The present study introduces the ultrasonic modification of two Iranian native gum exudates, Persian gum (PG) and gum tragacanth (GT) for the first time. They were sonicated at a constant frequency of 20 kHz and temperature of 60 °C for various times (0, 2, 5, 10, 20, 30 and 40 min) and the changes in their molecular properties were investigated using oven drying, gel permeation chromatography-multiangle laser-light scattering (GPC-MALLS), rheometery and FTIR analysis. Results indicated that the soluble dry mass of both hydrocolloids was extensively enhanced (from less than 10% at time zero to more than 90% at the end of treatment time) by sonication. Moreover, the molecular weight and viscosity of gums dispersions was decreased with the increase of the treatment time. Fracture in polysaccharide chains was confirmed by analysis of the molecular weight parameters. Calculation of chain breaks and polydispersity index (PDI) revealed that scissions occurred at the backbone as well as the side branches. PG, owing to its higher molecular weight, displayed more extensive and faster degradation than GT. However, the chain rupture of GT was twice more than that of PG at the end of sonication time. The specific volume for gyration (SV_g) and molecular density (ρ) showed that intact PG contains compactly packed molecules with greater number of cross-linked bonds than GT. Furthermore, the conformational changes into semi-flexible chains and worm-like coils were determined for both gums after 40 min sonication. Variation of the molecular density along with the FTIR analysis demonstrated that ultrasonication broke C-O-C bonds in both PG and GT leading to more flexible chains.

本研究首次介绍了两种伊朗天然树胶渗出液的超声改性，即波斯树胶（PG）和黄tr胶（GT）。将它们在20 kHz恒定频率和60°C的温度下超声处理不同的时间（0、2、5、10、20、30和40分钟），并使用烤箱干燥，凝胶渗透研究其分子性质的变化。色谱-多角度激光散射（GPC-MALLS），流变仪和FTIR分析。结果表明，通过超声处理，两种水胶体的可溶性干物质得到了极大的增强（从零时的小于10％到治疗时间结束时的大于90％）。此外，随着处理时间的增加，树胶分散体的分子量和粘度降低。通过分析分子量参数确认了多糖链中的断裂。链断裂和多分散指数（PDI）的计算表明，在骨架和侧支上均发生了断裂。PG由于其较高的分子量，比GT显示出更广泛和更快的降解。但是，超声处理结束时，GT的链断裂是PG的两倍。回转的比容（SV _g）和分子密度（ρ）表明，完整的PG包含紧密堆积的分子，具有比GT更大数量的交联键。此外，在超声处理40分钟后，确定了两种牙龈的构象变化为半柔性链和蠕虫状线圈。分子密度的变化以及FTIR分析表明，超声处理会破坏PG和GT中的COC键，从而导致更灵活的链。