Adding natural tints to beverages can be a challenge for product formulators. Andreas Klingenberg and Penny Martin assess the current ingredients available and discuss acid, heat and light stability issues.
The use of natural colours in beverages continues to increase, due to the perceived need for overall naturalness of a product and demand for the full spectrum of natural colours with specific shades.
Natural colours can be used to provide appealing shades in a variety of beverage applications. However, it is important to consider specific issues regarding their use. These include regulations and technical properties of the colours, including stability toward heat, light, pH, ascorbic acid and interactions with other ingredients.
It is also necessary to consider the market needs of the region served. In the US, for example, a colour cannot be labelled as a ?natural colour? (except with a couple of nonpractical exceptions). Internal company policies then prevail. (See sidebar below.)
Beverage applications demand superior stability characteristics. With respect to recipe, shelf life and packaging, factors such as light, oxidation and acid stability, as well as the stability of the colour formulation, must be considered. This is particularly true if an emulsion is used.
Following is a review of the most commonly available and technically suitable natural colour systems available:
Beta-carotene: One of the most popular food colours, beta-carotene can be derived from carrots or palm oil by means of extraction or chemical synthesis. For economic reasons, the majority of beta-carotene used is nature identical. The oil-soluble beta-carotene compound is converted into a water-soluble formulation by emulsification. High-grade emulsions are characterized by the extremely fine dispersion of O/W emulsions, their acid stability and their resistance to oxidation and ringing. The addition of ascorbic acid helps to improve colour stability further. Used in low dosages, these beta-carotene emulsions impart a transparent bright yellow colour suitable for near-water beverages.
Lutein: Although not permitted as a colour additive in the US, xanthophyll lutein is permitted within the European Union as food colourant E-161b. In beverage applications, lutein achieves a very attractive, bright yellow colour hue. In addition, it possesses functional properties because recent epidemiological studies show a clear association between the intake of xanthophylls and a decreased risk of age-related macular degeneration. This suggests the protective effect of xanthophylls against AMD.
Paprika: This extract is an ideal choice to achieve a deep orange colour. By selecting sweet pepper fruits with low capsaicin content for extraction only, the formulation is very low in pungency. Advanced emulsification technology is used to achieve a formulation showing a high acid stability and superior oxidation resistance.
Canthaxanthin: A nature-identical, synthetically produced carotenoid exhibits orange-red shades in beverage systems. In general it is stable in ascorbic acid-fortified beverages. Cloud is imparted with canthaxanthin, and it is necessary to keep within the usage rate restrictions imposed.
Turmeric oleoresin: Although not commonly used due to poor light stability, turmeric is a vibrant yellow colour used in dry mix beverages and light-protected packaged beverages such as cartons and cans.
Anthocyanins: Found in many sources in nature including strawberries, raspberries, grapes, cherries, red onions, elderberries and cranberries, anthocyanins represent the largest group of water-soluble fruit and vegetable colourings. Commercial preparations are generally from fruits (elderberry, grapes and grape skins, and the hibiscus flower) and vegetables (black carrot, purple sweet potato, red cabbage and red radishes). They exhibit varying stability of yellow-red to magenta-red shades depending generally on source, expression techniques and food systems.
The commercially available vegetable juices—black carrot, red cabbage and purple sweet potato—contain acylated anthocyanins that yield the best stability of the anthocyanins available (di-acylated forms are the most stable). Due to the chemical makeup of anthocyanins found in grapes, elderberry and hibiscus, they are most suitable for shorter shelf-life systems, especially when ascorbic acid-fortified, as they may brown and fade over time.
Anthocyanins will change shade with a change in pH. They are most stable in systems with a pH less than 3.8 and are susceptible to degradation by ascorbic acid. With 250PPM of ascorbic acid, up to 50 per cent anthocyanin colour loss can be expected within a short time (one to three months) in a fortified beverage coloured with red cabbage, purple sweet potato or black carrot.
In most beverage systems coloured with the above-mentioned vegetable juices, colour fading is the issue—not browning. However, with certain other anthocyanins, both colour loss (much quicker than the vegetable juices) and colour changes (browning) can occur depending on source and expression/extraction techniques employed.
Cochineal extract and carmine: These stable orange to bright magenta colours are well known. Cochineal extract is the result of carefully controlled extraction from a female insect called cochineal.
Cochineal/carmine-based colours are commonly used due to the appealing range of shades available, their excellent stability (especially in the presence of ascorbic acid) and their cost-in-use ratio vs. other products. Unfortunately they are not readily accepted as kosher, a limiting factor in many markets. Cochineal extract and carmine have good to excellent heat- and light-stability qualities in beverages, depending on ingredients. In low pH, hot-fill beverage systems, orange cochineal extract will not lose any strength during hot fill nor during the shelf life of the product.
Conversely, over time, acid-stable cochineal extract will lose some of its ?blue? notes, becoming more of an orange-red shade. Ascorbic acid in the range of 200-400PPM will enhance the stability of cochineal extract products in beverage applications.
Carmine is also one of the few products that will survive retort conditions for those canned nutritional beverage products where certain synthetic colourants are found to be limiting. Retort conditions are typical for canning, where heat processing is done under pressure.
Beet juice: Although not used in ready-to-drink beverage systems due to poor stability, beet juice is commonly used in the US in dry mix beverage formulations. Beet juice is classified as a vegetable juice colour additive in the US. It is a magenta-red liquid or spray-dried powder.
Bioactive colour concepts
In addition to their colouring, many natural colours can provide further health benefits, especially carrot, elderberry and grape extracts and concentrates. These products contain all the valuable secondary plant components from the fresh fruit or vegetable and they offer superior functional benefits compared to isolated substances.
Penny Martin is manager of technical services, Sensient Food Colors, North America.
Andreas Klingenberg is director of technical services, Sensient Food Colors, Germany.
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