INFLUENCE OF SYSTEM COMPOSITION ON ASCORBIC-ACID DESTRUCTION AT PROCESSING TEMPERATURES

The anaerobic L-ascorbic acid (AAs) destruction in glucose aqueous mod el systems (water activity, a(W), 0.94) of pH 3.5, 4.1 and 5.0 was stu died. The AAs degraded as a function of time and temperature (70, 80 a nd 90 degrees C) with a behaviour that, in general, could be described by first order kinetics except for AAs in the system containing L-lys ine, in which the results adjusted to zero order. The increment of pH from 3.5 to 5.0 accelerated AAs destruction and browning reactions. Th e addition of tin(II) or lysine to the glucose medium, increased AAs l oss and browning. No difference was observed in AAs degradation and co lour intensity when sorbic or propionic acid were used as antimycotics , at pK 3.5. Packaging the glucose system of acid pH with an air chamb er, produced a faster destruction of AAs and browning of the solution than the one observed for the same system in anaerobic condition. In a erobic condition, the presence of glucose produced a lesser degradatio n of AAs than the one observed in the system without humectants.