Peroxidase test

a) Solutions. In order to check the peroxidase activity two solutions have to be prepared:

1% guaiacol in alcohol solution (1 g guaiacol is dissolved in about 50 cm³ of 96% ethylic alcohol and then this preparation is brought to 100 cm° with the same solvent);

peroxide solution 0.3% (1 cm³ perhydrol is brought to 100 cm³ with distilled water.

b) Sampling. From various parts of the material samples are taken (about 20-30 pieces, etc.); the material is then crushed in a laboratory bowl in order to obtain an average sample.

c) Check. Prom the average sample, 10-20 g of material is taken in a medium capacity test tube; on this sample are poured: 20 cm³ distilled water; 1 cm³ of 1% guaiacol solution; 1.6 cm³ of peroxide solution.

The contents of the test tube is shaken well. The gradual appearance of a weak pink colour indicates an incomplete peroxidase inactivation - reaction slightly positive. If there are no tissue colour modifications after 5 minutes, the reaction is negative and the enzymes have been inactivated.

As an orientative check it is also possible to simply pour a few drops of 1% guaiacol solution and 0.3% peroxide solution directly on blanched and crushed vegetables. A rapid and intensive brown-reddish tissue colouring indicates a high peroxidase activity (positive reaction).