Color Quality of Fresh and Processed Foods - American Chemical

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Communicating Food Color Effectively with Physical Color Standards Downloaded by MICHIGAN STATE UNIV on February 14, 2015 | http://pubs.acs.org Publication Date: June 13, 2008 | doi: 10.1021/bk-2008-0983.ch001

Arthur C. Schmehling GretagMacbeth LLC, 617 Little Britain Road, New Windsor, NY 12553

When working with color it is possible to define a color instrumentally for repeatable and consistent production of that color. But, there are times when an instrumental measurement is not possible and it becomes necessary to use a physical color standard for evaluation and comparison purposes. Physical Standards are a cornerstone of any good color program and they allow for the ability to specify and communicate a specific color accurately. This paper will go into the aspects that it takes to manage and create physical color standards to effectively communicate color in a global environment.

A few years ago, a leading ketchup producer developed several specialty colors to appeal to kids. While kids loved them, adults had mixed reactions. One might expect purple ketchup to taste differently than conventional red ketchup - however, it did not taste differently at all. One is "taught" to expect a certain taste or flavor based on color. We associate red with sweet strawberries and yellow with sour lemons. We also associate a shift in color as potentially negative. For example, several bottles of red ketchup on a retail shelf with differing shades of red might indicate that some of the bottles have been on the shelf for a long time and perhaps are not as "fresh" as the other bottles. When the expected color changes, our perception also changes.

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© 2008 American Chemical Society

In Color Quality of Fresh and Processed Foods; Culver, C., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2008.

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Downloaded by MICHIGAN STATE UNIV on February 14, 2015 | http://pubs.acs.org Publication Date: June 13, 2008 | doi: 10.1021/bk-2008-0983.ch001

Color management programs ensure quality In grading and packaging food products color often indicates quality. Therefore, a color management program is necessary not only for economic reasons, but also for brand quality and standardization. An important part of a color management program includes the use of physical color standards to communicate color and establish acceptable visual deviations. This is especially important in the food industry where the colors of organic ingredients change quickly with time, temperature and light. Physical color standards are also essential for industries where the value of the product is determined by grades of color. Failure to accurately assess color could have a significant economic impact. Color management involves the product cycle from grading and sorting to processing and production. Each of these phases can have a profound effect on the color of the final product. Establishing an effective color management program utilizing physical color standards requires an understanding of basic color principles.

Basic color principles - the foundation of color management The three components required to see color are: (1) light source, (2) object, and (3) observer. An effective color management program considers how these three components can be controlled or monitored so that they do not adversely affect color evaluation.

Light source All color is created from the interaction of light energy with an object that either reflects or absorbs the light, which is then viewed by an observer. The light source is controlled by using a standardized lighting product, such as a SpectraLight® light booth or Examolite® overhead fixture that meets industry guidelines for color evaluation (ASTM D1729 (7), ISO 3664 (2), SAE J361 (5), DIN (4), ANSI (5) and BSI (6)). Standardized lighting usually involves color evaluation under daylight and at least one other light source, such as cool white fluorescent or incandescent. One's color perception can change dramatically based on the lighting condition. Standardized lighting simulates the environment under which various food products will be evaluated, such as noon sky daylight or a typical retail environment, such as fluorescent. Some retail environments require a light source that enhances food color. For example, grocery stores often illuminate the meat department with a lower color



4 temperature, higher red energy light source to enhance the red tones in fresh meat. The way in which each light source renders color is based on the energy present in the light source at each wavelength. This is characterized as the spectral power distribution (SPD). The SPD for daylight at D65, with a Color temperature of 6500 Kelvin, indicates more evenly balanced amounts of spectral energy (red, orange, yellow, green, blue, indigo, and violet - commonly referred to as ROYGBIV). It is for this reason that daylight at D65 is often the primary light source under which products are evaluated. Cool white fluorescent, on the other hand, has a SPD that spikes in the blue and green regions of the spectrum. This excess of blue and green energy tends to dull the appearance of red and is typically used as a secondary or tertiary light source to simulate color rendering in a retail environment.

