What is ribose

Browning in canned fish is commonly associated with ribose. Undesirable colour changes in shellfish during canning often involve metal  ions, for example, the blue discoloration of crab meat involves iron, whereas a black discoloration in prawns relates to copper content. Eels, abalone and albacore tuna; all undergo discoloration on processing, due to the high iron content of the raw material. Discoloration of this type is increased when the material is held in frozen storage prior to canning, because of the build-up of free sulphur in the tissue. Iron and free sulphur react together during heat processing, precipitating black iron sulphide on the sides of the container, in the fish itself and especially in any free liquid.