Anthocianins

A kind of cane flavonoids are the anthocianins. These compounds are responsible for the red, blue and purple colours in plants. In sugar cane the red colour, that can appear in cane surface, is due to these compounds. As anthocianins are coloured at acid conditions and colourless at high pH they have an IV inferior to the unity. These compounds are unstable at neutral or alkaline conditions and are decomposed by heat (Paton, 1992). Heating  anthocianins, at pH 7 , provokes their partial decomposition, with loss of a ring, originating colourless compounds (Smith and Paton, 1985).
The action of sulphites provokes antocianins decolourization, being the colour regenerated through acidification (Smith and Paton,1985).

Anthocianins are located, at higher concentrations, at the cane groing parts. These compounds polimerise rapidly and the juices are more unstable due to their presence (T009 - 1415).

Bibliography

Paton N.H., 1992, The origin of colour in raw sugar, Proc. of Aust.S.S.C.T. Conf., 8-17
Smith P., N.H. Paton, 1985, Sugar cane flavonoids, Sugar Tech. Rev., 12, 117-142