Low moisture thermo-mechanical properties of carrot cell wall components

Dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC) were used to measure phase transitions present in carrot cell wall before and after removal of Ca2+ cross-linked pectic polysaccharides, at low moisture (0-20% wet weight basis). A glass transition was detected in the two materials, shifting towards high temperature values with decreasing moisture. Additionally, low temperature relaxations at -50 and 10 degrees C, respectively, were observed and might be assigned to local motions of polysaccharides present in the different cell wall extracts. Stiffness, EY, Of pressed blocks of materials was similar for both carrot cell wall residues. In comparing the thermo-mechanical properties with commercial biopolymers (citrus pectin, cellulose, their mixture and hemicellulose) the different carrot cell wall residues behaved like a pectin dominant material. They also showed a glass transition higher than that of hemicellulose and cellulose. (C) 1998 Elsevier Science B.V.