Synergistic modification of glucomannan by deacetylation-esterification for improved foam characteristics

Foaming agents derived from natural polysaccharides provide environmentally friendly alternatives to synthetic surfactants, but their native foaming performance is often limited. This study aimed to improve the foaming properties of glucomannan through a combined deacetylation-esterification modification to enhance amphiphilicity and foam stability. Deacetylation using Na₂CO₃ in 75% ethanol achieved a degree of deacetylation of 84.06%, enabling effective esterification with oleic acid. The modified glucomannan reached a maximum degree of substitution of 0.330 at a 1:4 w/v ratio and 240 min reaction time. FTIR confirmed ester bond formation and hydrophobic chain incorporation. Increasing substitution decreased water absorption, solubility, and surface tension, while viscosity, molecular weight, and critical micelle concentration increased. The highest foaming capacity and stability occurred at 3% w/v, showing low density and extended foam half-time, with bubble sizes ranging from 3.82 ± 0.82 to 81.35 ± 21.48 μm. These findings highlight modified glucomannan potential as a bio-based foaming agent.