Effects of Drying Method and Extraction Solvent on Total Polyphenol Content and Antioxidant Activity of Asam Kandis (Garcinia xanthochymus Hook. f.) as a Traditional Natural Acidulant of Minangkabau Cuisine

Abstract

Asam kandis (Garcinia xanthochymus Hook. f.) is a traditional natural acidulant endemic to West Sumatra and widely used in Minangkabau culinary heritage, particularly in gulai and rendang. The fruit belongs to the genus Garcinia (Clusiaceae), recognized as a rich source of bioactive xanthones, benzophenones, flavonoids, and hydroxycitric acid with significant antioxidant, antimicrobial, and anti-inflammatory properties. Despite its long-standing culinary importance, post-harvest handling remains largely uncontrolled, with sun-drying persisting as the predominant technique without standardization of temperature or duration. This study systematically evaluated the effects of four drying methods (sun drying, oven drying at 50°C, 60°C, and 70°C) on physicochemical characteristics of dried asam kandis, and the influence of three extraction solvents (water, 70% ethanol, and 70% acetone) on total polyphenol content (TPC) and DPPH radical scavenging activity (IC50). A 4 × 3 factorial Completely Randomized Design with three replicates was employed; data were analyzed by two-way ANOVA and Duncan's Multiple Range Test at 5% significance. Drying method significantly influenced moisture content (12.4% sun drying to 7.9% oven 70°C), water activity (0.58 to 0.39), total acidity, and colorimetric lightness (L*). Total polyphenol content and antioxidant activity were significantly affected by both drying method, extraction solvent, and their interaction (p < 0.05). Oven drying at 50°C combined with 70% ethanol extraction yielded the highest TPC (124 mg GAE/g) and strongest antioxidant potency (IC50 52 µg/mL), while sun drying combined with water extraction produced the poorest results (62 mg GAE/g; IC50 142 µg/mL). A strong negative correlation was observed between TPC and IC50 DPPH (r = −0.96), confirming phenolic compounds as the principal contributors to antioxidant activity. These findings provide the first systematic evidence that oven drying at 50°C and 70% ethanol extraction represent the optimal processing combination for preserving and maximizing the bioactive value of asam kandis, with important implications for quality standardization, value-added product development, and the preservation of Minangkabau culinary heritage.