biochemistry - How can i detect Formalin in food easily

I am trying to detect formalin in different types of food. Formalin $(\ce{CH2(OH)2})$is an aqueous solution of formaldehyde, which is $\ce{CH2O}$ or $\ce{H2CO}$. I used many chemicals to do this, but every time I fail. Please help me to do this. I got some results in my test by using NFPA 704 and ChEMBL, but that is not enough to save all. I would like to make a simple and easy food formalin detector that can save all the people. Please help me or give me some direction.