2.5.2. Enzyme sensor evaluation
DAO catalyses the oxidative deamination of amines and diamines
to the corresponding aldehydes and ammonia accompanied
by a reduction of molecular oxygen to hydrogen peroxide, as
follows:
Once either the standard or the meat extract is injected into the enzyme
sensor, the reaction takes place and the current decreases by
the oxygen consumption, in a proportional way to the amine
content.
The operational stability was tested by successive injections of
histamine standard (0.01 mg/mL) along 2 days. For the storage stability,
10 DAO membranes were stored in sodium phosphate buffer
(100 mM, pH 7.2) at 4 C. One DAO membrane per week was tested
with the histamine standard (0.01 mg/mL) per triplicate.
The repeatability of the analysis was tested by repeated injections
of the same histamine standard and of a fermented sausage extract
(42 days of curing), which were all analysed on the same day
with the same equipment under the same operating conditions.