The effect of pH on TPA was assessed to contribute with the
discussion on the differences found in the clarification assays
(Fig. 4). In the laboratorial extracts TE1 and TE2, TPA superior
activity occurred at pH 4.0. When the reaction was performed at
pH 3.0, enzymatic activity was practically identical for TE1,
whereas TE2 presented a decrease of 35% in enzymatic activity. In
pH values above 4.0, a continuous decrease in pectinolytic activity
was observed in both experimental extracts. In the commercial
preparations, higher activities were observed at pH 5.0, with
a decrease at bigger or smaller pH values. By comparing the
natural pH of juices (Table 2) with the best pH values found in TPA
assays, coherent responses were found in clarification assays
performed with TE1 and TE2, but not in those with the commer-
cial preparations PC and PB. Thus, it can be concluded that other
factors, such as the juice chemical composition and the presence
of other enzymes apart from pectinases in the enzymatic
complexes in test, could interfere significantly on the clarification
process