Ascorbic acid is known to be thermolabile. To date
several authors have studied its thermal degradation
kinetics in citric juices under pasteurization conditions
and stated that it follows a ®rst order reaction model
(Table 1) (Johnson, Braddock & Chen 1995; Saguy,
Kopelman & Mizrah, 1978). Alvarado and Viteri (1989)
studied the degradation of total vitamin C in citric fruits
for an extended time range (up to 150 min at a temperature
of 60°C) and concluded also that the reaction
was ®rst order, (Table 1). No studies were published so
far on the pattern that ascorbic acid (AA) degradation
follows when the time range is extended far beyond the
practical range under pasteurization conditions.