March 1, 1994
Every food designer knows that consumers judge a product not only on its flavor, but on its appearance as well. One important class of ingredients exists solely to enhance the appearance of what we eat: food colors. In recent years, product designers have been asked to formulate using so-called natural colors with increasing frequency. This presents a set of challenges that is totally different to those presented when using certified colors. As any artist would say, it's primarily a matter of understanding the palette and correctly applying the colors.
Federal regulations govern the use of all coloring agents and separate them into two general categories: certified and exempt from certification. These are commonly referred to as "artificial" and "natural" throughout the industry. Title 21, Code of Federal Regulations (CFR), Parts 70 through 82, regulates the use of all food colors.
Certified Colors. The U.S. Food and Drug Administration has approved seven synthetic dyes for use in food products. blue #1, blue #2, green #3, red #3, red #40, yellow #5 and yellow #6. Generally, the names are preceded by the modifier FD&C (i.e. FD&C Red #3).
In addition to the FD&C dyes, the other class of certified colors is known as FD&C lakes. These consist of the aluminum salts of FD&C dyes extended on an insoluble substrate of alumina hydrate. Calcium salts are permitted but are not commercially available. Lakes of all of the FD&C dyes except red #3 are permanently or provisionally listed. FD&C red #3 Lake was delisted in 1990.
Non-certified or Exempt Colors. The class of coloring agents typically referred to as natural is defined by the FDA as "exempt from certification" and listed in 21 CFR Part 73. These consist of twenty-six colorants made up of dyes, pigments or other substances capable of coloring a food that are obtained from various plant, animal or mineral sources, or are synthetic duplicates of the same.
"Not all of the exempt colorants are derived from natural sources," notes Carol Riddle, senior chemist, customer technical services, Hilton-Davis Co., Cincinnati. "Some, including beta carotene, are synthetically made. That's why I prefer the term 'exempt' to 'natural.' "
"It's important to note that all of the exempt colors must meet FDA specifications," observes Sue Ann Babcock, senior chemist, natural colors, for Warner Jenkinson's Color Div. in St. Louis. "It's a positive list -- just because you extract something from a natural source doesn't mean you can add it to foods. It has to meet a certain specification that can be very broad or very specific depending on the color. For example, carmine must contain not less than 50% carminic acid. Cochineal extract must contain not less than 1.8% carminic acid, with a pH falling between 5 and 5.5."
Many of these colors are restricted to use either in particular products or at specific levels and therefore may not be widely used for coloring foods. The exempt colors include:
Caramel color is one of the most widely used colorants used in foods and is made by heating food grade carbohydrates, generally a high dextrose-containing starch hydrolysate or corn syrup.
Caramel color is soluble in water and produces a color ranging from golden brown to nearly black. The color strength is defined as its tinctorial power -- the absorbance at 560 nanometers measured spectrophotometrically. The color tone, defined by the hue index, measures the red characteristics of the color. Generally, the higher the tinctorial power, or strength, the lower the hue index, or red tones. Some caramel colors are termed "double strength." This is a relative term and varies with the color range. The specific gravity indicates the solids content and therefore the strength of the color.
The majority of caramel color carries either a positive or negative ionic charge. Negatively charged product uses sulfite in its manufacture and although it is molecularly bound, can be detected chemically. Because the FDA mandates sulfite labeling in products containing over 10 ppm, the level present in a specific type of caramel color may become a formulation consideration.
"The ionic charge of the caramel color determines what caramel color should be used in what product," reveals Dean A. Bodnar, vice president and technical director of Sethness Products Co., Clinton, IA. "The color interacts with other food components carrying the opposite ionic charge. About three quarters of the domestic caramel color carries a negative charge. There is a small amount manufactured with a slight negative charge chemically that is referred to as neutral."
Turmeric is a bright yellow colorant made from the roots of the herb Curcuma longa L. The pigments responsible for the color are known as curcuminoids: curcumin and related compounds. Turmeric's solubility depends on the medium in which the pigments are dispersed and the process. For instance, turmeric oleoresin is water-soluble; but a suspension of turmeric extract in oil can be added to fat-based systems. At high pH this colorant turns orange. There is no usage restrictions as long as the level conforms to Good Manufacturing Practices (GMP).
