The three stages of the Maillard reaction are Early, Advanced, and Final. In the early stage coffee bean color remains unchanged and does not absorb any U/V light. Sugar-Amine condensation and Amadori rearrangement reactions take place. In the advanced stage the color may yellow with as UV absorption kicks in. Sugar starts to degrade and fragment. In the final stage coffee beans move from yellowish to brown, condensation of aldols and sugars occur along with the formation of new chemical compounds. The sum total of this reaction is the production of Melanoidins, which are compounds developed from the destruction of sugars and proteins during the process.