Optimization of alcoholic fermentation of dragon fruit juice using response surface methodology

Abstract

In recent years, dragon fruit has been applied in food processing with various products. The purpose of this study aimed to valorize a fermented fruit drink from a Vietnamese local dragon fruit by alcoholic fermentation of the juice using Saccharomyces cerevisiae. Response surface methodology was applied to find the optimal condition of varied factors including total soluble solids content, inoculum size of the yeast and fermentation time. The experiments were carried out according to the central composite design with the sugar content ranged from 16 to 20°Brix, the inoculum size from 1 to 3% yeast and the fermentation time from 40 to 48 hrs. A quadratic model was respectively developed to correlate the investigated variables to the remained sugar content and ethanol yield of the product. The optimized conditions for fermentation were selected as 18°Brix of initial fruit juice; 2% v/v of added yeast inoculation rate and 44-hours fermentation time. Under these conditions, final fermented dragon fruit juice achieved alcohol content of 3.54% v/v with remaining sugar content of 14.6°Brix and a level of ‘moderately like’ obtained by sensorial evaluation.