Carboxymethylation of frankincense gum and investigation of viscosity and colorimetric indices

Frankincense is a resinous gum obtained from some species of the Boswellia genus. The use of frankincense for food and medicinal uses dates back to more than five thousand years ago, but despite its importance and application, only 27-35% of it is soluble in water. As most frankincense gum is insoluble, this research used the response surface method to study the effect of different chemical modification conditions (NaOH concentrations (X1), reaction temperatures (X2), and MCA concentrations (X3)) on increasing the solubility percentage. The results of the optimization process of the chemical modification of frankincense gum indicate that the conditions of maximum solubility are equal to 85.49, with a desirability rate of 0.97. Therefore, the concentration of NaOH and MCA equal to 0.048, 0.01 mol, and a temperature of 75 degrees Celsius chose as the best optimization conditions. In addition, the intrinsic viscosity and molecular weight of the native gum were higher than the modified gum under optimal conditions. There is a significant difference between the apparent viscosity of natural gum (18.02 ± 0.726 mPa.s) and modified (17.36 ± 0.681 mPa.s) (p>0.05). The results indicate that native and modified gum in optimal conditions show a shear thinning behavior with increasing shear rate, and their behavior is similar to pseudoplastic. The colorimetric test with image J software indicated that carboxymethylation of frankincense gum led to significant changes (P < 0.05) in the total color difference factor (ΔE) and whiteness index (WI), L*, a*, and b*factor.