Phosphate crosslinking of gum Arabic with sodium trimetaphosphate as a sustainable biopolymer

Gum Arabic (GA), a natural biopolymer, is highly hydrophilic and mechanically unstable, limiting some applications. This study investigates modification of GA using sodium trimetaphosphate (STMP) and changes in its physicochemical and thermal properties. A custom factorial design assessed STMP concentration (2 %, 5 %, and 8 %), pH (10, 11.5, and 13), and temperature (30, 40, and 50 °C), with viscosity and water absorption as responses. Analysis of variance (ANOVA) yielded an R2 of 0.7519 for the viscosity model and 0.5006 for water absorption. Conditions selected for viscosity were 8 % STMP, pH 13, and 40 °C, producing 4.56 cP (predicted: 4.601 cP) against a maximum of 6.25 cP. Conditions selected for water absorption were 2 % STMP, pH 11.5, and 40 °C, producing 17.85 % (predicted: 12.47 %) against a maximum of 32.57 %. Fourier transform infrared spectroscopy (FTIR) indicated phosphorylation and hydroxyl substitution through P--O--C and P=O stretching vibrations at 976 and 1256 cm−1, respectively. Thermogravimetric analysis (TGA) showed improved thermal stability in the viscosity-optimised sample, with a peak degradation temperature of 382 °C, degradation weight loss of 72.89 %, and residual mass of 23.47 %. This sample showed the most pronounced chemical modification and greatest thermal stability. STMP-crosslinked GA may serve as a sustainable, locally available biopolymer for concrete admixtures, drug-delivery encapsulation, and beverage stabilisers.