It is known that the Egyptians coloured candy, and wine was coloured as long ago as 400 BC. Not only that, the developing food industry had to its disposal a vast array of synthetic colours in the late 1800s. This led to colours being added for decorative purposes and unfortunately to disguise low quality foods. There was no control over this use of colour and so inevitably legislation came into force. In particular, this was a result of health concerns raised over some of the toxic compounds used.
Eventually, an established list of permitted synthetic colours came into force in most countries early in this century. In the last 20 years, however, consumers have become increasingly aware of the ingredients in their foods and as such they require foods to be as `natural' as possible. This combined with technological developments has fuelled the increase in the usage of naturally derived colours. Today the food industry has an extensive colour palette available, allowing selection of the most suitable colour for their application requirements. Legislation is also in place to protect the consumer. Colour suppliers are however constantly striving to improve the technical and physical properties of their colour portfolio, to make the use of colour easier, to improve the stability and to meet customer demands on the functional additives used within colour formulations. This paper will review all colours in terms of recent developments and regulations as well as addressing the question of the future of colours in the next millennium.
Market trends
There are no reliable published statistics on the size of the colour market, however, on a global scale a reasonable estimate would be $940m which can be segmented.
In terms of individual sector size, it is estimated that the split is: d synthetic colours $400m; d natural colours $250m (of which $100m is in the USA); d nature identical colours $189M; and d caramel colours $100M.
Future growth is thought to be going to be greatest for naturally derived colours with a predicted annual growth rate of 5-10%. Synthetic colours are still forecast to grow but at a lower rate of between 3 and 5%.
Natural colours
Significant developments have occurred with natural colours since their wider commercialisation around 25 years ago - the growth in use of natural colours and chemical properties. Many are sensitive to oxidation, pH change and light and their inherent solubility varies widely.
There are currently 13 permitted naturally derived colours within the EU and 26 colours exempt from certification in USA. Table 3 details the colour shade and key characteristics of the most commonly used, permitted naturally derived colours.
Other colours exempt from certification within USA are; Ultramarine blue (limited to animal feed), toasted partially defatted cooked cottonseed flour, ferrous Gluconate, dried algae meal (limited to chicken feed), carrot oil and corn endosperm oil (limited to chicken feed). These have limited use either because of an application restriction or poor stability.
Natural colours were initially considered much `natural' products in light of their distrust for the food industry, based on unsubstantiated health scares related to additives in general, but especially related to hyperactivity and its perceived association with many azo dyes such as tartrazine.
Colour is spread widely throughout nature in fruit, vegetables, seeds and roots. In our daily diets we consume large quantities of many pigments, especially anthocyanins, carotenoids (nature is thought to produce in excess of 100 million tonne per annum of carotenoids, of which more than 600 structures have been identified) and chlorophylls. Our intake from naturally coloured processed food is fairly insignificant when compared to this.
Pigments from nature vary widely in their physical form, are less stable, more difficult to use and more expensive than the synthetic colours they aim to replace. It was always thought the colour shades achievable would be less vibrant and appealing.
It is estimated that worldwide up to 70% of all plants have not been investigated fully and that only 0.5% have been exhaustively studied. From this it could be concluded that we have only just begun our search for natural food colour sources. Unfortunately, however, most pigments fall into the classes mentioned above, making minor pigment classes rare. Any totally new pigment source would require safety assessment, which would be costly and time-consuming, prior to any FDA petitioning and EU approval for use as food.
Formulation
Developments in colour formulation over the last five years have focussed on augmenting the stability of the natural colourings.
Various emulsifying systems are used depending on the final application. These colours are characterised by excellent dispersibility and improved oxidative stability giving a stable, bright and easy to use yellow through to orange/red shades, for a range of food and drink applications.
Applications such as jellies, confectionery and certain beverages require bright stable colours with excellent clarity. Pigments that are normally oil-soluble such as carotenes and paprika can produce slightly hazy colours once emulsified.
This is overcome by the formation of microemulsion. Examples are the Varna Clear-Col emulsions from ITC Colors which offer crystal clear carotenes and paprika with excellent oxidative and acid stability.
Most recently developments with nature identical colours have focussed on removal of the functional peanut oil and bovine gelatine ingredients, allowing larger customer acceptance by removal of possible allergenicity concerns. Corn oil has been used to replace peanut oil and fish gelatine has replaced that of porcine origin.
d Less colour migration in applications such as desserts, when a fruit preparation is layered with pH neutral
Advances in spray drying combined with ingredient/ formulation technology has lead to the development of some microencapsulated natural pigments. High DE (Dextrose Equivalent) maltodextrins have been used to improve the stability of carotenoid pigments.
