Pectin Extraction from Lemon By-Product with Acidified Date Juice: Effect of Extraction Conditions on Chemical Composition of Pectins

Mixtures of date and lemon pectins were extracted from lemon by-product with acidified date juice under different conditions of temperature, pH and time. Individual pectins from date and lemon, respectively, were also extracted using the same experimental conditions, then analysed and compared to pectin mixtures. It was found that the use of extreme conditions resulted in higher galacturonic acid content, lower degree of methylation, lower neutral sugar content, lower molecular weight and darker colour pectins. Examination of the individual neutral sugars showed that the main ones were galactose (1.6–5.4%), arabinose (1.6–4.2%) and rhamnose (0.5–0.8%). The Gal A/Rha molar ratios varied from ∼53 to ∼149. Moreover, mixture of pectin extracted at the optimal extraction conditions (84.34 °C, pH 2.8 during 3 h 34 min) had interesting properties, with a high galacturonic acid content (63.4%), low degree of methylation (∼35%) and a mass molecular weight of about 243 kg/mol.