Production of pectin pomace and recovery of leach liquids from orange peel

This paper summarizes the results of an experimental investigation aimed at the processing of orange peel to produce pectin pomace. Leach liquids produced from orange peel during the process had the following waste treatment properties: COD, 11 ppm; BOD, 7.8 ppm; settleable matter 160 ppm; turbidity, 1100 NTU. The presence of water-soluble pectin 34 mg/100 g in the dilute leach liquids contributed to high viscosities and made concentration by evaporation difficult. Treatment of the peel with pectolytic enzymes resulted in increasing the yield of recoverable soluble solids from 57 to 65.5 kg soluble solids/ton peel. Enzyme-treated liquids were concentrated to 70 degrees Brix and relative viscosity of 3400 centipoise; however due to gel formation non-treated liquids cannot be concentrated to over 35 degrees C Brix due to high viscosity (over 20,000 centipoise). Careful use of enzymes to increase the soluble solids yield or lower viscosity during leaching of the peel did not affect the degrees Brix, pH, or clouding ability of the concentrated peel leach liquids. Based on the results of this work, a flow diagram and material balance of a citrus orange pectin pomace production process is presented. (C) 1996 Elsevier Science Limited.