Optimization of Extraction of Pectin from Jackfruit Peel by Ultrasonic-assisted Enzymatic Method and Modification of De-Esterification

In order to improve the yield of jackfruit peel pectin (JFPP) and obtain high-purity pectin with good functional properties, this study optimized the extraction process of pectin by ultrasound-assisted cellulase enzyme method through response surface experiments. The extracted pectin was preliminarily purified, including degreasing, deproteinization, decolorization, and dialysis concentration process. The purified pectin was then enzymatically esterified and modified by de-esterification to obtain de-esterified jackfruit peel pectin (DE-JFPP), and a comparative analysis was conducted on the basic composition, molecular weight, monosaccharide composition, functional group characteristics, thermal stability, and microstructure of the pectin before and after modification. The results showed that the optimal conditions for the extraction process were enzyme dosage of 0.7%, the enzymatic hydrolysis temperature of 30.4 ℃, and the pH of 4.6. It was observed that the yield of JFPP was 15.26%±0.07% under the specified conditions. The galacturonic acid content in the modified pectin increased from 79.10% to 83.24%, with a decrease in total sugar content from 43.42% to 41.90%, a decrease in esterification degree from 84.25% to 32.36%, and a decrease in weight-average molecular weight from 29.24 ku to 28.49 ku. Both JFPP and DE-JFPP contained eleven monosaccharides and belonged to the RG-I pectin with a decrease in the degree of branching in DE-JFPP. Fourier transform infrared (FTIR) spectroscopy demonstrated that both the pectin before and after modification had characteristic absorption peaks of pectin, and the peak area corresponding to the esterified carboxyl acid group decreased after modification. The JFPP and DE-JFPP demonstrated high thermal stability, with solubilization temperatures of 160.22 ℃ and 123.28 ℃, and degradation temperatures of 255.11 ℃ and 230.56 ℃, respectively. Scanning electron micrographs (SEM) showed that JFPP had a smooth surface and a compact structure, and DE-JFPP had a rough surface and a loose structure. This study optimized the extraction process of jackfruit peel pectin, improving its yield. Results demonstrated that the esterified pectin had favorable physicochemical properties and microstructure, meeting requirements for gel carrier systems in various fields and expanding the utilization space of jackfruit peel pectin.