EXTENT OF NONENZYMATIC BROWNING IN GRAPEFRUIT JUICE DURING THERMAL AND CONCENTRATION PROCESSES: KINETICS AND PREDICTION

The kinetics of browning in grapefruit juice during thermal and concentration processes was studied. The reaction is seen to be initially slow (lag period) and later relatively rapid (post‐lag period), represented by an exponential and a linear time function respectively. The effect of temperature on the rate of reaction obeys the Arrhenius equation. The activation energy, for a solids content of 11 to 62° Bx, ranges from 8 to 30 Kcal/mole in the lag period and from 15 to 24 Kcal/mole in the post‐lag period. Curve‐fitting techniques yielded an empirical kinetic equation correlating the rate of reaction with temperature and degree of concentration; this equation in turn yielded a mathematical prediction model, used to advantage in studying the extent of browning in grapefruit juice during commercial thermal and concentration processes.