This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
It has frequently been noticed that in ginger beverages the sugar color disappears, in sarsaparilla and others greatly diminishes in intensity, the shade becoming lighter. Sugar or glucose does not lose all its saccharine character when coloring is prepared, only when turned into sugar-coal; it contains also glucose and levulosan, into which it has been converted by the heat previously to becoming caramel. The metamorphose of converting a solution of cane-sugar into dextrose and levulose, by the aid of the fruit or other acids employed for acidulating the beverages, we have treated already, and refer to it.
The saccharine matter of the coloring, when that metamorphose takes place within the bottle, is doubtless affected by this chemical action, and undergoes also a partial process of inversion, and this most probably accounts for the disappearance of the light shade of ginger or fading of the darker-colored beverages. This is the result of our investigations.