APPLICATION of the WLF EQUATION to DESCRIBE the COMBINED EFFECTS of MOISTURE and TEMPERATURE ON NONENZYMATIC BROWNING RATES IN FOOD SYSTEMS

Abstract

Nonenzymatic browning rates of several vegetables, dairy products and model food systems stored at different moisture contents and temperatures were analyzed and related to their glass transition temperature (T_g). the data analyzed corresponded to a region of moisture content in which effects due to reactant diffusion could be expected. As changes in diffusion constants may in turn, be related to glass transition, the Williams-Landel-Ferry (1955) (WLF) equation was used to describe the combined effects of moisture and temperature on the nonenzymatic browning rate constants. Ferry's (1980) procedure of reduced variables utilizing a reference temperature (T₀) was applied, the T₀ selected within the experimental range. In this procedure, the equation coefficients are calculated for the equation using T₀. Then they are recalculated by shifting the selected reference temperature to T_g to obtain the coefficients with reference to T_g. the resulting equation can be applied to relate the browning rate constants to temperature, moisture and T_g. the equation has predictive value and the method avoids extrapolations when data at T_g are not available.