ASMAA HAMOUDI KAREEM* AND ETHAR ZAKI NAJI
Directorate of Agriculture in Anbar, Al Anbar, Iraq
*(e-mail : asmaahamodi7@gmail.com, Contact : 00964 79069 83068)
(Received : April 2, 2022; Accepted : April 30, 2022)
ABSTRACT
The study was conducted in the laboratories of the College of Agriculture, Tikrit University. The study
was aimed at studying the chemical properties of pectin extracted from the residues of some plant
sources using citric acid and ammonium oxalate and to estimate the mineral contents. The highest
percentage of pectin yield through citric acid was 64.16, 62.5, 58.33, 45.83, 33.33 and 24.70 for the peels
of eggplant, orange, pomegranate, pomelo, pumpkin and watermelon, respectively. As for extraction with
ammonium oxalate, the percentage of pectin extracted from eggplant peels was 37.45, orange 35.29,
pomegranate 30.58, pomelo 31.76, pumpkin 27.45 and watermelon 20.8. It indicated that the best
extraction solution was citric acid. The estimation of ash content in pectin samples is indicator of
pectin purity. The moisture content was 1.50, 1.75, 5.78, 1.39, 4.16 and 4.89% and ash was 1.88, 2.67,
1.96, 1.65, 2.9, and 4.9%, respectively. The reason for the discrepancy in the ash content of the pectin
extracted from the peels of the samples under study was due to the difference in the extraction conditions
as well as the difference in the type of the primary sample used in the extraction. The equivalent weight
was 849.5, 1744.2, 1052, 612.51, 580.12 and 1250 g, and the methoxyl content was 6.22, 9.72, 6.15, 7.3,
7.44 and 5.39%. The per cent content of anhydronic acid was 55.89, 74.5, 59.14, 66.41, 77.3 and 50.52,
while the degree of esterification was 63.18, 74.07, 59.03, 62.40, 54.64 and 60.57. In conclusion, extraction
with citric acid gave the highest percentages of pectin production from the peels of the studied samples
compared with ammonium oxalate extraction. Further, the nutritional importance of the peels of fruits
and vegetables was confirmed.
Key words : Pectin, moisture, methoxyl, equivalent weight, anhydronic acid