Extraction of Pectin Polysaccharide from Walnut Heartwood and Evaluation of Its Yield and Physicochemical Properties

Walnut is one of the most important and valuable agricultural products in the country. The aim of this study was to investigate the effects of three variables of pH values (1, 1.5 and 2), extraction temperatures (60, 70 and 80°C) and process times (60, 90 and 120 min) on yield, degree of esterification and galacturonic acid of pectin extracted from heartwood waste of walnut using response surface statistical method. Based on the results, optimum conditions for pectin extraction with the highest extraction yield (14.32%), degree of esterification (64.03%) and galacturonic acid (63.62 %) were associated with pH 1.68, process temperature of 80°C and extraction time of 120 min. Total ash, molecular weight, emulsifier, rheological and Fourier transform infrared spectroscopy assessments were carried out on pectin optimum sample. The results showed the total ash was 14.1% and MW of pectin optimum sample was 35.61 kDa. This sample, with suitable emulsifier properties, showed pseudoplastic behavior and its FTIR spectroscopy diagram was rich in galacturonic acid.