Figure 2. Titration curve of pineapple extract. 10 mL of the extract prepared as in Preparation of pineapple extract given in the text was acidified with HCl to pH 2.95, 0.1 mL aliquots of 0.1 M NaOH were added under constant stirring, and pH was determined before and after each addition of alkali at 30ºC.