Observer Aside from perceptual differences in the way we interpret color, observers must be tested for physiological conditions, such as color blindness, which may prevent an observer from accurately evaluating color. Additionally, certain physiological differences may not completely undermine one's ability to evaluate color, but may hamper one's ability to discriminate between colors. For example, one observer may be less able to detect color shifts affecting red colors as opposed to green. A simple 15-minute test, known as the Farnsworth Munsell 100 Hue Test, will indicate the degree to which one is able to discriminate color, in addition to ruling out color blindness. The Farnsworth Munsell 100 Hue Test meets the industry guides for use in evaluating the color vision of an observer as mentioned in ASTM D-1729 and D-1488 (/) for establishing visual color evaluation procedures. Screening of personnel who will be performing visual assessment of color is an important and often overlooked step when developing an effective color management program.

Object As discussed previously, physical standards establish an ideal color and the acceptable variation in color. This is of crucial importance to the food industry, where the color of various ingredients can change based on environmental conditions. While instrumental measurements from a spectrophotometer monitor color digitally, often a digital standard is not practical for use in certain parts of


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the process. For example, grading or sorting freshly picked produce is more easily accomplished with a standard light source, physical standard and an evaluator with good color discrimination, than by measuring the sample on a spectrophotometer on site. Many color management programs incorporate the use of spectrophotometric measurements, in addition to the physical samples, for detailed color analysis. This is more practical in a laboratory setting and still requires the use of a physical standard to establish benchmark colors.

Developing a physical color standard When developing a physical color standard, it is important to identify the state in which the sample will be evaluated - for example, liquid or solid - and the properties such as fine or coarse powders, opaque or translucent solids or liquids, etc. This is the basis for developing a standard that is representative of the material being evaluated. Today's physical standards can be produced from a wide range of materials that allow more flexibility in evaluating a sample. For example, a washable standard allows fluid samples to be poured directly on the standard for more accurate evaluation, instead of potential color distortion caused by a beaker. Physical standards also simulate physical characteristics of the material being evaluated such as translucency, gloss, and texture. A physical standard may represent a single acceptable color or several color variations or tolerances within a given process. Some process variation is unavoidable, and color tolerance standards allow one to manage the deviation to an acceptable visual level, and reduce waste or downgraded product. An acceptable visual level is determined based on lightness-darkness, saturation (intensity) and hue shift. In industries where grading is required, it is necessary to develop a color scale. Colors on the scale correspond to the grading system and ultimately help determine the product's value. The standards development process itself must be tightly controlled and repeatable. Color formulations are derived from the least number of colorants that will produce an accurate match. This eliminates metamerism (a set of colors which match under one light source and not under another) and ensures a more repeatable process. Additionally, a documented system of controls must be implemented. All color standards have a shelf life. Therefore, expiration dates, part numbers storage conditions, etc. must all be documented for tracking and certification purposes.


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Use of physical color standards Accurate physical color standards can provide the closest representation of the ideal sample. In some cases, this is the only means for quality control and production personnel to see the actual color target and provide adequate visual evaluation of samples. Physical color standards not only help control the final product, but also the steps within a process. For example, a certain beverage is assessed following the pasteurization process. Unacceptable shifts in color may indicate out-of-control process variables such as temperature or cooling time. When physical color standards are produced within a tightly controlled process as described previously, they enable effective color communication across a large manufacturing or supplier base. The use of physical color standards in a color management program complements instrumental color control processes. The human eye remains the final arbiter of color, and therefore, visual evaluation in conjunction with instrumental evaluation provides a comprehensive and effective color management program.

Conclusion Physical color standards are an important part of a color program. Developing accurate physical color standards requires an understanding of basic color principles applied to a tightly controlled process. While physical color standards enable the flexibility to work within a variety of production and manufacturing processes, their effectiveness is optimized when integrated with instrumental color control and a controlled viewing environment.

References 1. 2. 3. 4. 5. 6.

ASTM International Home Page. http://www.astm.org (accessed Mar 11, 2007) International Organization for Standardization Home Page. http://www.iso.org (accessed Mar 11, 2007) SAE International Home Page. http://www.sae.org (accessed Mar 11, 2007) Deutsches Institut für Normung Home Page. http://www2.din.de (accessed Mar 11, 2007) American National Standards Insititute Home Page. http://ansi.org (accessed Mar 11, 2007) BSI Home Page. http://www.bsi-global.com (accessed Mar 11, 2007)


Color Quality of Fresh and Processed Foods - American Chemical

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