Factors in selecting natural colours

Some ingredients such as sugar and protein have a tendency to stabilise most natural colours, whereas others, i.e., salts, some colloids, ethanol and sometimes flavours, may have a negative influence on the stability of the added colonr. High amonnts of ascorbic acid, sulphur dioxide and other antioxidants may 

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Acid stability of the colour is required in low pH applications like soft drinks and many confectionery products. Alkaline formulations of chlorophyll and annatto colours are the most sensitive, and acid-proof formulations should be preferred. However, increased acid stability may be achieved if the annatto pigment noibixin is able to bind to protein, e.g., fruit pulp in fruit based beverages. 

Alkaline carmine formulations can be used in acid conditions if the colour is entrapped in the viscous food matrix. Hence water-soluble carmine has excellent stability in ice-lollies, hard-boiled candy, gums, jellies and the like. If used in a non-viscous product, e.g., soft drinks, the aluminium bond in the carmine may break and the colour will precipitate thereby changing hue towards a more orange shade. 

Some colours, like all the different anthocyanins, change colour shade with varying pH. At pH around 3, where they are most commonly used, they will display bright pink and reddish hues. Moving towards neutral pH the colour will change through purplish-red to mauve and bluish shades and, depending on the anthocyanin source, can even appear dull and dark. 

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