Developments in natural colourings

Nielsen, S.R. and Holst, S., Developments in natural colourings, in Color in Food Improving Quality, MacDougall, D., Ed., Woodhead Publishing, Cambridge, U.K., 2002. 

Vitamins occur naturally in many foods and raw materials. However the natural contents are often supplemented in many food products to ensure an adequate intake, for example in infant formulae, breakfast cereals and clinical nutrition products. Vitamins are usually added as nutrients and thus not covered in this chapter but may also be added as food colours (riboflavin, carotenes). The reader should refer to the following references for recent developments in... 

Kondo, T. et al.. Structural basis of blue-colour development in flower petals from Commelina communis. Nature, 358, 515, 1992. 

In more recent times, through parallel developments in chemical science and engineering, natural materials that once formed the basis for colouring, dyeing, and flavouring, for foodstuffs, perfumery, pharmaceuticals, and textiles, gradually have been superseded by substances similar or even the same from the point of view of chemical nature, but which have little direct connection with the flora and fauna of the planet. (The substitutes are facsimiles, not extracts.)... 

Earthcycle has developed a line of packaging specific for fresh vegetable and fruit. The packaging trays are water resistant and are available in two colours, natural fibre and vanilla. Other colours are available upon request, using vegetable dyes, so the biodegradability and compostability of the product is not jeopardised. 

Drugs that contain two phenolic groups, such as adrenaline (epinephrine) and other catecholamines such as noradrenaline (norepinephrine) and isoprenaline are particularly susceptible to oxidation and have to be formulated at acidic pH. All of these compounds are white crystalline solids that darken on exposure to air. Adrenaline forms the red coloured compound adrenochrome on oxidation (Figure 8.10), which can further polymerise to give black compounds similar in structure to melanin, the natural skin pigment. Injections of adrenaline that develop a pink colour, or that contain crystals of black compound, should not be used for this reason. Adrenaline for injection is formulated as the acid tartrate... 

The improvement of photostability of jute fabric itself is an important matter to be given priority. Various processes have been developed in which bleached jute does not revert to its natural colour on exposure to light. The blocking of reactive phenolic groups by etherification or esterification is expected to arrest the yellowing process. The presence of some chromophore in dyes can cause absorption of near uv-radiation of sunlight and prevent discolouration. Bleached jute goods treated with copper-potassium dichromate (0.25% o.w.f) improve photostability over conventional bleached fabric [123]. 

Many food and beverage manufacturers are still reluctant to nse natural colours due to former issues such as dull colour shades, poor stability with rapid fading and difficulties in handling. However, over the past ten years natural colour manufacturers have discovered new techniqnes within formulation and processing that are able to resolve these issues. Combined with the use of high-quality raw materials it is now possible to develop and manufacture products that have better functional properties both daring handhng and in the final food products. 

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