Carotenoids are the compounds responsible for yellow, orange and red colours in many fruit, vegetable and algal sources. Within each source, carotenoids vary in concentration, proportions and chemical structure, all of which influence how it can be used in a food product.
When heat is added to a substance, the molecules and atoms vibrate faster. As atoms vibrate faster, the space between atoms increases. The motion and spacing of the particles determines the state of matter of the substance. The end result of increased molecular motion is that the object expands and takes up more space.
Most matter increases in volume when it gets hotter. For example, if an iron rod is heated, it will get longer and fatter and its density will decrease. This happens because the mass of the rod stays the same, but its volume increases.