Non-enzymatic browning in peach puree during heating

Non-enzymatic browning in peach puree (11 degrees Brix) due to extended thermal treatment was investigated. Absorbance at 420 nm, colorimetric parameters (CIE L*, a*, b* and Delta E*), content in sugars (fructose, glucose and sucrose) and hydroxymethylfurfural were used to estimate the extent of nonenzymatic browning during heating at high temperatures (80, 85, 90, 95 and 98 degrees C) for 480 min. Zero and first order kinetics were applied to describe evolution of relative absorbance at 420 nm. Relative luminosity and sucrose content follow a first order kinetic. Colour difference was successfully adjusted to a model including two stages: the first one includes the colour formation and it follows a kinetic of order zero and the second includes the colour destruction and it follows a first order kinetic model. Both first and autocatalytical models can describe HMF formation. Parameter b* was significantly reduced with heating time, especially at higher temperatures, on the contrary parameter a* increases during heating. The Arrhenius model described well the temperature dependence of the reaction rate constant for all the parameters considered. (C) 1999 Canadian Institute of Food Science and Technology. Published by Elsevier Science Ltd. All rights reserved.