Kinetic models of non-enzymatic browning in apple puree

The effects of thermal treatments on 11∞Brix apple puree were studied at temperatures from 80 to 98∞C. Colour changes (measured by reflectance spectroscopy, colour difference, L*, a* and b* and the evolution of 5-hydroxymethylfurfural (HMF) and sugars (hexoses and sucrose) were used to evaluate non-enzymatic browning. A kinetic model based on a two-stage mechanism was applied to the evolution of colour difference and a*. A first-order kinetic model was applied to L* evolution, while the evolution of absorbance at 420 nm (A420 ) of the liquid fraction was described using a zero-order kinetic model. Thermally treated samples became more reddish and suffered a slight loss of yellow hues. The effect of temperature on the kinetic constants was described by an Arrhenius-type equation. The presence of pulp in the samples led to activation energies for A 420 and sucrose which were lower than those found previously for clarified juices with the same soluble solids content. # 2000 Society of Chemical Industry

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