Comparison of ultrasound-assisted and conventional extraction for recovery of pectin from Gac (Momordica cochinchinensis) pulp

Abstract

Gac (Momordica cochinchinensis) is commercially used for production of Gac oil. Gac pulp, which accounts for 40-50% of fruit weight, is major by-product. This study aimed to optimise extraction conditions including pH, temperature, time, ratio and ultrasonic power for recovery of pectin from Gac pulp, and compare its properties using ultrasound-assisted extraction (UAE) and acidic hot water extraction (AHWE) techniques, the typical advanced and conventional techniques for pectin extraction. Response surface methodology with Box-Behnken design was applied for both techniques. The results showed that pH was the most influential factor. Optimal AHWE conditions were identified at 90°C for 100 min with solvent to sample ratio of 50 mL/g and pH of 1.5, while optimal UAE conditions were 35 min, pH of 1.5, and ultrasonic power of 200 W. The recovery yield of pectin from UAE (53.80% ± 6.04) was significantly higher than that of AHWE (42.97%± 5.08). Pectin obtained from two techniques were low methoxyl pectin (DE < 50%) with good solubility, potent free radical scavenging capacity, and similar structure. As UAE has advantages of short extraction time, more efficient recovery of pectin with better properties, UAE is recommended for recovery of pectin from Gac pulp for further applications.