Annatto is another yellow food colorant. It comes from the seeds of the Bixa orella tree. The pigments that produce the yellow to orange color range are the carotenoids bixin and norbixin; the concentration is expressed as a percentage of one or both of these compounds and the content varies with the extraction method. The pH, emulsifiers and the overall solubility affect the hue; the greater the solubility in oil, the brighter the color. Water- and oil-soluble, and oil/water dispersible forms of annatto are available. Because it may precipitate or turn pink at a pH less than 5, suppliers have developed specially emulsified acid proof versions.
Beta-carotene is a precursor for vitamin A in addition to imparting an orange-yellow color to food. Most beta-carotene is derived from algae or synthesized. Beta carotene is oil-soluble but can be made into a water-dispersible emulsion. No restrictions have been placed on the level of use and it is listed as GRAS (Generally Regarded as Safe).
Paprika oleoresin is extracted from the pod of Capsicum annum, or paprika. It contains three main naturally occurring pigments: capsanthin, capsorubin and beta-carotene. This combination produces a bright orange to red orange in food products. The oleoresin is oil-soluble, but when emulsified becomes water dispersible.
Red cabbage juice produces a bright pink to red color in products with a pH of less than 4. A higher pH causes the anthocyan-based pigments to turn an unstable purplish blue color. The product dissolves in water, but not in oil.
Beet juice in either liquid or dehydrated form contributes a bluish-red color produced by a compound known as betanin which is stable at a higher pH range than red cabbage juice. There are no limits on its usage level. When used at high levels, though, it contributes a characteristic beet flavor.
Grape skin extract imparts a reddish purple color to beverages. However, the FDA restricts its use to alcoholic beverages, beverage bases, still and carbonated drinks, and "ades".
Carminic acid, which is derived from the shells of certain species of insect, produces a magenta red shade and is the pigment present in carmine colors and cochineal extract. Water insoluble lake forms of carmine exhibit a color range from pink to purple. Unlike the colors derived from plant sources, these are not Kosher certified. Carmine will not be stable at low pH unless an acid-proof version is used. It is, however, very heat stable.
Titanium dioxide not only colors food products white, it imparts an opaque appearance. Both water- and oil-dispersible versions are manufactured. The FDA limits its usage in food products to 1% by weight.
Other non-certified colors: Other additives can be used in food products as colorants, but their use is limited because of cost (saffron), limited application (Ferrous gluconate – only in black olives), or non-human consumption (Tagetes meal from marigolds is for chicken feed only).
As previously mentioned, federal regulations govern the use of all colors in this country – certification for so-called artificial colors, both dyes and lakes; application and level restrictions for the so-called natural colors. There's a reason for the use of "so-called" here. Although most people in the industry would know to what these terms refer, the FDA does not.
"It's important to define the term natural color because it makes a difference in the perception of what is permitted from a formulation standpoint," explains Babcock. "Sometimes marketing wants a particular label look -- something that can be called natural. FDA regulations (21 CFR, section 70.3) do not consider any color that is added to a food product as natural, no matter what the source of the color. The only exception being if the color is 'natural' to the food product itself, such as coloring strawberry ice cream with strawberry juice.
"The FDA says that if you use beet juice to color strawberries, that beet juice is a color additive, not a natural color," Babcock continues. "As such, it must be labeled as color added, artificial color or by name with purpose, according to 21 CFR, Section 101.22. The term 'natural color' is not a permitted label statement."
As specified by the Nutrition Labeling Education Act (NLEA), effective in 1993, certified colors – both dyes and lakes – must be listed in the ingredient statement by name. This is a change from the previous regulations that only required the term "artificial color" unless yellow #5 was added, which then had to be specified by name. The FD&C prefix or the designations "No." or # are not needed, just the name and number. The term lake must be included if the color is a lake.
Natural colors – or more accurately, those exempt from certification -- must appear on the label as "artificial color," "artificial color added," "color added", or "colored with...(the name of the color as it appears in the regulations)."
For brevity, most suppliers and processors (and this article) will most likely continue to use the terms natural and artificial when referring to the two classes of colorants. Care must be taken, however, so this doesn't carry over to the label.
