Plant peroxidases, proteins that contain heme and catalyze the oxidation of organic compounds by hydrogen peroxide, can interfere with tests for blood or hemoglobin. heating samples to 100 oc for 20 minutes can deactivate plant peroxidases. why should one not be surprised that these plant enzymes could interfere with tests for blood?

Blood is an amalgamation of various chemicals, so it would be not practical to test for each one of them. Thus, the majority of the tests for blood are actually testing for a solitary component, that is, heme, as blood comprises of an ample amount of heme and so it is comparatively easy to determine.

However, the plant peroxidases also comprise heme, thus, the blood test, which is actually a heme test, will come positive. This leads to an outcome known as false positive. Thus, in the case of forensics, one has to depend on other things also to prove the suspect's guilt or innocence.