Citrus peels are considered a rich source of valuable biomolecules. Pectin is a polymer of polysaccharide acid and is composed of galacturonic acid monosaccharides. In this study, response surface methodology was used to optimize pectin extraction from Citrus × clementina Hort. ex Tan. (Rutaceae) peels using citric acid as an extraction solvent. The effect of the parameters conditioning the extraction process and pectin yield (pH level, temperature, extraction time, solid/liquid ratio, and raw material particle size) was investigated using a Box-Behnken design. The quality of the extracted pectin was assessed both chemically (moisture, ash, protein, and carbohydrate content) and functionally (gelling power and emulsifying activity). According to the screening experiment, the pH level, temperature, and particle size were the main factors influencing the pectin yield. The adjusted mathematical model enabled us to plot response surfaces in order to determine the optimal extraction conditions. The highest production yield of pectin (26.6%) was obtained at the optimal conditions of pH = 1.5, temperature = 100 °C, and particle size = 0.1 mm for an extraction time of 30 min. Compared to the predicted value of 26.6%, the experimental extraction yield of C. clementina was about 21.4% of pectin. Concerning the functional properties, the extracted pectin had a high gelling power of 164 ° SAG and an emulsifying activity of 38.5%.
Keywords: characterization; citrus by-products; functional properties; optimization; pectin extraction; response surface methodology.