Papain enzyme is isolated from the latex of the Carica papaya plant. Suitable sources of
this enzyme included Pfaltz & Bauer (item #PO1100) and Sigma Chemical (catalog
#P-3375). Methyl isobutyl ketone, concentrated hydrochloric acid (36-37%), and
sodium sulfite were reagent-grade available from any bulk supplier.
Kimble 4.0-dram vials (catalog #60957) with polyethylene protected caps were used
for the sample preparation, and extraction was completed with 5-ml plastic transfer
pipets (Fisher catalog # 13-711-9A)