characters of pre-gelatinized black potato flour and to determine the temperature and time of the pre-gelatinization process of black potato flour which produced the optimum characteristics of the Water Absorption Index (WAI) and Water Solubility Index (WSI). This study uses the Responnse Surface Methodology (RSM) method with two variables, temperatures of 50, 60, 70 oC and time is 3, 7, 11 minutes. The desired response is the Water Absorption Index and Water Solubility Index. The WAI and WSI responses obtained are quadratic with the equations Y = + 2.65 + 0.038 A + 0.032 B - 0.043 AB - 0.062 A2 - 0.028 B2 and Y = +8.22 + 0.29 A + 0.090B - 0.29 AB - 0.43 A2 - 0.075 B + 2. A = process temperature (oC), B = length of cooking (minutes). Optimal WAI and WSI responses at 62oC and 8.44 minutes. Pasting characteristics which includes temperature, pasting viscosity, hot paste viscosity, breakdown, final viscosity, setback, and peak time of pregelatinized Black potato flour was lower than native flour. All texture parameters which includes hardness, springiness, gumminess, cohesiveness, gumminess, chewiness, resilience of pregelatinized Black potato flour were lower compared to native flour, except for higher cohesiveness and resilience. The morphology of pregelatinized Black potato flour granules become more mingled a with each other, rougher, and swollen granules. The crystallinity of pregelatinized Black potato flour decreases from 6 peaks to 4 peaks compared to native flour. The enthalpy of pregelatinization process of black potato flour is 5.03 kJ/kg
Keywords: Coleus Tuberosus, Pregelatinized flour, Response surface methodology, water absorbtion index, water solubility index
