Application of different thermal and non-thermal methods for removal of tannin from Persian gum

Persian gum is an Iranian native gum which obtains from the trunk and branches of wild almond tree. This gum is found in different colors and there is a direct relation between its color and tannin content: darker the color, higher the amount of tannin. Since the bioavailability of proteins and minerals is limited by tannins, they are known as anti-nutrient compounds; hence, it is essential to remove tannin from Persian gum in order to increase its quality and amount of utilization in the food industry. Thereupon, tannin removal from Persian gum using different thermal and non-thermal methods was the main aim of this research. In this regard, soaking either in water or saline solutions (mono- and divalent salts) was considered as non-thermal method. On the other hand, autoclaving (121 ̊C for 20 min) and boiling (5, 10 and 15 min) were applied as thermal methods for tannin removal of Persian gum which was categorized based on color: white, yellow and brownish. As well, weight reduction of gum granules and rheological properties were investigated after tannin removal. According to the results, the highest tannin removal was observed in the case of brownish Persian gum and the most yield of tannin removal belonged to soaking in water for 180 min (75.67 ± 0.25 %), using CaCl2 solution at the concentration of 1% (w/w) (74.32 ± 0.54 %) and boiling for 15 min (67.08 ± 0.19 %), respectively (p < 0.05). Based on rheological analysis, apparent viscosity of samples after soaking either in water or CaCl2 solution as well as boiling, the treatments which had the highest tannin removal yield, was higher than control sample. However, the suitable rheological model for control and the treated gums was Herschel-Bulkley, indicating that type of flow behavior did not been affected by tannin removal.