Kinetics of heat-induced browning in concentrated milk with sucrose as affected by pH and temperature / Cinética del pardeamiento inducido por calor en sistemas de leche concentrada con alto contenido de sacarosa. Influencia del pH y de la temperatura

A model system constituted by whole dry milk powder, sucrose, and distilled water was used to establish kinetic parameters of the heat-induced browning process (HIBP). Second-order central com posite design was chosen with pH and temperature as selected variables. Color response was the Kubelka-Munk index (K/S) calculated from reflectance colorimetric measures as a function of time using the self-backing reflectance transformation (SBRT) procedure. Results showed that HIBP pseudo- order reactions were variable between 0 and 0.6. Reaction rate coefficient (k) was strongly dependent on pH and temperature. In general, k increased as both pH and temperature increased but the influ ence of temperature was higher than that of pH. Q 10 was dependent on temperature, ranging be tween 2.15 at 130-140 °C and 2.44 at 100-110 °C, whatever the pH. k values were analyzed with the Arrhenius expression. Values of E a , calculated for different pH, were coincident (25.34 kcal/M).