Orange Solid Waste Valorization: Optimization of Pectinase Extraction and Enzimatic Treatment of Orange Press Liquor

Abstract

During orange juice production only approximately a half of fresh oranges weight is transformed into juice while the other half is considered as production waste. Orange solid wastes can be pressed with lime to obtain a press liquor that is currently concentrated up to 65-70°Brix by multiple effect evaporation. A prior preconcentration step by reverse osmosis (RO) reduces significantly energy consumption during evaporation. However, RO treatment is not easily performed due to the high viscosity of the press liquor, attributed to the presence of pectic substances.
The aims of this work are to study the extraction of pectinase enzymes from orange peels, as well as to asses the effect of the enzyme extract on pectic content and viscosity of press liquor. Pectinmethylesterase enzymes were characterized in terms of the typical enzyme kinetic parameters. The optimum extracting conditions were pH=5.5 and NaCl=1.7 M. The characteristic kinetic parameters of the pectinmethylesterase were K_M=0.5 % and V_max = 2.3 mg/min·mL. The application of the enzymatic extract to real orange press liquor reduced considerably its pectin content (77.72 %) and viscosity (48.30 %), suggesting that enzyme extraction could be included as a step in the integrated valorization of orange wastes.