With the knowledge of what's on the palette and what the government wants it called, it's time to begin work on that culinary masterpiece. It starts by narrowing down the dazzling array of possibilities to find the color or combination of colors that best meets the product requirements. As with any decision-making process, it's best to assign a relative importance to each issue in case a compromise is necessary. It's important to remember that a single coloring agent may not give the desired effect and that blends, including both natural and artificial, may be necessary.
Several properties must be considered here – the actual color, its intensity and the degree of clarity or opacity required. Some of this depends on the product itself. Adding color to chocolate won't turn it pink. On the other hand, you can make a light colored icing appear to be rich, dark chocolate.
"Background colors and additional ingredients will make a large difference in how a color will look," says Riddle.
Adding titanium dioxide provides opacity by blocking transmitted light, but because it has a lightening affect, pastel colors generally result. This opacifying property also can help low fat products such as cheese or salad dressings mimic the opacity contributed by fat.
"Adding water-soluble colorants to a water-based system will not affect the clarity or opacity of the product," Riddle states. "Using oil-soluble exempt products is used to produce a cloud. They will stay in suspension as long as you have a properly balanced emulsion."
"In terms of the naturals, anything that is oil-soluble and you want to make water-soluble, in all likelihood, will create a cloud in a clear product like a beverage," Babcock notes. "An example is adding water dispersible beta-carotene to an aqueous system."
Product concepts requiring blue or green limit the choice to certified colors only. Chlorophyll, although widely seen in nature as a green colorant, is only permitted for use in dentrifices or cosmetics at very low levels. Bluish purple can be achieved with carmine, but it doesn't create a true blue.
Annatto or turmeric tend to represent a cheese color or have an "eggy" tone compared with the bright color produced by the FD&C yellows.
"These days everyone wants fluorescent food colors. They want them to glow under UV light," explains Riddle. "None of the certified colors will do this. Turmeric is highly fluorescent and so are some additives like the Tweens."
As mentioned, as far as the label is concerned, natural colors do not exist. But there are certain phrases that, because of public opinion, may be construed as more benign, such as "colored with paprika extract", or even as an advantage, such as "colored with beta-carotene." Kosher approval for the product rules out carmine and cochineal extract.
"There's a lot of information coming out regarding the health benefits of beta-carotene," points out Carol Locey, color product manager for Kalsec, Inc., Kalamazoo, MI. "Although no health benefits can be claimed on labels, there is an advantage in listing carotene based on consumer recognition. While consumer knowledge about beta-carotene is high, there isn't nearly as much awareness of the antioxidant properties which the carotenoids in paprika and annatto provide."
A number of physical and chemical characteristics of the food product itself affect the choice of a colorant. Some additives, such as caramel color and carmine, are fairly stable to changes induced by these.
The pH particularly influences the hue, the intensity and the stability of natural coloring agents. Acidic conditions cause annatto to turn pink. A pH over 7 causes turmeric to appear red and to fade rapidly. Acid affects the solubility of FD&C #3 and it should not be used if the product pH is under 5.
"To some extent, pH-induced color changes are reversible," explains Babcock. "It really depends on which color and how long and how severe the pH is."
The presence of oxidizing and reducing agents often causes color changes. Metal ions like iron, copper magnesium and aluminum can catalyze oxidative color loss in many food colors.
"Sport drinks can be difficult to color because of all the ions," observes David Frick, laboratory supervisor for Warner Jenkinson's color service laboratory in St. Louis.
Active bacteria such as those found in fermented products can break down certain colors. "In the active culture yogurts, lactobacter can cause color problems," cautions Riddle.
One of the keys to coloring a product successfully is the even distribution of the coloring agent throughout the finished product. Depending on the color, this can be achieved through solution, whether oil or water, or by dispersion. The addition of an oil- soluble color such as certain forms of annatto, would be appropriate in fat-based products like margarine, while a water soluble dye works best for a beverage.
Other colorants, including titanium dioxide, color foods by the dispersion of tiny insoluble particles of pigment. Because the particles tend to agglomerate, high shear is required to break them down and distribute them evenly. Failure to disperse them properly results in a mottled appearance due to speckling and reduced color intensity in the finished product.
