Factorial experimental design for optimizing the roasting condition of banana peel (Musa paradisiaca var Semeru): characteristics and antioxidant activity

Abstract

Banana peel is an organic waste that has not been widely used. The rich content of vitamins, minerals, antioxidants and tryptophan is the background for research utilizing organic waste for something useful. This study aimed to use a factorial design to find the optimum conditions for the banana peel roasting process. The variables analyzed were roasting temperature (180°C and 200°C) and roasting time (15 and 20 mins). Responses to determine the optimum conditions were water content, color similarity with local coffee products and antioxidant activity (IC50). Antioxidant activity was measured using the 2,2- diphenyl-1-picrylhydrazyl method. The characteristics of banana peel powder and roasted banana peel powder showed the presence of beneficial substances and even richness in vitamins and minerals, as well as the presence of tryptophan. The scavenging activity of roasted banana peel powder was higher at high temperatures and longer during roasting. The lowest water content was at 200°C and 20 mins of roasting conditions. A brownish color resembling ground coffee was obtained with a roasting temperature of 200°C. The interaction between temperature and roasting time affects the moisture content and color similarity, while the roasting time dominantly affects IC50. The optimum conditions selected were 200°C roasting conditions; 20 mins will produce a water content of 2.00%, color similarity 11.80 and IC50 1979.2 (ppm). In addition, the presence of tryptophan in banana peel powder has the opportunity to be used as an antidepressant compound.