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

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.
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.
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.
As three samples of Zedo gum had different characteristics, colour can be a good tool in trade.