"Another problem you may run into is that a product may not have enough viscosity to hold the color in suspension," cautions Babcock. "Or in the case of a product with pulp, the pulp may not hold onto the color as well as the liquid does."
High temperatures affect the stability of most colors – particularly FD&C red #40; the fruit and vegetable juices, like beet juice; and the carotenoids, especially annatto. The longer the period of heat application, the more severe the effect; according to Babcock, this doesn't mean that a HTST (High Temperature Short Time) process will give food product designers an advantage. To minimize the problem, the colorants should be added as late in the process as practically possible to ensure adequate dispersion throughout the mix.
"Most colors do not hold up well in typical retort situations," notes Frick. "The degree varies with the color, but the problem occurs even with FD&C dyes. Red #3 is relatively stable under retort conditions, while red #40 fades rapidly."
"Some products containing proteins (like pet foods and nutritional supplements) are especially problematic with high heat. There must be a reaction that attacks the azo-bonds on the certified colors. Along with red #40, some of the naturals will hold up – a cathazathan and a beta-carotene and carmine, but that's about it," says Riddle.
Caramel color is not sensitive to heat degradation, as it is the result of a high-heat manufacturing process. It takes extremely high temperatures to affect them.
"For most heat processes, such as baking, one wouldn't expect any changes," Bodnar explains. "But any change that occurs with retorting would be the result of chemical interactions between the meat proteins and the caramel-color bodies. The caramel color chromophores, which create the brown color, are large random non-repeating polymers – from 2000 up to 100,000 in terms of molecular weight. With the ionic charge they carry, they're analogous to the proteins."
Nearly all food products fade with time. Exposure to light, especially sunlight, hastens this process in foods containing coloring agents. This is a major consideration when clear packaging is used and the product is expected to be displayed on a shelf. Among the natural colors, turmeric exhibits extreme sensitivity to light. Annatto, beet and cabbage colors are also among the more light sensitive non-certified products.
"If you don't have an oxygen barrier in your packaging, you can sometimes get oxidative rancidity from the carotenoids," warns Babcock. "They're good oxygen scavengers, which means they will readily oxidize."
Cost and availability
Even though colorants are added at fairly low levels, cost is often an issue. In general, the artificial colors cost less than the natural colors; but not in all cases. Caramel color often costs less to use than a brown blend made from the FD&C colors. However, carmine is notoriously expensive, costing several hundred dollars per pound. It does have superior stability, especially for a natural color, so the resultant finished product may often justify the cost.
"Although the price of colors can be high, one has to remember that the actual cost or cost-in-use is what's important," advises Frick. "Colors are used in micro amounts, so while a color may be costly, changing to a less costly one may affect the product quality with little difference in the price of the finished product."
Natural colors may not always be readily available. They are derived from natural sources and their availability often hinges on climactic or political conditions.
Solutions in process
Several production considerations attach themselves to color use in food products. First of all, most colors in dry form create dusting. This causes a range of problems -- from cross-contamination of other products to workers breathing in the airborne particles. Agglomerated particles, plating colors onto appropriate carriers or pre-measured packets cut down on the problem but are more costly than standard products. More often, the answer is to put the product into solution. This minimizes dusting and also allows the colors to be added volumetrically. In addition, putting colors into solution helps to evenly distribute the color throughout the product.
There are several caveats to color solutions. The first of these is assuring consistency and accuracy of the solution preparation. Batch-to-batch variation in the color solution means batch-to-batch variation in the final product.
Second on the list is solubility. Aside from the obvious (water soluble in water and water-and-oil soluble in oil), designers must consider the different solubility rates. Not only do solubility rates of colors vary, the rates can vary depending on the medium.
When making stock color solutions, it is important to remember several things that affect the color stability: the presence of metal ions, both in the water and the storage and mixing vessels; the storage conditions, including exposure to light, heat, etc.; and the shelf life. If color is to be kept overnight it should be refrigerated, or preservatives such as sodium benzoate used.
