Effect of irradiation treated Gum Tragacanth on physical stability of oil in water emulsions in acidic condition
چکیده
Background: A wide variety of food, pharmaceutical, cosmetic products are constituted of emulsions, which have a great importance in many industries such as food industry due to physical and rheological properties. But, the main limitation of these systems is thermodynamically unstable which caused phase separation during storage time. According to previous studies, Astragalus Gossypinus species of gum tragacanth are able to reduce the interfacial tension of the oil in water system and stabilize oil in water emulsions.Today; irradiation is used to disinfect many polymers. In this study we assessed the effect of Gum tragacants irradiation treatment of oil in water (10% wt) emulsion in acidic condition were determined.
Materials and Methods: In this way, the creaming index was measured to investigate the effect of gum tragacants irradiation treatment at doses of 0, 1/5, 3kGy on stability of oil in water emulsions which contain 0.5% w/w gum tragacanth and 10% w/w sun flower oil, in different pH (2.5, 4, 5.4) during 30 days storage at 25° C. To understand the mechanism of stabilization, steady and unsteady rheological properties and particle size distribution parameters were measured. Rheological properties were measured by using rheometer and particle size distribution was determined using laser diffractometry.
Results: According to the data, the samples of irradiated gum up to a dose of 1.5 and 3, at pH of 5.4 and 4 were completely stable for 30 days. The results showed irradiation treatment had significant influence on the particle size distribution. Irradiation treatment at a dose of 1.5 and 3 kGy reduced particle size distributing parameters. However, irradiation treatment at 1.5 kGy was most effective on the reducing of particle size distribution parameters. pH had no significant effect on the particle size distribution parameters. Also, irradiation affected the stability of emulsions by changing rheological properties. The amount of these changes depended on the irradiation dose.
Conclusion: We observed irradiation treatment with 1.5 kGy reduced the particle size distribution parameters to a certain extent and also with changing of the rheological properties of system caused a more stable system compared to those with 3 kGy treatment. Lower pH by changing the gum conformation and effect on the rheological properties resulted in reduced stability; accordingly we observed that the most unstable system was the system which contains gum tragacanth was irradiated with 3 kGy at pH of 2.5.
Key words: oil in water emulsion, stability, gum tragacanth, irradiation, pH