Sugar colourants, that is, coloured compounds associated to cane sucrose or formed during sugar processing, although being a small fraction of sugar impurities, are of great importance on an consumer point of view.
Inside the cane stalk, sucrose is colorless, but during production and refining there is formation of coloured compounds which gives a colourization to the final sugar produced. These compounds can be:
- derived from cane natural colourants;
- originated from reactions involving sugars.
Sugar colourants may present a strong dark colour, as in melamine, or light colours as with some phenols. Other compounds being not coloured but contributing for colour formation, as invert sugars, amino compounds and iron compounds, are considered as colour precursors.
Colour and Molecular Weight of Colourants
Colourants from sugar cane
The main sugar cane natural colourants include, mainly, cane pigments and phenolic acids.
Sugar cane pigments
Sugar cane pigments are mostly chlorophylls, carotenes, xanthophylls and flavonoids. The first three pigments are not water soluble, being therefore easily separated during cane juices clarification (Farber and Carpenter, 1972).
As the cane juice Clarification is made in hot and alkaline conditions, anthocianins do not overpass this stage.
Colourants originated by reactions involving sugars
The main sugar colourants originated by reactions involving sugars are formed during extraction and refining processes, and are: HADP (Hexoses Alkaline Degradation Products), melanoidines and caramels.
Colourants through the Process
Bento L.S.M., 2003, technical control of colour in sugar products, Proc. A.V.H. Conf., 22-29
Farber L., Carpenter F.G., Plant pigments as colorants in cane sugar, C.S.S.R.R. Conf., 23-31