"Some caramel colors are more salt-tolerant than others," says Bodnar. "We have caramel colors that are soluble in 20% sodium chloride and they're typically used in compounded soy sauce products. Some have a good phosphoric acid haze tolerance. This has to do with the preparation of cola concentrate where the color is in the presence of 75% phosphoric acid for months."
When adding natural colors to foods, a number of unexpected problems can occur unless the food product designer is on the lookout for them.
Fading is the number one problem encountered with food products. The first thing to look at is the color stability under the usage conditions. That means not only determining if the color is stable in the finished product, but also during the process. Adding color during a premix stage when the pH is out of the appropriate range or mixing it together with acid causes loss of color. Ascorbic acid used for vitamin fortification creates this problem. Fading also occurs when water with a high metal ion content is used. As mentioned, many of the naturals have severe problems in this area.
"One thing people often don't consider is the quality of their water," Babcock relates. "Many times the ions will affect the shade and stability of the colors, particularly the naturals. For example, calcium in hard water can cause annatto to precipitate. Often, the water source in the lab is deionized, where the water used in manufacturing may lack these treatments."
If a dry mix contains a blend of different water-soluble colors in powder form, they may solubilize at different rates. When the consumer expects orange in a powdered beverage, and then sees red and yellow water is added, he or she may think something is wrong with the mix. This is known as flashing and can be eliminated through the use of readily available monoblends.
Because colors fade at different rates, a blend may appear to change color with time. Another type of fade problem occurs if the packaging contains a clear window. If the package is exposed to light, the area under the window lightens considerably while the rest of the product retains its normal color.
Sometimes certain constituents of a product can interfere with the solubility of colors. A good example is when a flavor contains water-miscible solvents, such as alcohol or propylene glycol, that reduce the solubility of some colors.
Water-soluble colors often bleed into an uncolored or differently colored portion of the food. This is commonly seen in high-moisture systems -- for instance, a piece of fruit in a colored gelatin dessert will pick up the color upon storage. This is a situation that might require the use of a certified color such as the lakes. For this very reason, they are often preferred in cake icings. The same predicament may occur if a liquid fat containing a soluble color migrates to another portion, although this occurs infrequently.
"Color migration also can occur outside of the product," cautions Locey. "We've seen pasta where the water soluble color comes out during cooking. We've also had breading systems where a portion of the color moves into the frying oil."
"For sausage casings you're looking for a color with an affinity for protein," notes Riddle. "They need to stay in the casing and not migrate into the meat because it's not permitted to dye the meat."
In most cases, the product affects the color, not the other way around. But sometimes the color alters the product. Some natural colors, especially beet, can produce undesirable flavors if used at too high a level.
According to Bodnar, adding a negatively charged caramel color to beer causes a precipitate to form. "It co-precipitates with the soluble cereal proteins left in the beer and it results in a pile of sludge left on the bottom."
On the plus side, some natural colors can bind with proteins, thereby increasing the color stability.
"Several of the colors – including annatto – have a calcium sensitivity and form an insoluble calcium salt in the presence of calcium ions," observes Riddle. "Most of the flavor emulsions for beverages are made with gum arabic which contains a large amount of calcium."
A color may affect the package as well as the product itself.
"Occasionally you'll see a reaction in canned products," points out Riddle. "When you have anionic colors, they can cause depolarization. Over long-term storage that may damage the can lining. Plus, that's when you get color disappearance because of metal contamination."
Getting the hue down
Another important detail to remember when working with natural colors is that more is not necessarily better. There comes a point of diminishing returns, where adding more color makes a product duller instead of providing a bright, clear color.
"Optimizing the color level is basically a matter of trial and error," Locey remarks. "If a particular dosage is found to be acceptable, I would recommend experimenting with both higher and lower levels. If a 50% lower dosage rate results in the same color hue and intensity, a significant cost savings will be realized."
The experts suggest that coloring a product become an integral part of the development process. This way it is easier to head-off those unpleasant surprises.
"People have to remember that colors are chemical systems, too," Babcock reminds us. "You've got to keep the basic chemical principles in mind."
There's a lot more to adding natural colors than tossing them in at the end of the process. If food product designers pay close attention to how they work in your system, in the end they are likely to design a culinary masterpiece.
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