How can i detect Formalin in food easily
Simple commercially available tests contain formaldehyde dehydrogenase. This enzyme selectively catalyzes the chemical reaction of formaldehyde:

$$\ce{CH2O + NAD+ + H2O -&gt; HCOO- + NADH + H+}$$

The enzymatic reaction is typically indicated by reduction of a tetrazolium salt to a coloured formazan dye.