Glasses Tech

September 22, 2009

The effect of phase transitions on release of n-propanol entrapped in carbohydrate glasses

Filed under: Glasses 1995 — admin @ 5:58 am


The mobility of an organic volatile probe (1-n-propanol), incorporated in two types of amorphous carbohydrate glasses, was evaluated by measuring probe retention as a function of time. Retention was found to depend on temperature, moisture content and the degree of matrix collapse. In sucrose glasses, crystallization and probe release occur simultaneously and both crystallization and release depend on the temperature above Tg, as predicted by the William-Landel-Ferry (WLF) equation. In sucrose: raffinose systems held above Tg, initial rapid release of the probe (`fast′; release) is observed, coinciding with, and presumably due to, matrix flow during collapse, followed by a much slower diffusional release. Relaxation times for collapse (τc), and `fast′; release (τfr) above Tg were calculated. They were found to be dependent on T-Tg and moisture content. Dependence of relaxation times on (T-Tg) was found to be well predicted by the WLF equation.

Guy Levi and Marcus Karel
Department of Food Science and Center for Advanced Food Technology, Rutgers University, PO Box 231, New Brunswick, New Jersey 08903-0231, USA

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