Extraction of pectin and polyphenols from coffee pulp and peel for jam production

Abstract

The pulp and peel of coffee cherries, which are by-products of coffee bean processing, are rich in valuable bioactive compounds. However, these by-products are typically repurposed as fertilizers, fuel, or substrates for mushroom cultivation. This study focuses on optimizing the extraction conditions for pectin and total polyphenols from these by-products through treatment with cellulolytic enzymes. The materials used in the study were derived from the pulp and peel of two coffee varieties: Arabica and Robusta. The research examined various parameters that affect the extraction process, including the cellulase enzyme content (from 0 to 800 U/g of raw material), the pH of the extraction solvent mixture (from 4.0 to 5.7), extraction temperature (from 40°C to 60°C), the solvent-to-material ratio (from 4: 1 to 12: 1) and the extraction duration (from 30 to 90 minutes). The results indicate that the optimal conditions for pectin extraction are a temperature of 55°C, a pH of 5.0, a solvent-to-material ratio of 8: 1 and an extraction time of 75 minutes. Under these conditions, the extract obtained from Robusta coffee yields 17.91 ± 0.33 g of soluble solids, 1.70 ± 0.01 g of pectin and 7.11 ± 0.14 g GAE per liter. In contrast, Arabica coffee yields 9.77 ± 0.07 g of soluble solids, 1.61 ± 0.03 g of pectin and 0.53 ± 0.02 g GAE per liter under similar conditions. The extracts were subsequently filtered, concentrated and adjusted with citric acid and sugar to achieve a pH of 3.0 and a solid soluble content of 65%, followed by pasteurization and bottling to produce jam. Although the final product exhibits a structure similar to commercial jams, it retains a certain bitterness, indicating a need for further refinement in product development.