Pectin Extraction Process from Cocoa Pod Husk (Theobroma cacao L.) and Characterization by Fourier Transform Infrared Spectroscopy

Abstract

The Cocoa Pod Husk (CPH) accounts for 67–76% of the total cocoa fruit weight, making it its main agro-industrial waste of cocoa production. A valorization of this waste is possible through the extraction of pectin. In this study, pectin was extracted from CPH powder by acid hydrolysis using citric acid and sulfuric acid. Fourier transform infrared spectroscopy (FT-IR) was employed as a qualitative and quantitative characterization technique. The FT-IR of the pectin samples showed the bands visible at 1732 and 1626 cm−1 corresponding to the esterified and free carboxylic groups, respectively. These bands can be differentiated according to their degree of methyl esterification (DE) by analyzing the area under the curve. The extracted pectin showed no significant difference in yields (p ≤ 0.05) between the two acids; however, significant differences (p ≤ 0.05) were observed in DE and methoxylation percentage (MeO). According to the FT-IR results, pectin extracted with citric acid presented a lower DE (7.43%) and MeO (1.12%) compared to pectin extracted with sulfuric acid, which showed a DE of 18.15% and a 2.96% MeO. Pectin with a DE below 50% is classified as low-methylated, making it unsuitable for the food industry. However, these create a raw material that has a potential use in the pharmaceutical and bioenergy industries.