Some Physicochemical and Rheological Properties of Zedo (Farsi) Gum Exudates from Amygdalus scoparia

Background and Objectives: Zedo gum is exuded in three colours (white, yellow, and red) from Amygdalus scoparia. It is used in both food and non-food industries, as well as in traditional medicine. This study aimed to determine the physicochemical and rheological properties of Zedo gum. Materials and Methods: Zedo gum was collected in Sirjan and classified into three groups, based on colour (samples W, Y, and R). Their soluble parts were separated by centrifuging the dispersions and freeze-drying the supernatants. Surface tension was determined using Du Nouy ring method and NMR spectroscopy was carried out using a Varian Inova-500 MHz spectrometer. Gel Permeation chromatography was used for determining molecular weight and rheological data were obtained with a Physica MCR 301 rheometer. Results: Surface tension decreased as the concentration decreased, except for sample R that had a maximum point at 1 %. The molecular weight of sample W was the highest, while its dispersity was the lowest. NMR spectroscopy indicated that Ara residues variously were  linked to α-Araf residues, and Gal residues were determined as terminal α-Gal residues. Intrinsic viscosity values for samples W, Y, and R were 7.14±0.13, 6.45±0.11 and 5.40±0.15dl/gr, respectively. Rheological results showed that viscosity was inversely proportional to temperature and directly to concentration. Conclusions: As three samples of Zedo gum had different characteristics, colour can be a good tool in trade. Keywords: Zedo, Dispersity, GPC, Amygdalus Scoparia, NMR