Thermomechanical process intensification for oil extraction from orange peels

The study investigated the intensification and improvement of oil extraction from orange peel through a thermomechanical process: the instantaneous controlled pressure drop (briefly D.I.C. process). This process involves subjecting orange peel for a short time to steam pressure, followed by an instantaneous decompression to a vacuum at 50 mbar. Central composite design was used to study the combined effects of processing steam pressure (1-7 bar; which corresponds to a temperature ranging between 100 degrees C and 162 degrees C respectively), processing time (0.3-3.7 min) and initial moisture content of orange peel before thermomechanical oil extraction (9.8-60.2% on dry material basis). The quantitative analysis, have been undertaken on oil present in orange peels. after processing. Correlation analysis of the mathematical regression model indicated that quadratic polynomial model could be employed to optimize the extraction of oil from orange peel. From response surface plots, the three variables exhibited a linear effect with the strongest effect for the processing pressure. The optimum reaction conditions selected with response surface analysis were as follows: steam processing pressure: 6.6 bar, processing time: 3.68 min, initial moisture content: 53.6% d.m. basis. Under these conditions, experimental yield of orange peel oil was close to predicted value (99%) calculated from the polynomial response surface model equation. A kinetic study indicated that extraction performed by D.I.C. process is clearly quicker than conventional steam distillation method. Industrial relevance: World production of citrus fruit has experienced continuous growth in the last decades of the XX century. Total annual citrus production was estimated at over 105 million tons in the period 2000-2004 (http://www.unctad.org/infocomtn/anglais/orange/market.htm). Oranges constitute the bulk of citrus fruit production, accounting for more than half of global citrus production in 2004. Thus, the quantities of generated by-products are very important. In this study, extraction of oil from orange peel was performed through a thermomechanical process developed in our laboratory. We report on some results obtained using this process as well as others comparing extraction kinetics when using a conventional steam distillation process and the proposed extraction process. One of the advantages of the described method is the short contact of extracted oil with the heated zones in the apparatus resulting in a lower heating period of the product compared to steam distillation. At industrial scale, this is interesting regarding oil quality and energy saving. (C) 2009 Elsevier Ltd. All rights reserved.