Measuring Food Color

Food processors use food colors to optimize the attractiveness, appeal, and presumptive appetizing features of foods to the consumer.

Colors serve as a code to identify certain foods, such as candy flavors. A green color usually is associated with a lime flavor, a yellow color with a lemon flavor, and a black color with a licorice flavor. However, it is possible for processors to technically color a food with a normally associated color, but add a different dominating flavor. This is usually reserved for experimental testing or “fun foods,” but processors should recognize the benefits of providing their customers with every means of satisfaction from food flavors, including anticipated flavors recognized through color identification.

Archaeologists date cosmetic colors as far back as 5000 B.C. Early Romans have documented that people “ate with their eyes,” as well as their palates. Saffron and other spices were often used to provide a rich yellow color to foods. Butter has been colored yellow as far back as the 1300s.

Color Additives
Color additives today are strictly regulated by the Food and Drug Administration to ensure that they are safe for addition into foods. Technically, a color additive is any dye, pigment, or substance that can impart color when added or applied to foods, drugs, cosmetics, or the human body. FDA separates food color additives into two categories: “certified” and “exempt from certification.”

Certified colors are man-made (derived primarily from petroleum and known as coal-tar dyes), with each batch being tested by both the manufacturer and FDA. This “approval” process is known as color additive certification, which assures the safety, quality, consistency, and strength of the color additive prior to use in foods. Each color has chemical “specifications” that place restrictions on the levels of impurities allowed and ensure that the color contains no cancer-causing substances. FDA scientists use chromatography and other sophisticated analytical techniques to analyze the color additives.

In 1900, there were about 80 man-made color additives available for use in foods and no regulations. The Pure Food and Drugs Act of 1906 listed only seven of these as approved for use in foods. The Federal Food, Drug, and Cosmetic (FD&C) Act of 1938 tightened certification, and the 1960 Color Additive Amendments to the FD&C Act placed color additives on a “provisional” list and required further testing. In addition, the Nutrition Labeling and Education Act of 1990 required certified color additives used in foods to be listed on the label ingredient statement. Today, there are nine certified color additives approved for use in the United States, with seven of them permitted in food manufacturing. An example of a certifiable color additive is FD&C Yellow No. 6, which is commonly used in cereals and bakery goods.

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Color additives that are “exempt from certification” include pigments derived from natural sources such as vegetables, minerals, or animals, and man-made counterparts of natural derivatives. An example of the former is caramel color, which is produced by heating sugar and other carbohydrates under controlled conditions; it is used in gravies, soft drinks, baked goods, and other foods. Another example is orange annatto, which is widely used for color in cheese.

Synthesis of anthocyanidins offers a compound for use as a yellow-colored food dye. However, despite their satisfactory yield and wide color control attributes, anthocyanidins will require extensive safety testing because they are not natural products.

Additional information regarding color additives can be found on FDA's Web site at http://vm.cfsan.fda.gov/~lrd/colorfac.html and http://vm.cfsan.fda.gov/~dms/cos-221.html.

Color Measurement Methods
According to Oregon State University's Food Resource Web site (http://food.oregonstate.edu), the most frequent use of food color measurements is related to developing objective indices of food quality. Sensory attributes of food related to appearance are the most susceptible to objective measurement. Generally, there are two categories of appearance: color attributes related to the wavelength distribution of light, and geometric attributes related to special distribution.

Worldwide literature reviews have indicated that there has been a lot of use of the theory of color in both areas of foods, yet there is a lot still not known or understood. The basic concept that must be stressed is that color specification of a material is simply the specification of a point of three-dimensional space. This space, regardless of whether it is visual or mathematical, has become known as a color solid. One of the earliest and most successful attempts to develop a visual color solid was that by A.H. Munsell in the early 1900s. Other early pioneers in color measurement included Judd, who developed the Uniform Chromaticity Scale (UCS System) in 1935, and Hunter, who developed the Hunter System in 1942.

The color theory is based on light's being made of red, blue, and green colors. Although there are almost as many colorants and color components as there are chemical compounds, they can all be classified into major categories. For example, browns or blackish colors can be the result of either enzymatic or non-enzymatic reactions. A major non-enzymatic reaction of interest to food scientists is the Maillard reaction, which is a dominant browning reaction. Others of interest are caramelization, the enzymatic browning reaction widespread in fruits and vegetables, water-soluble pigments categorized as anthocyanins and anthoxthanins, fat-soluble plant pigments in chlorophyll and carotenoids, and myoglobins in meats.

Procedures for analyzing natural and synthetic carotenoids as colorants may require extraction and purification, high-performance liquid chromatography, UV-visible light absorption spectroscopy, quantitative determination, and other physicochemical methods. The current listing of approved certified colors has resulted from many industry and regulatory agency tests, including live animal studies. Based on the time and cost involved with conducting new animal studies, it is unlikely that this method will be used to adopt previously rejected or new colorants. It is more likely that advances in toxicological methods will enable scientists to assess potential hazards of colors and other food additives through a series of short-term test-tube tests.

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What Suppliers Recommend
I asked several suppliers of food colors and color measurement equipment or methodology what they recommended that food processors consider as options in their selection of food color additives for their food products. The following replies were offered.

Hal Good, Director of Marketing Services for HunterLab, Reston, Va. (phone 703-471-6870, www.hunterlab.com), a major supplier of color measurement equipment, said, “Color is an important attribute to the food industry. Consumers frequently look at a food product and make a decision largely based on overall appearance, including color. This is why color measurement systems are used within the food industry for R&D, process control, and quality control. Processes such as extrusion, cooking, frying, and baking, as well as ingredient color, storage methods, and time, can affect final product color. Thus, to obtain and maintain the desired color, it is important to monitor and control ingredient color, as well as monitor the product through the manufacturing process.”

Good said that color measurement is done for several reasons: to determine ingredient effect on product color; determine color change as a result of storage, processing, and other factors; ensure consistency of the color ingredient; determine conformance to final product specifications; and grade final products.

He described HunterLab's wide range of instruments and sample-handling devices designed to measure specific types of food samples. The ColorFlex^® and LabScan^® XE are ideal, he said, for measuring opaque and translucent solids and liquids in the form of solids, pastes, powders, and small granules; these include flour, sugar, powdered drinks, milk, cheese, meat, spices, tomato juice, orange juice, jams, soups, sauces, and custards. The D25L-9000 measures coarse granules, flakes, chips, and disks, including fruit, crackers, cookies, cheese puffs, and coarse cereal. The ColorQuest^® XE measures transparent samples, including clear juices, wines, jellies, gelatins, vegetable oil, soft drinks, and brewed tea; it can also measure transmission haze. The ColorTrend^® HT is mounted directly over a moving band to provide continuous process control measurement of baked and fried products.

Owen Parker, Vice President-R&D, D.D. Williamson & Co., Inc., Louisville, Ky. (phone 502-895-2438, www.caramel.com), a major supplier of caramel coloring, said that his company uses the Food Chemicals Codex (FCC) method for analyzing color. Caramel color, he said, like so many other colors used in the food industry, is manufactured at high concentrations and used in small concentrations. “This being the case,” he said, “our methods reflect this, and our specifications are directed toward a finished product concentration. The FCC states that you use a dilution of 1 g/1,000 mL of distilled or deionized water, and then measure color on a spectrophotometer at 610 nm. There are many other methods for looking at color, but this is our standard.

by DEAN DUXBURY
Contributing Editor
Consultant, Oak Brook, Ill.
[email protected]