Natural ingredients are the gold standard in the food and beverage industry today, and food colorants are no exception. The wave of consumer demand for both cleaner labels and the perception of healthier foods is leading—perhaps, at times, forcing—changes in the types of ingredients used in processed foods.
As these challenges yield to technical solutions, there’s a steady increase in the use of natural colorants in applications that traditionally relied on synthetics.
Definitions (or lack thereof) for “natural” and “clean label” are generating substantial concern, and even anxiety, in the food industry. A perfect illustration is the recent spate of lawsuits contending that products claiming to be “all natural” are misleading consumers. The claim is that ingredient content that does not meet the aggrieved party’s definition of “natural.”
The very nature of the origin and composition of colorants renders them susceptible to the types of natural processes that lead to instability in food applications. Light, heat, oxidation, enzyme activity, pH, and interactions with other components of food formulations all are factors that can contribute to the challenges associated with the use of natural food colorants.
Natural colorants are normally thought of as less stable than their synthetic counterparts. While this generally is true for most natural colorants, it is not the case for all of them. The chemical nature of the coloring compounds plays a critical role in determining the stability and utility of these natural products.
There are a number of gaps in the palette of available natural shades. While there are certain limitations in the synthetic colorant palette, they are nowhere near as manifest as in the natural colorant palette. Ideally, given the inertia that has developed over the last few decades for the use of relatively inexpensive, broadly useful, easily applied, and relatively stable synthetic food colorants, the industry would prefer to have one-for-one replacements in the natural toolbox.
Under pressures from the aforementioned strong consumer drive to eliminate synthetic ingredients, food scientists and food manufacturers are faced with the challenge of making naturally derived coloring materials work. Moreover, these materials must work within formulations in which other ingredients, perhaps synergistic with color, also have been removed.
A number of naturally sourced colorants are available in other global markets but not in the US. Most food product developers and manufacturers, as well as marketers, food scientists, and regulatory specialists, are well aware of this fact. Some of these colorants are approved for use in the EU; some only in markets such as Asia.
Natural food colorants are extracted from the gardenia plant (Gardenia jasminoides). Its major coloring compound is crocin, but iridoid and flavonoid coloring compounds also are produced in the plant. Interestingly, crocin (along with crocetin) is a primary coloring compound in saffron, which is permitted in the US. Gardenia yellow is approved for use throughout Asia, and it is commonly used in many applications. For instance, in China higher quality instant noodles are frequently colored with gardenia yellow.
Gardenia colorants are particularly interesting because of their versatility and color range. Gardenia yellow is extracted from the fruit of the gardenia plant in much the same way that hibiscus color is extracted from hibiscus flowers. Moreover, it is possible to convert the yellow color to red, green, and blue gardenia colorants through an enzyme-modification process using natural, food-grade enzyme preparations in the presence of amino acids. These products are water-soluble and maintain good stability in the presence of heat, light, or low (acidic) pH.
Safflower yellow is a bright yellow-to-reddish colorant permitted for use in food in Asia and Europe, but not in the US. The safflower plant itself, Carthamus tinctorius, is grown mainly for its seeds, used to produce an edible oil. The fruit of the plant is extracted to yield three primary colorants, Carthamin, Safflor Yellow A, and Safflor Yellow B. Safflower Yellow is a suitable replacement for FD&C Yellow #5.
Turmeric has become one of the preferred natural yellow colorings of late and is becoming widely used in the US as a replacement for Yellow No. 5. But turmeric oleoresin is notoriously unstable in direct light. For this reason, its applications are severely restricted. Moreover, the coloring agent in turmeric oleoresin (curcumin) is not naturally water-soluble, and is even barely soluble in oil. This means it must be formulated with an emulsifier for applications in water-based systems.
Typically, emulsification of turmeric coloring has been accomplished with food-grade emulsifiers such as polysorbate-80. Polysorbate-80 is a highly functional, synthetic emulsifier that raises clean-label issues. Safflower yellow, however, is water-soluble and relatively stable to pH, light, and heat. Efforts are underway to obtain approval of safflower yellow in the US, and some experts believe that could happen as soon as the end of this year.
Like Red on Rice
Red yeast rice is a colorant obtained from a fermentation of rice by the Monascus purpureus mold. It is permitted for coloring food throughout Asia but not in Europe or the US. (It is, however, an approved nutritional supplement in the US.)
Traditionally, the fermented rice has been eaten as a colorful novel food. It also is used as part of traditional Eastern medicine to treat symptoms of hypertension.
