OPTIMIZATION OF VARIABLES IN EXTRACTION OF PECTIN FROM WATERMELON RIND AND ITS EVALUATION

Abstract

This study investigated watermelon rind, an underutilized agro-waste, as a potential source of pectin and its application in pineapple jam. Pectin was extracted using ethanol as the precipitant, citric acid used to adjust the pH levels (2.0, 2.5 and 3.0). The extraction was carried out at different temperatures (70°C, 80°C, 90°C) and times (70 min, 80 min, 90 min) while maintaining a constant solid-to-liquid ratio of 1:20 (w/v). Experimental design was performed using Design-Expert®️ version 13 and data were analyzed with IBM SPSS Statistics version 25. The maximum pectin yield (20.25%) was obtained at pH 2.0 (90°C, 80 min). At pH 2.5, the extracted pectin showed desirable quality parameters including moisture (10.5±0.2%), ash (7.8±0.16), equivalent weight (735.62±0.52), methoxyl content (6.3±0.07), anhydrouronic acid (59.73±0.42%) and degree of esterification (59.87±0.3%) confirming its classification as high-methoxyl pectin. Pectin with the highest yield from each pH level was applied in pineapple juice to prepare jam. Sensory evaluation revealed that jam prepared with rind-derived pectin was comparable in color, flavor, taste, texture and overall acceptability to jam prepared with commercial pectin. The best-performing jam (from pH 2.5 at 90°C, 90 min) was then subjected to physicochemical analysis, showing TSS (68°Bx), acidity (0.70%), reducing sugar (30.83%), total sugar (62.5%), moisture (33.46%) and vitamin C (17.43 mg/100g). The study demonstrated that watermelon rind pectin is a functional, eco-friendly, and cost-effective substitute for commercial pectin, contributing to waste valorization and sustainable food processing.