Extraction optimization and physicochemical properties of high methoxyl pectin from Ananas comosus peel using microwave-assisted approach

Food and agricultural wastes have led to environmental and landfill issues. Nonetheless, biowastes can be converted into valuable bioproducts, such as pectin. Hence, this study investigated microwave-assisted extraction (MAE) optimisation to extract pectin from pineapple (Ananas comosus) peel. Microwave power (400-600 W), pH (1.5-2.5), and solid-to-liquid (S/L) ratio (1:10-1:30 w/v) were applied to optimise pineapple peel pectin (PPP) extraction, as well as to determine the interaction effects on pectin yield and anhydrouronic acid (AUA) content using Box-Behnken Design (BBD). The highest yields of pectin (2.43 +/- 0.03%) and AUA content (54.61 +/- 0.21%) were achieved at optimised conditions (600 W, pH 1.52, and 1:10 g/mL of S/L ratio), which were 35.75% and 7.93% higher than their values prior to optimisation, respectively. The PPP displayed Newtonian behavior at low concentrations (0.1, 0.5, and 1.0% w/v), but showed pseudoplastic flow behavior at a higher concentration (2.0% w/v). The PPP viscosity was temperature-dependent, as its apparent viscosity gradually decreased with temperature increment from 25 to 75 degrees C with increasing shear rate. The PPP emulsion stability improved by 1.06- and 1.12-fold after 30 days of storage at 4 and 25 degrees C, respectively, in comparison to commercial pectin. The MAE method enhanced the pectin yield by 21.5% than the conventional heating technique. The MAE qualifies as an alternative for pectin extraction from pineapple peel, as it demands less solvent and shorter extraction time.