What is the purpose of the reagent blank in the K-TSTA assay?

The reagent blank is required to show that the GOPOD reagents are working as expected. All absorbances including samples and glucose standards and control flours should be read against the reagent blank.

It can be also used to determine whether the sample has a high glucose content and if ethanol washing is necessary.

This can be achieved by analysing a sample blank. Instead of adding enzymes, add buffer at these incubation steps and then measure by GOPOD. 

If the glucose content is high (a high absorbance is seen), we would recommend that you include the ethanol washing steps by following method (E) on page 13 of the data booklet.