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The effects of adding one of the species of Iranian gum tragacanth, Astragalus compactus, to maltodextrin solutions used for microencapsulation of 2-methylbutyl acetate (water-soluble flavoring compound of strawberry) were studied. Initial emulsions were evaluated regarding rheological behavior and particle size distribution. The resulted microcapsules were also analyzed for particle size distributions, glass transition temperature Tg, the morphology of the capsules and the rate of release from them. The results showed that addition of 0.5% w/w A. compactus gum to maltodextrin solutions (14.5% w/w) can increase the viscosity and Tg to an optimum level and can prevent stickiness. Also this species of gum tragacanth had an interesting effect in reducing physical defects of microcapsules and eliminated ruptures significantly. It was also showed that the rate of release of 2-methylbutyl acetate decreased by incorporating gum tragacanth in the wall material. Practical Applications Microencapsulation is of great interest in preservation of flavoring compounds. One of the most important wall materials is maltodextrin, which has several defects to protect flavorings. This study proposes the use of a new material, Iranian gum tragacanth from Astragalus compactus, to overcome these defects. It was found that new microcapsules did not undergo rupture and could retain the flavoring well. [ABSTRACT FROM AUTHOR]

Dispersions of different species of gum tragacanth were sonicated at a frequency of 24 kHz with a total nominal output power of 200 W for different time intervals (0, 7, 15, 45 and 90 s). Various species behave differently under sonication, which is related to structural differences in these species. In the case of Astragaslus compactus and A. rahensus dispersions, as the sonication time increased, the viscosity and particle size of the dispersions decreased, just as in gum Arabic solutions. However, A. gossypinus gum behaved differently compared to the other species. At early stages of sonication (up to 15 s), the viscosity of the dispersions increased sharply and reached its maximum value (106.04 mPa s) as the particle size increased slightly to 275.69 μm. Continuing sonication led to a decrease in the viscosity of the dispersions, though the particle size did not show any changes. This behaviour is thought to be due to the rupture and aggregation of particles. [ABSTRACT FROM AUTHOR]