Extraction and camparison of amount of pectin, degree of estrification and galacturonic acid content in some citrus fruit peels

Background and Pectin is widely used in food, cosmetic and drug industries. Because of high production and consumption of citrus fruits in Mazandaran, fruit peel is available in large quantities. The objective of the current investigation was to determine the amount of pectin, degree of estrification, a key factor in rheological properties of pectin, and galacturonic acid content as a criterion for pectin purity. Thirteen species of commonly used citrus fruits, orange cultivates (Citrus sinensis Washington navel, Sanguinello, Valencia, Acidless, Moro, Shahsavari, Italian orange), Clementine, Unshiu, Grapefruit (C. paradisi), Bitter (sour) orange (C. aurantium), Lemon (C. limon) and Tangelo were collected at the ripening stage. All the trees were cultivated in the experimental fields, Fajr citrus experimental institute. Amount of pectin was determined by acidic extraction from dry albedos of fruits. Degree of estrification and galacturonic acid content were determined by USP standard titrimetric procedure. The highest amount of pectin was found in Italian orange (27%), Shahsavari orange (25%) and Sanguinello (20 %) on the basis of dry weight. The highest degree of estrification (11.5%, 10.9% and 9.6%) was found in Lemon, Washington navel and Bitter (sour) orange respectively. The highest galacturonic acid contents were found in Washington navel, Lemon and Italian orange (89.3, 85.4 and 77.7 respectively). Six fruits were suitable for utilization in drug industries including: Washington navel, Acidless, Shahsavari, Italian orange, Bitter (sour) orange (C. aurantium), Lemon (C. limon). Washington navel and Lemon had the most suitable pectin for pharmaceutical purposes.