Historical preparation methods were known to produce an antibiotic compound that was considered undesirable in food ingredient preparations. This concern has been eliminated through modern production methodologies.
The coloring agents structurally are similar red and yellow compounds. Monascus coloring preparations can be used to impart a red color suitable as a replacement for FD&C Red #40 in some applications. It demonstrates good stability to heat under neutral pH conditions but will fade upon prolonged exposure to light.
Carbon Black is essentially soot collected from the burning of vegetable matter. It gives a natural true-black color and has been used in a limited number of food applications, such as licorice, for many years in the EU. Although once permitted in the US, it has been banned for years in the US, as has yellow from safflower.
True Blue…and Green
Chlorophyll is found abundantly throughout nature as the green color characteristic of photosynthetic plants. In its natural state, chlorophyll has a porphyrin ring structure that is associated with a magnesium ion (Mg) bound in the central receptor location. In this state, chlorophyll extracts produce a bright green color in many food and beverage applications, although with limited stability.
When the Mg ion is removed from chlorophyll, the resulting structure is called pheophytin, which has a less vivid, olive-green color. If the pheophytin is further processed, and the Mg ion is replaced with a copper (Cu) ion, the result is a brighter, more vivid and more stable green color. This compound is called sodium copper chlorophyllin. The chlorophyllin variation is currently permitted for limited use in the US market, although restricted to dry citrus beverages.
Since stable, natural green colorants are rare, chlorophyllin potentially could fill a much larger role in the coloration of prepared foods. Chlorophyll colorants are more broadly permitted for use in the EU, where they are produced by extraction of permitted plant materials, mainly alfalfa.
Spirulina extract as a colorant is relatively new to the US market. It is derived from the edible algae from which it gets its name, and, as a whole cell preparation, it has been used as a food and as a dietary supplement for decades. It is derived from the blue-green, edible algae from which it gets its name. (There are two main species, Arthrospira platensis and Arthrospira maxima.) As a whole-cell preparation, spirulina has been used as a food and a dietary supplement for decades.
Spirulina is one of the few natural blue colorants that has attained approval for use in foods and beverages in the US. Extracts that isolate the blue phycocyanin compounds may be used by themselves to impart blue colors, or in combination with naturally derived yellow colorants to achieve shades of green. Examples include turmeric oleoresin, beta-carotene, safflower extract, and yellow gardenia. Spirulina is reported to be broadly useful and relatively pH- and heat-stable in applications where water activity is relatively low, such as confectionery.
A fruit juice blend combining watermelon and huito fruit from the Genipa americana plant has been available in the US for a few years. Huito is a rain forest native that flourishes from southern Mexico into South America and the Caribbean. The juice blend is used to contribute blue colorings to beverage, confectionery, and other applications. It is reported to be heat-stable and stable within a pH range from 2.8-8.0.
While these useful colorants are available in other regulatory jurisdictions and could help plug gaps in the color palette available in the US and the EU, a deeper look reveals possible advantages where performance is concerned. The difficulty, although manifested differently for each compound, is getting them approved for use in this country.
In the US and EU, food colorants are strictly regulated. This is a practice with roots in history and consumer protection. At the turn of the 20th century, as processed foods were beginning to have an impact on the lives of everyday people, it became apparent that, without some constraints, processed foods could become an unregulated experiment on unsuspecting consumers. From the industry perspective, if consumers could not trust the safety of processed foods, there would be no processed food industry.
A major challenge in the processed food and beverage industry is the need for consistency. Consumers see consistency in visual appearance of products as an indicator of purity and trustworthiness regarding those products and their ingredients. Nevertheless, natural foods have natural—yet perfectly safe—variations in their appearance.
While such natural variation has no impact on the quality of the finished products, it can cause a consumer to question the quality of the product. When annatto is used to color cheese (such as Cheddar, Colby, and Red Leicester), the natural variations are masked, and the product appears uniform over the course of the year. When beta-carotene is added to butter, the effect is not only a uniform color across the seasons, but also fortification with a vitamin A precursor.
Against this historical backdrop and with an overriding mandate for consumer safety, the industry and its regulators face some important new challenges. These include a strong consumer demand for clean labels and natural ingredients, often in the absence of clear definition or scientific support; a frequently inaccurate perception that many of the ingredients and additives commonly in use are “chemicals” and therefore are dangerous or undesirable; a willingness on the part of consumers to accept the increasingly frequent and often unsubstantiated claims of safety concerns; and the fundamental difficulty of determining with certainty the safety of almost anything.
Is It Safe?
The fundamental basis for determining the safety of a color additive is the feeding study. Test animals, divided into control and test categories, are fed the color additive in question with their normal food and/or water intake at a rate that can then be translated into an acceptable intake for a human being.
