Optimization of pectin yield extracted from coffee Arabica pulp using response surface methodology
Girma Biratu, Henock Woldemichael Woldemariam, Girma Gonfa
Abstract
Pectin was extracted from coffee pulp using 0.1M 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 R 2 = 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.