A new 7% CWS (cold water-soluble) beadlet formulation has recently been developed by Hoffman.
With synthetic pigments, process developments have focussed on producing `low dust' granularly Roche 998). This provides intense dyes. Traditionally dyes were manufactured in yellow shade (the 10% beadlet formulation is more orange) and an almost translucent dispersion. The formulation consists of fine b-carotene crystals in a matrix including corn oil, fish gelatine, maltodextrin, sucrose and silicon dioxide with the antioxidant benefits of Ascorbyl palmitate and dl-!-tocopherol. Application areas include soft drinks, confectionery and dairy products.
Process
Processing technology has had a significant beneficial effect on both natural and synthetic colours.
Milling of pigments to encapsulate them into an insoluble carrier has produced a range of suspensions with improvements over their solubilised counterparts. This technology has led to benefits for natural pigments such as: d Improved light stability (for example with curcumin), extending its areas of application to products such as sauces, dressings and soft drinks (Hansen, 1999); d Oil dispersible forms of naturally water dispersible pigments for example beetroot extract and amel; d A reduced level of certain additives, for example the emulsifier polysorbate 80, which has some legislative restrictions (i. E., for the Japanese market) and can cause problems in some food applications such as foaming and interactions with extruded applications such as breakfast cereals (Boyd, 1998).
The soft beverage industry accounts for a significant volume of food colours sold. This is based on the fact that colorful drinks are more appealing and they enhance the consumer's perception of flavour, fruit content and overall quality. All categories of colour are used; synthetic, nature identical, natural and caramel colours (for cola). Colour problems within the industry are mainly cited as:
d Colour fading/browning with the addition of ascorbic acid (vitamin C). This effect happens with red synthetic colours such as Ponceau 4R and anthocyanin based natural pigments.
d An unsightly orange/brown oily ring at the neck of principally orange `dilute to taste' drinks. This is attributed to the pigment (mainly b-carotene) suspension/emulsion breakdown and the gradual sedimentation.
d Using ascorbic acid as an antioxidant to prevent colour fading with carotenoids.
d Developing special colour emulsion/suspension formulations using acid-stable emulsifiers and synergistic antioxidant systems.
d Developing more acid-stable copper chlorophyllin colours by further solublising the pigment.
d Increasing the acid stability of carmine using microencapsulation technology.
d Future developments in US legislation
A petition has been made to the FDA to approve D & C Yellow 10 (similar to Quinoline yellow) and D & C Red 28 (Phloxine B, Purified) as food colours as well as Paprika Oleoresin. Both are currently used in drugs and cosmetics. It is anticipated however that the approval will take some time in the future. Colour suppliers will continue to mirror the flavour industry by offering bespoke formulations and pre-blends along with a comprehensive technical advice and sample service.
Novel pigment sources
Many novel pigment sources have been identified as potential new sources of natural colours (Francis, 1987). Some are currently used in certain countries but unfortunately approval as an EU/US food colourant would involve lengthy and expensive safety testing, which prohibits their commercialisation.
Monascus is a heat-stable red and yellow colourant derived from the fermentation of rice from the fungus Monascus purpureus and Monascus anka. It is one of the most commonly used natural colours in Japan and the Orient for applications such as meat and fish. It is not permitted within the EU or USA owing to concerns over potentially toxic coumarin compounds produced during the fermentation process.
Spirulina sp. contains the pigment Phycocyanin. This gives a blue shade and has the highest stability at pH 5]7. It is not permitted as a colourant source within the EU or USA. The FDA has classified Spirulina sp. as a cyan bacteria and considers it a food, not a vegetable, and as such it does not conform to the regulation 21CFR 73.260 on `Vegetable Juice however now approved.' It is, however, used in Japan. The application areas are limited to non-acidic foodstuffs such as chewing gum and dairy products.
Other sources of pigments include blue gardenia, the traditional orange carrot and purple corn which are limited by stability, price and legislation.
Functional food ingredients
There is growing evidence that many food components perform additional beneficial functions in the body. Our instinctive preference for eating naturally occurring coloured (for example fruits and vegetables) over bland foods is thought to be nature's way of providing our diet with certain phytochemicals.
Conclusions
Although many advances in the developments of food colours have been made over the last 25 years, particularly in terms of harmonised legislation and advances in processing and formulation technology, there is still room for future developments.The overall colour market is forecast to grow in line with technological and sociological changes that will lead to an overall increase in processed food stuffs. It is thought that the natural colour market will grow on.
