the labels are filled with gelatine. gelatine is a natural substance and reacts to factors such as temperature, oxygen and sunlight in the same way as food, and if attached to fresh food as a sealed label, it mimics the food&rsquos process of decay. when the product inside the packaging is fresh, the gelatine in the label stays solid.but as the food starts to go off, the gelatine breaks down and becomes a liquid, making the label bumpy.small and triangular in design, the bioreactive bump mark is designed to be stuck on to the packaging at the time the food is packaged. bump mark is made up of four layers a bumpy sheet of plastic is covered by a squidgy layer of gelatine and sandwiched between two sealing layers of plastic film.