Samples were taken at 0, 0.5, 1.0, 3.0 and 5.0 h and the reaction mixture was rapidly heated in a
boiling water bath for 30 min to inactivate the enzyme. The inactivated samples were submitted to
an extraction procedure according to Shore (1971) and histamine was quantified by a spectrofluorimetric method based on the reaction of histamine with o-phthalaldehyde (Shore, 1971).