Onion and garlic are two important vegetables in the world, which are processed in various forms such as powder, puree, and minced paste. During processing, discoloration is a major concern because it limits commercial utilization. Recently, the mechanism of the discoloration has gained a particular scientific interest, and a great progress has been made in this field. It is concluded that a greater knowledge of these areas would lend to the development of more efficient methods of controlling the discoloration. Future outlooks are highlighted with the aim to suggest a research line to follow for further studies.