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.
If the kinetic energies of the molecules go up, then the heat (energy) within the gas has gone up. Therefore, we see an input of heat can cause an increase in temperature because the input of heat is realized as an increase in the kinetic energies of the gas molecules.