Microwave Release of Pectin from Orange Peel Albedo Using a Closed Vessel

摘要

Pectin was extracted from Moro blood 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 at pH values of 1.7 to 2.8. A run at 75 °C and at pH 1.7 with resistiveheating was additionally performed to simulate industrial process conditions. The highest recovery of pectin [anhydrogalacturonic acid (AGA) of 3.44 milligram per milliliter] was observed at 110 °C and pH 1.7 with microwave heating but the degree of methylation (DM) under these conditions was the lowest at 50.3 percent. A DM of 72.7 percent was observed at 110 °C and pH 2.8, but the pectin concentration was lower at an AGA value of 2.08 mg per milliliter. At pH 2.2 both the DM and AGA values were intermediate between the other two reaction conditions suggesting that lower pH improves yield but at the expense of a lower DM value. Molecular weight 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.