Optimization of pectin yield extracted from coffee Arabica pulp using response surface methodology

Pectin was extracted from coffee pulp using 0.1 M H2SO4. The Box Behnken Design based Response surface methodology was applied to optimize pectin yield. The impact of extraction time (45-75 min), temperature (80-100 °C), solid to liquid ratio (SLR) (1:20, 1:27.5, and 1:35), and pH (1.5, 2, and 2.5) on pectin yield were studied. Under optimal extraction conditions (84 °C, 75 min, SLR of 1:20 and pH: 1.5), physical, chemical, structural and antioxidant properties of pectin were examined. The results of the physicochemical analysis are: acetyl value: 1.10 ± 0.05 %, equivalent weight: 1429 ± 54 g/mol, anhydrouronic acid: 57.1 ± 0.9 %, degree of esterification: 78.5 ± 1.8 %, moisture content: 8.5 ± 1.5 % and ash content: 4.3 ± 0.9 %. FTIR analysis indicated the (-OH) peak of pectin was lower and shifted left compared to treated and untreated coffee pulp powder. SEM analysis shows a smoother surface, whereas XRD shows a less amorphous structure of pectin. The total phenolic and flavonoid content of coffee pulp pectin was found to be 26.7 μg Gallic Acid Equivalent/mg and 0.8957 μg Quercetin Equivalent/mg, respectively. Antioxidant analysis showed significant antioxidant properties (IC50 = 642.31 ± 30.43 μg/mL). The predicted and actual pectin yields at the optimal extraction condition were 14.39 and 13.7 %, respectively, with R² = 0.95 that indicate the model can represent the experiment. Therefore, achieving a maximum pectin yield with improved antioxidant and other physicochemical qualities ensures that coffee pulp can potentially serve as a viable commercial source of pectin.