Microwave heating extraction of pectin from lime peel: Characterization and properties compared with the conventional heating method

Microwave and conventional heating methods were used to extract pectin from lime peel waste using different acid extractants (hydrochloric or citric acid) and peel-to-extractant ratios (1: 20 or 1: 40). Hydrochloric acid as the extractant resulted in a higher yield of pectin with both methods. The methoxyl content and galacturonic acid content of lime peel pectin were in the range 8.74-10.51% and 79.29-95.93%, respectively. The intense band around 1730 cm(-1) corresponded to methyl esterified uronic carboxyl groups and confirmed the higher equivalent weight and degree of esterification for the microwave-extracted pectin than that from conventional extraction. Lime peel pectin could be classified as high methoxyl pectin having a rapid-set gel formation. The viscosity and viscoelastic properties of the pectin solution from both heating methods enhanced with increasing solid concentration. Hence, microwave heating can be a short processing time for pectin extraction from lime peel waste with suitable pectin properties.