Safety factors are used to account for the likely variation in effect between the test animal (usually rats) and humans. These factors attempt to account for the dose effect and other variables that cannot be easily quantified. The ultimate goal is to assign a usage level that is safe for human consumption.
Under such conditions, the test animals often are subjected to inordinately high doses of the colorant being tested, so much so that their food supply may be rendered nearly or entirely unpalatable. Yet this type of study is the only means available to make a scientific assessment of the safety of any food colorant that is to be permitted for broad application in foods and beverages.
After evaluation of the available evidence, a decision can be made regarding the additive’s general safety and the risk to the consuming public. The formal submission to the FDA is known as a Color Additive Petition (CAP).
The role of the regulators is clearly defined in principle: Protect the consumer by ensuring that the food supply is safe. The degree to which the food supply can be considered safe depends on a number of factors, including opinion. Substantial ambiguities exist—not in the mission, but in how it is defined and executed. At minimum, the regulating authority must apply a set of performance standards designed to guarantee that a color additive is safe for human consumption.
The process of evaluating and establishing the standards is long and arduous, mainly because consensus must be achieved among the many stakeholders. This includes food growers and manufacturers, food sellers, the consuming public, those who write the legislation, and those who must perform the activities necessary to uphold the standards.
An example of the process facing a new (for the US) colorant is the use of red beet in this capacity. This is a commonly known vegetable, still consumed in the US, Europe, and Asia. The principal colorant in red beet is the betacyanin compound betanin. Betanin, and minor amounts of related compounds, give beet juice its intense red color.
At one time, consumption of red beet juice was considered a potential health problem due to its relatively high content of nitrates and nitrites. Nitrites were thought to contribute to the formation of nitrosamines, potentially toxic substances that generated a good deal of concern a few decades ago.
Today, beet juice is considered a health food because it contains naturally occurring nitrates. A biochemical cascade of reactions in the body convert the nitrate into nitric oxide, believed to improve blood flow; help to lower blood pressure; and increase stamina during exercise.
If a standard, edible cultivate of red beet is grown, harvested, and processed to make a concentrated juice, then it is permissible in the US, EU, and Asia to use as a food colorant. Standard beet cultivars are relatively low in colorant content, and they contain other plant substances, including sugars.
The processing normally includes washing, slicing, crushing, and pressing to release the juice, then filtration and concentration to maximize the color content per unit weight. The concentration step involves removal of water, and the sugar content of the juice sets a limit on how much the juice can be concentrated.
Over the past few decades, strain-selection methods have been shown to be effective for dramatically increasing the level of betanin that is produced by the beet root. In addition, the production of sugar is reduced, allowing for more efficient and extensive concentration of the expressed juice. This process makes the selected cultivar more economical for colorant production, but renders the beet itself less palatable because of the reduced sugar content.
In recent years, a new category of naturally derived food colorant has arisen, called the “coloring food.” This is not a new regulatory category but, rather, an informal classification defined under guidance offered by EU authorities.
The basic premise is that if a food has coloring properties—for example, red beet—then it should be allowed in food products without a requirement that it be labeled as an additive. Thus, in the EU, it could be used without being labeled with an “E” number. Recently, guidance has been offered as to what level of processing may be permitted while still allowing the item to retain an identity as a food that colors, rather than as an ingredient or additive.
Thus, in the EU, it could be used without being labeled with an “E” number. Recently, guidance has been offered as to what level of processing may be permitted, while retaining an identity as a food that colors, rather than as an ingredient or additive.
In such a case, the red beet could qualify as a functional food colorant from an edible source. However, if the original beet is processed too much, it could be considered no longer a food but a chemical to be regulated. Simply harvesting the beet, expressing the juice, filtering it, and then removing water to concentrate could be considered gentle enough treatment so that the colorant is still a good, wholesome vegetable juice.
Hypothetical challenges to regulation in this category could be, for example, to inoculate beet juice with a bacterial strain to ferment the sugars so that the juice could be concentrated for color more effectively. However, the question remains: At what point does the identity of a beet (or other source) change to an unacceptable level?
As analytical methods become more sensitive, and as food scientists uncover more about the chemical nature of natural color ingredients, many questions arise. Such issues as what standards should be used; how detailed they should be; and what limits must be set are among the questions that become increasingly important to address. On a positive note, interested color makers are pushing the boundaries to bring more natural food and beverage color options to the industry.
Originally appeared in the February, 2017 issue of Prepared Foods as Color Outside the Lines.