APPLICATION OF THE WLF EQUATION TO DESCRIBE THE COMBINED EFFECTS OF MOISTURE AND TEMPERATURE ON NONENZYMATIC BROWNING RATES IN FOOD SYSTEMS

Nonenzymatic browning rates of several vegetables, dairy products and model food systems stored at different moisture contents and temperatu res were analyzed and related to their glass transition temperature (T (g)). The data analyzed corresponded to a region of moisture content i n which effects due to reactant diffusion could be expected. As change s in diffusion constants may in turn, be related to glass transition, the Williams-Landel-Ferry (1955) (WLF) equation was used to describe t he combined effects of moisture and temperature on the nonenzymatic br owning rate constants. Ferry's (1980) procedure of reduced variables u tilizing a reference temperature (T0) was applied, the T0 selected wit hin the experimental range. In this procedure, the equation coefficien ts are calculated for the equation using T0. Then they are recalculate d by shifting the selected reference temperature to T(g) to obtain the coefficients with reference to T(g). The resulting equation can be ap plied to relate the browning rate constants to temperature, moisture a nd T(g). The equation has predictive value and the method avoids extra polations when data at T(g) are not available.