Color is arguably the most important initial sensory cue we get from a food or beverage. It helps us almost immediately make a preliminary judgement about the desirability, quality, and palatability of what we plan to eat or drink. If the color of an item is “wrong” or off, it can drive the consumer away from even the tastiest treat.
It even is possible to be fooled by color into thinking that one is tasting a flavor that isn’t there. For example, a mango purée that’s dyed a natural bright red and labeled as strawberry purée can be perceived as tasting of strawberries, or an orange-colored, lemon- flavored lollipop could easily be mistaken for an orange-flavored one.
Red is one of the most eye-catching and impactful of colors. This is true even outside of food and beverages — think of lipstick and rouge, or a Ferrari, or even a stop sign. However, when it comes to food, red can deliver multiple messages: It is an indication of identity, ripeness, flavor, variety, and palatability in fruits like apples, strawberries, raspberries, cherries, and tomatoes.
Red can characterize the flavor of otherwise colorless preparations, such as beverages. For decades the food and beverage industry relied heavily on synthetic food dyes to deliver red colors. They work well, perform consistently across a range of applications and conditions, and are inexpensive to use. However, as consumers continue to become more discerning in their choices of what they consume, they increasingly seek ingredients categorized as natural. Nowhere has this drive been more comprehensive than with food colors, and no food color has been subjected to the most intense efforts to “go natural” more than red.
Carmine is the poster child for this effort. It is a highly stable red food colorant that works well in most applications and has been used in food and as a fabric and cosmetic dye for centuries. It maintains superior stability under heat, light, and oxidative conditions. This made it a desirable natural colorant from the perspective of food manufacturers. It even is categorized as a natural colorant (Natural Red #4). However, in recent years carmine has received a flood of negative attention because it is derived from an insect, specifically the Armenian cochineal beetle (Porphyrophora hamelii).
While the extraction and processing of cochineal-derived colorant results in a highly purified concentrate, and thus is no different in that chemical respect as are many natural colorants, the source is off-putting to many consumers. It has also been linked to an extremely low incidence of allergic reaction among some consumers. Put simply, while the vivid red of Natural Red #4 doesn’t fade, its popularity is rapidly doing so.
AU NATUREL
Luckily, with the color red, nature offers an array of sources, although some might not be as obvious to consumers. (Also, those that might seem obvious are not: As an example, it is could be assumed that it’s possible to obtain a viable red color from apple peels — and it is. Doing so just is not commercially viable from a cost perspective to do so.
Grape skin, on the other hand, has been a commercially useful food colorant, in certain applications, for decades. Grape skin extract is just one example of the class of colorants known chemically as anthocyanins. This source can provide a spectrum of colors from rose to red to purple.
Anthocyanins are highly water soluble, not oil soluble, and work best at low pH. As the pH rises, and depending on the anthocyanin, the color will change from bright red to violet or blue. This makes anthocyanin colorants highly suitable for use in acidic beverages, juices, candies, jams, jellies, other types of fruit preparations, and similar applications. Depending on the anthocyanin, one can obtain red color shades with either blue or yellow tones.
Other popular sources of anthocyanin colorants include red cabbage, elderberry, purple sweet potato, black carrot, and red radish. These exhibit similar sensitivities to pH conditions, but where grape skin extract can begin to shift from red to violet at around pH 3.5, other anthocyanins, especially red radish, can be used at pH levels approaching 6.0.
Ripe tomatoes exhibit a lush red color caused by lycopene, a carotenoid in the same chemical family as beta-carotene. Lycopene derived from tomatoes has become a more reliable food colorant, and in the past couple of decades, technologists have been increasingly successful at plumbing its benefits.
Today’s lycopene-derived colors — which range from pale gold to deep vermilion — have higher stability and clarity than ever and can be used across more applications. Scientists continue to improve on methods for enhancing and supporting their functionality. Moreover, they have developed processing techniques that allow synergistic formulating with other food ingredients to enhance that functionality.
Lycopene colorants are used successfully in a variety of applications. Lycopene itself is oil-soluble, and in oil media it gives a yellow color, as do other carotenoids such as annatto (which also can provide colors ranging from gold through deep orange to red) and the aforementioned beta-carotene. In nature, the tomato produces lycopene within its cells in crystalline form. It is the crystalline form gives the red color, and that crystalline form that must be maintained to deliver a desirable red shade.
The processing and formulating methodologies that have moved lycopene to the forefront of natural red through increasing stability are based on preservation of the crystalline state. As food scientists have become more aware of that and developed new technologies to effect it, the range of uses of lycopene as a food colorant has increased substantially.
Another commonly used natural red colorant comes from red beet juice. Beetroot red is a betalaine that is produced in the red beet root (Beta vulgaris). This well-known natural red colorant also has experienced concerted efforts to bolster its range of expressed shades, stability, and shelf life so that it can be used in a variety of food preparations. It is not as sensitive to pH as the anthocyanins, so it can be used across the pH range of most food products (2.5 to 7.0). It is, however, sensitive to heat in many cases, which can limit its utility.
REFINING HUES
Food and ingredient scientists are always seeking something new, whether an ingredient or a technique, usually to solve a performance problem or satisfy a marketing demand. Much of the development work on natural red colorants over the past several years has been focused on finding ways to extend their working pH range, heat stability, or light stability. New sources have been proposed, but the approval process in the US is long and complex, unless the source is a known and commonly consumed fruit or vegetable.
The useful pH range of anthocyanins can be extended by choice from the existing palette of fruit and vegetable juice-based products. The color shades vary from source to source, but the colors produced can be vibrant and eye-catching. At low pH ranges (2.5 to 3.5), most anthocyanins will yield bright red colors and exhibit good heat and light stability. The stability of some simple anthocyanins can be increased in some cases by using specialized food ingredients that act as intermolecular co-pigments. These ingredients form a complex with the anthocyanin and protect it from conditions that would otherwise shorten the life of the color.
Most anthocyanin sources are produced in their respective plant sources with co-pigments attached to the anthocyanin structure, so they have their own intramolecular co-pigment protection. The choice of source might come with slight changes in hue, but it also extends the useful pH range and the color’s resistance to discoloration by heat and light.
Carotenoid colorants such as lycopene can be protected against heat, light, and oxidation by using natural antioxidant ingredients that are sacrificially consumed to protect the carotenoid colorant. These include the de-flavored extracts of herbs, such as rosemary and vitamin E (in its tocopherol form).
The use of otherwise oil-soluble carotenoids can be extended by creating emulsions or colloidal suspensions with the assistance of naturally occurring surface active agents, such a gum Arabic or gelatin. Microencapsulation is another way of protecting and water-solubilizing the lipid-based colorant.
