The physicochemical property characterization of agar acetate

• The DS dependence of physicochemical properties of agar acetates was studied.
• The gel microstructures of agar and agar acetate were characterized by Cyro-SEM.
• Verified that the water holding capacity of agar was increased after acetylation.
• Verified that the thermal stability of agar was lowered after acetylation.

A series of agar acetates with different degree of substitution (DS) were prepared, and their properties were determined and analyzed. The results showed that the gelling temperature, the gel melting temperature, the gel strength, the gel hardness, the gel fracturability, the gel springiness and the solution apparent viscosity of agar acetates all decreased except that their gel cohesiveness increased with the increase of DS. The variation process of agar molecules in solution from coil to helix could be also observed by measuring solution optical rotation in a lower concentration at which even the solution could not form a gel. The gel skeleton structures of agar acetates were of porous network structures, and the pores became smaller and denser with the increase of DS. After acetylation, the water holding capacity of the agar was improved, but its thermal stability was lowered.