Extrusion of Apple Pomace Facilitates Pectin Extraction

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Abstract
Twin‐screw extruder was employed to disintegrate apple pomace (AP) to facilitate production of apple pectins by hot water extraction. AP was extruded under different conditions of screw speed, 250‐350 rpm; feed rate, 30‐40 kg/h; moisture, 20‐30%. The yield of water soluble polysaccharides (WSP) increased with increasing specific mechanical energy (SME), but intrinsic viscosity decreased with increasing SME. Considering both the WSP yield (g/dL) and intrinsic viscosity (dL/g), a dimensionless term, product yield ∞ intrinsic viscosity (Y[]), was an objective function for optimizing conditions for the solubilization of AP polysaccharides. Y[] of pectins in extruded WSP ranged 0.59‐1.34, while acid extracted WSP had Y[] of 1.12. Extruded WSP with Y[] comparable to acid extraction was obtained in the SME ranges of 110‐170 kWh/h.