Natural food and beverage colourings - Natural Food Additives, Ingredients and Flavourings - page 26

to replicate this specifi c shade by blending curcumin and annatto. Annatto is an
orange pigment and, in combination with the lemon yellow of the curcumin, the
carotene shade is replicated. To colour yellow fats, a dispersion of curcumin in oil
is prepared and typically sunfl ower oil is used. Unlike water-soluble formulations
it is possible to blend the oil-soluble curcumin and annatto together to give a
single product to add to the oil phase of margarine prior to the formation of the
emulsion. The use of carotene as a margarine colour gives no fl exibility of shade
but, by altering the ratio of curcumin and annatto used in the blend applied to
margarines, it is possible to provide some variation for brand differentiation.
Water-soluble blends of curcumin and annatto are also available as pre-made
blends for ice cream where together they give the required vanilla shade.
Curcumin is extremely heat stable and may generally be used in products
throughout the acid pH range. As the pH increases, the green hue diminishes
above pH 7.5 and ultimately at above pH 8.5 curcumin becomes orange/red. In
some extreme cases where curcumin is exposed to very alkaline pH it can appear
pink. This is often seen in curcumin coloured bakery pre-mixes where alkaline
agents such as bicarbonate are poorly dispersed and pink spots become evident
over time.
The main limitation of curcumin as a food colour is its lack of light stability.
Water-soluble curcumin formulations applied to a clear beverage displayed in
direct sunlight would lose visible amounts of colour within a few days and fading
rapidly to complete colour loss. One solution is to use opaque packaging to protect
the curcumin-coloured material from the light. Light is the driver for the colour
loss but the mechanism involved requires free water in order for it to proceed. As
a consequence of this, applications such a hard boiled candy show no colour loss
because the free moisture of this product is so low. It is also possible to demonstrate
this in the laboratory by colouring alcohol and, after a period of no colour loss, it
is possible to instigate colour fading by the addition of water. Manufactures of
curcumin formulations have adopted formulation-based strategies to try and
overcome this; these use dispersion and encapsulation technology. It is possible to
make a water-dispersible form of curcumin by milling high strength curcumin
powder into low water containing bases such as sugar syrup. The shade is more
orange and less vibrant than the truly water-soluble version but it does have
enhanced light stability. An alternative approach is to use encapsulation
technology 2 where a coating is used to protect the curcumin whilst still allowing
its vibrancy to be seen.

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2.2.2 Beetroot
Red beetroot has been grown and used as a traditional salad vegetable for many
thousands of years. This root vegetable grows in temperate climates and its juice
is extracted and standardised for use as a food colour. The colour shade can vary
depending on the variety, environmental factors impacting on the crop and the age
of the extract. The age of the extract is an interesting point as over time the blue
notes of beetroot juice can diminish giving a more strawberry hue. The skill of the