Mathematical modeling of structural relaxation of selected sugars*

Ratchapong Wungtanagorn** and Shelly J. Schmidt***

The full version of this paper was published in Thermochimica Acta 369 (2001) 95-116. **Bristol-Myers Squibb Company, Regional Office, 10/10-11 Moo 16 Srinakarin Rd., Bangkaew, Bangplee, Samutprakarn 10540, Thailand. ***University of Illinois Department of Food Science and Human Nutrition 905 S. Goodwin Ave. Urbana, IL 61801, USA.

ABSTRACT

Structural relaxation has been intensively studied in polymers. In the past, some mathematical models were proposed in order to describe characteristics of the relaxation. This fundamental research is an attempt to adopt the theory widely used in polymers for biomaterials with further expectation that it can be used to explain systematically some structural relaxation phenomena in complicated biopolymers such as starch. Annealing and physical aging are examples of the structural relaxation phenomena in foods. Structural relaxation of two commonly used sugars (glucose and fructose) and their mixtures has been investigated using standard differential scanning calorimetry (DSC). The characterization of the relaxation process was evaluated through the kinetic parameters of the TNM (Tool, Narayanaswamy, and Moynihan) and Adam-Gibbs models. The evaluation of the relaxation parameters using the curve-fitting method showed similar results for both the TNM and Adam-Gibbs models. Parameter x in both models reflects the relative contributions the temperature and structure dependence of the relaxation times. The higher values of non-linear parameter x for fructose compared to glucose indicate that the temperature dependence of the relaxation time increased in the system. On the other hand, the lower values of the exponential parameter β for fructose show that it has a broader relaxation time distribution spectrum compared to glucose.