Colour, sugars and HMF evolution during thermal treatment of apple juice

Non-enzymatic browning in an 11 degrees Brix apple juice during thermal treatment was studied through changes in colour by colorimetric parameters (A(420), colour difference and index of browning), and HMF and sugars (fructose, glucose and sucrose) evolution. Zero and first order kinetics were applied to describe evolution of colorimetric parameters. The formation of HMF was fitted to autocatalytical and first order equations. Sucrose tends to disappear according to a first order kinetics giving fructose and glucose. For the reducing sugars (fructose and glucose), no clear tendency was observed. The effect of temperature can be described by an Arrhenius-type equation.