Extrusion of apple pomace facilitates pectin extraction

Twin-screw extruder was employed to disintegrate apple pomace (AP) to facilitate production of apple pectins by 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 x intrinsic viscosity (Y[η]), was an objective function for optimizing conditions for the solubilization of AP polysaccharides. Y[η] of pectins in extruded WSP ranged 0.59-1.34, while acid extracted WSP had Y[η] of 1.12. Extruded WSP with Y[η] comparable to acid extraction was obtained in the SME ranges of 110-170 kWh/h.