The food packaging bag is composed of three separate layers. The inner layer is a porous layer. It is in direct contact with food. If the food is infected with certain bacteria that can cause disease, these bacteria can penetrate the porous layer and reach. The middle layer.
The middle layer contains a nutritious gel that reacts with an antibody in the gel to change color. The bacteria then enters the outermost layer, interacts with another antibody on the surface of the base, spreads out in an X shape, allows the consumer to see it, and knows that the food has gone bad.