Application of the synthetic polymer approach to the glass transition of fruit leathers

A commercial fruit leather was analysed in an effort to document the application of the synthetic polymer approach to its vitrification properties. Techniques employed were dynamic mechanical thermal analysis on tension and modulated differential scanning calorimetry. The temperature and frequency dependence of Young’s modulus were utilized in the construction of composite curves of viscoelasticity that identified the rubbery plateau, glass transition region and glassy state. The painstaking investigation of viscoelasticity supported by the combined framework of WLF/free-volume theory was successful in identifying the mechanical Tg of the partially vitreous material at subzero temperatures. That was contrasted with the corresponding value obtained using calorimetry, and the nature of the discrepancy between the two estimates of Tg was discussed.