Submitted to: Proceedings of Florida State Horticultural Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/19/2008
Publication Date: 4/1/2009
Citation: Luzio, G.A. 2008. Microwave release of pectin from orange peel albedo using a closed vessel reactor system. Proceedings of Florida State Horticultural Society. 121:315-319. Interpretive Summary: After removal of soluble sugars and other compounds by washing, citrus peel is largely composed of pectin, cellulose and hemicellulose. In order to utilize the greatest amount of citrus peel byproduct, it would appear reasonable that one or all three of these polysaccharides be converted into a useful industrial material. One of the components, pectin is relatively easy to modify using enzymes and has great utility in the food industry and other applications. Thus it appears reasonable to focus on the use of pectin for the maximum utilization of fruit peel for new products from peel. Modification and use of pectin in many applications requires the pectin to be a soluble form. Pectin is normally extracted using heat and strong acid conditions at 70 °C. New microwave technology was presented which allowed for rapid heating and cooling of the extract to temperatures in excess of 100 °C. The quality and amount of pectin extracted using microwaves at 115 °C was equivalent to that extracted under at 70 °C using resistive heating except the extraction was performed 100 times faster. This data is important for the future development of a cost effective process for pectin extraction for industrial applications.
Technical Abstract: Pectin was extracted from blood Moro orange in a closed vessel reactor heated with microwave irradiation. Time of heating was either 2 minutes at 110 °C or 210 minutes at 75 °C in pH range of 1.7 to 2.8. The run at 75 °C and a pH 1.7 with resistive heating was performed to simulate industrial process conditions. The highest recovery of pectin (anhydrogalacturonic acid (AGA) of 3.44 mg/mL) was observed at 110 °C and pH 1.7 with microwave heating but the degree of methylation (DM) under these conditions was at the lowest level at 50.3%. A DM of 72.7% was observed at 110 °C and pH 2.8 but the pectin yield was lower at an AGA value of 2.15 mg/ml. At pH 2.2 both the DM and AGA value was intermediate between the other two reactions suggesting that lower pH improves yield but at the expense of a lower DM value. MW changes were observed with the various heating and pH values, but the largest effects were on AGA recovery and DM. The data suggests that by careful selection of pH and temperature acceptable yields of pectin using microwave heating can be obtained while preserving a significant portion of the DM.