Figure 5. Thermal stability behaviour of the proteinase activity in the pineapple extract in the absence (O-O-O) and presence (Δ-Δ-Δ) of 9.8 mM sodium carbonate. 1.0 mL aliquots of the pineapple extract were incubated for 30 min at different designated temperatures, cooled in ice for 5 min, brought to and maintained at 30ºC, and the proteinase activity was assayed as in Proteinase assay given in the text.