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Coloring Food, Naturally

The effort to eliminate synthetics gives chemists the blues

by Melody Voith
December 15, 2008 | A version of this story appeared in Volume 86, Issue 50

New hue
Credit: K. Santos
Natural color makers have recently turned to purple sweet potato as a stable source of purple and red.
Credit: K. Santos
Natural color makers have recently turned to purple sweet potato as a stable source of purple and red.

FOOD MAKERS wishing to impart a bright hue to their products can choose from among a full range of synthetic colorings. But changing consumer preferences and the specter of new regulations have sent food industry insiders in search of natural alternatives.

It's not exactly a rainbow of possibilities, they are finding. Cheese makers are fortunate that plant-based yellow and orange food colors have been available for centuries. They still use annatto—derived from the seed of a tropical tree—to give cheddar its distinctive look. Now, the rest of the food industry is looking to ingredient makers to complete the color wheel with stable, naturally derived red, purple, green, and blue.

"There's not a day that goes by that I don't get a call—or five—asking how to substitute FD&C red No. 40," says Theodore Palumbo Jr., technical director and color chemist at International Food Craft, an ingredients supplier. Red No. 40—known by only a few as 6-hydroxy-5-[(2-methoxy-5-methyl-4-sulfophenyl)azo]-2-naphthalenesulfonic acid—is the color responsible for the vibrant hue of maraschino cherries. "What's driving the market is public fear of chemical additives," he observes.

Concerns about additives are changing the food market, according to industry consultants at Leatherhead Food International. LFI estimates the size of the global market for food colorings at $1.2 billion per year. Natural colors are just 31% of that market, but they are growing at 5% a year, while synthetics are growing by only 1%.

With the increasing importance of natural colors, many of the larger synthetic color houses have diversified to include natural products. For example, flavor and fragrance maker Sensient Technologies expanded its natural colors business through acquisitions in the 1990s. Currently, 25% of the company's color business is in the natural category.

In Europe, efforts to replace synthetic colors have recently become urgent. A U.K. study linked mixtures of artificial colors and the preservative sodium benzoate to hyperactivity in children (Lancet 2007, 370, 1560). On the basis of the findings, the U.K. Food Standards Agency has asked food makers to remove six artificial colors by the end of 2009. In the European Union, regulators have proposed to require foods containing the colors to include a label stating, "Consumption may have an adverse effect on activity and attention in children." The requirement will likely come into force in 2010.

This means that food makers must make the most of the common natural colorings available today. In addition to annatto, sources for these colorants include carrots, beet powder, caramel, cochineal extract, fruit and vegetable juices, grape skin extract, paprika, saffron, and turmeric.

In the U.S., the Food & Drug Administration must approve all food additives, even those derived from edible plants. FDA does not allow food makers to label any ingredient a "natural" color, which means that consumers have to draw their own conclusions when they see "beet powder (for color)" in the ingredients list. Only food that is colored with its main ingredient—for example, strawberry ice cream colored with strawberries—may say on the label that it contains no artificial coloring.

TO GET RED and blue, food makers usually rely on anthocyanins from fruit and vegetable extracts, but those compounds tend to be unstable. Obtaining an appetizing natural green is a particular headache in the U.S. because FDA doesn't allow the use of plant-derived chlorophyll as a colorant. Many food companies resort to spinach juice.

Ingredients makers who work with food companies to find substitutes for synthetic colors say it is often difficult to preserve the original look of a product, says Claire Cormack, marketing manager at U.K.-based Overseal Natural Ingredients.

Overseal urges marketers to consider color requirements early in new product development, because some foods cannot be naturally colored to the maker's desired specifications. Green isn't as big a problem in Europe because chlorophyll is permitted there. For Cormack, the tough natural color is blue.

"While some colors can be matched, others are almost impossible," agrees Gabriel J. Lauro, director of research for natural color firm ColorMaker. "Some synthetics have a fluorescence, whereas most naturals are not as bright, so they look a little dull in comparison."

According to Lauro, the biggest marketing problem is that color has become a signal of quality for many consumers. "We struggle here to match colors as close as we can to artificial, holding artificial as the gold standard," he says. In most cases, the desired hue can be achieved only through the use of a color blend developed specifically to work with a particular food or beverage.

The list of food characteristics that can make or break a good natural color is long, according to Lauro and Cormack. Some foods require liquid additives, whereas others call for solids. Water versus oil solubility is also an issue. And food scientists need to consider whether their product will be heat processed or whether the packaging will expose the product to light.

Presto Chango
Credit: K. Santos
Cyanidin is a glucose-bound anthocyanin responsible for the color of purple potato, red cabbage, and dark berries. When added to food or beverages, it imparts a color that varies dramatically from red to a dull blue depending on the product's pH.
Credit: K. Santos
Cyanidin is a glucose-bound anthocyanin responsible for the color of purple potato, red cabbage, and dark berries. When added to food or beverages, it imparts a color that varies dramatically from red to a dull blue depending on the product's pH.

When it comes to choosing and blending plant anthocyanins to add coloring to food, the most striking variable is the pH of the food. Cyanidin, an important anthocyanin found in dark fruits and vegetables, acts like a pH indicator. In an acidic beverage such as soda, it imparts a bright red color, but as the environment becomes more basic, the molecule loses hydrogen ions and turns purple, then dull blue.

In addition, anthocyanins vary in type, concentration, and characteristics depending on the plant source. Although grape skin used to be a preferred source, red cabbage, purple carrot, radish, and most recently purple sweet potato are used today for the improved stability of their anthocyanins in food. They contain anthocyanins that are acylated, which improves their degradation resistance to heat, light, and long-term storage, according to Lauro.

BUT GETTING BLUE in foods with neutral or low pH calls for more tweaking. "We're still working on it. If you modify it too much, it's not natural anymore," Lauro says. ColorMaker's new, more stable blue colorant solution is made with red cabbage liquid but also includes aluminum sulfate and sodium bicarbonate as pH buffers.

The addition of aluminum sulfate may stretch the definition of "natural" in the context of food. But according to International Foodcraft's Palumbo, there is no consensus on the definition of "natural." His customers do rely on a few guidelines, such as the Department of Agriculture's organic standard, which has specific inclusions and exclusions for colorings. Another common request is to make the coloring "Whole Foods-friendly."

Whole Foods, a natural and organic grocery chain with locations across the U.S. and U.K., acknowledges its role as default regulator of natural food ingredients. "That's the niche our company fills," agrees Joe Dixon, the firm's quality standards coordinator. "We were founded because of a growing disappointment in natural product availability."

The company maintains a list of unacceptable ingredients for food that includes synthetic colors and aluminum sulfate. "We will look at an individual color if a vendor comes to us with something new. We ask, 'Where does it come from, how is it made, is it safe and legal, and is it something our customers would expect to find in a natural food store?'" Dixon says.

Palumbo points out that the "Where does it come from?" question embodies many modern-day concerns about food sourcing. His customers are now wary of ingredients from China, and they want proof that they come from crops that have not been genetically modified. Also anxiety-producing for food makers and sellers turning to naturally derived colorants, Cormack adds, is that "there are certain issues that can affect supply—for instance, climate change, bad crops, the economy, and political unrest."

The most difficult challenge remains getting the right color, and for that food makers are counting in part on changing consumer expectations. "Slowly, consumers are weaning themselves away from synthetics," says Lauro, who anticipates a trend toward visually natural colors. This could mean the end of kid-attracting blue ketchup and tongue-painting candy.


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