Optimization of bioprocessing parameters using response surface methodology for bael (Aegle marmelos L.) wine with the analysis of antioxidant potential, colour and heavy metal concentration

Abstract

Wine prepared from the tropical fruit bael (Aegle marmelos L.), known for its medicinal properties, is a novel beverage rich in antioxidants having enough credibility for projecting it as a medicinal wine. In the present study, bael, which is abundantly available in the region, was selected for wine production and its alcohol content was estimated using gas chromatography analysis. The conditions for the fermentation were optimised using response surface methodology. The quantitative effects of temperature, pH and duration of fermentation were investigated on fermentation of ethanol from bael using wine yeast Saccharomyces cerevisiae (NCIM 3315) as the starter culture. The optimum conditions for a 8.13% yield of ethanol were found to be temperature of 34℃, pH of 4.5 and duration of fermentation of 48 h. Biochemical analyses were conducted to study the proximate attributes of the pulp and wine with their respective changes due to fermentation. The raw bael pulp had total soluble solids 22.31°Brix, pH 5.33, total phenolics 1.94 g/100 ml and carotenoids 32.98 µg/g dw; the wine had total soluble solids 3.3°Brix, pH 4.54, total phenolics 0.96 g/100 ml and carotenoids 29.90 µg/g dw. The bael pulp and wine had 2,2-diphenyl-1- picrylhydrazyl (DPPH)-scavenging activity of 70.99% and 49.03% respectively. The Hunter colour values of the bael pulp and wine were also evaluated and the results are presented. In this study, heavy metals like Cu (0.219 mg/l), Pb (0.190 mg/l), Zn (0.002 mg/l) and Fe (3.296 mg/l) were found in the wine. The structural feasibility of bael as an effective substrate for fermentation was also confirmed by scanning electron microscopy studies.