The capacities of added sucrose, glucose, invert sugar and glycerol to decrease water activity (aw) of guava pulp (15° Brix) were compared. Added fosforic, citric and lactic acids were also assessed for their effects in pH reduction as well as in increasing titritable acidity in pulp. Theoretical, experimental and calculated aw values were compared as a function of solute addition. Norrish model was used to determine theoretical aw values and Ross equation to generate calculated aw values using experimental ones. Acidity and pH curves were determined according to titrimetric and potentiometric assays, respectively. Glycerol exhibited the strongest capacity regarding aw reduction, followed by glucose, sucrose and invert sugar. In concentrations up to 1% w/w, all tested acids showed similar effects in decreasing pH and increasing titritable acidity of guava pulp.
guava pulp; water activity; titritable acidity; pH
