Color Perception and
Measurement
Foods / Biomaterials
Color
• Important physical property
• Determines acceptability of a food by a
consumer – quality attribute in food, does not
necessarily reflect nutritional, flavor, or functional
values
• Variety of systems used to describe color
• Color order systems are 3-dimensional
arrangements of color according to appearance
– 5 color order systems for food
Tempting Vision thru Color
• It’s not a secret that the way food looks has an effect on our
willingness to eat it. That’s why top chefs spend so much time
perfecting the presentation of their plates, and food companies
spend so much money on marketing and packaging. Of course,
taste is the most important sense when it comes to enjoying food,
but just how important is sight?
• Try this thought experiment: a bowl of yellow-colored gelatin is
placed before you. How would you expect it to taste, sweet or sour?
It could be that you think it will taste sour, because of your prior
experience with other yellow foods that are sour, such as lemons
and grapefruits. Or you could think it will taste sweet, based on your
memory of other sweet foods that are yellow (like bananas or
pineapple).
Color Basics
• Color is the perceptual characteristic of light described
by a color name. Specifically, color is light, and light is
composed of many colors—those we see are the colors
of the visual spectrum: red, orange, yellow, green, blue,
and violet. Objects absorb certain wavelengths and
reflect others back to the viewer. We perceive these
wavelengths as color.
• A color is described in three ways: by its name, how pure
or desaturated it is, and its value or lightness. Although
pink, crimson, and brick are all variations of the color
red, each hue is distinct and differentiated by its chroma,
saturation, intensity, and value.
Things required to see Color
• A light source / illuminant
• An object
• An Observer
• Color of a material becomes visible only when
light from a luminous object or source
illuminates or strikes the surface
• Chroma, intensity, saturation and
luminance/value are inter-related terms
and have to do with the description of a
color.
• Chroma: How pure a hue is in relation to
gray
Saturation: The degree of purity of a hue.
Intensity: The brightness or dullness of a
hue. One may lower the intensity by
adding white or black.
Luminance / Value: A measure of the
amount of light reflected from a hue.
Those hues with a high content of white
have a higher luminance or value.
Chroma
Intensity
Shade
Tint
• Shade and tint are terms that refer to a
variation of a hue.
• Shade: A hue produced by the addition of
black.
Tint: A hue produced by the addition of
white.
Color measurement
• Used if a correlation is present between
colored component and chemical in food
• Simpler and quicker than chemical
analysis
• Color changes occur in products during
storage, maturation, processing, spoilage
– potato chips
• Color used to determine ripeness of fruits
Spectral Quality
• Natural daylight varies greatly in spectral
quality with direction of view, time of day
and year, weather and geographical
location
• Simulated daylight is commonly used in
industrial testing
• Artificial light sources can be standardized
and remain stable in quality
Measuring Color
• Our perceptions and interpretations of color are highly subjective.
Eye fatigue, age and other physiological factors can influence your
color perception.
• But even without such physical considerations, each observer
interprets color based on personal references.
• Each person also verbally defines an object's color differently.
• As a result, objectively communicating a particular color to someone
without some type of standard is difficult.
• The color of many products acts as an important indicator of product
quality and processing performance. There also must be a way to
compare one color to the next with accuracy.
• The solution is a measuring instrument that explicitly identifies
a color. That is, an instrument that differentiates a color from all
others and assigns it a numeric value.
How to Measure Color
• Color Measuring Equipments
– Spectrophotometers
– Colorimeters
Spectrophotometer
• Today, the most commonly used instruments for
measuring color are spectrophotometers.
• Spectro technology measures reflected or
transmitted light at many points on the visual
spectrum, which results in a curve.
• Since the curve of each color is as unique as a
signature or fingerprint, the curve is an excellent
tool for identifying, specifying and matching
color.
Colorimetry
• Colorimetry, the science of color measurement,
is widely employed in commerce, industry and
the laboratory to express color in numerical
terms and to measure color differences between
specimens.
• Applications include paints, inks, plastics,
textiles and apparel, food and beverages,
pharmaceuticals and cosmetics, displays, and
other parts and products that reflect or transmit
color.
Colorimetry
• The use and importance of colorimetry has grown in
unison with the increase of global manufacturing and
processing. When plastic automotive trim produced on
one continent, for example, must match a painted metal
finish applied on another, an objective and precise
description of color becomes an absolute necessity.
• Unfortunately, human color perception varies widely and
is affected by illumination, sample size, surrounding
color and the angle of observation. Colorimetric
instruments provide a set of standardized conditions that
help assure consistency and repeatability.
Use of Color
Specifically color is used in industry such as for:
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Quality Control
To check on contamination or degradation As an indication of suitability for a
particular purpose As a guide to the condition of used product
Refining
As a measure of progress in refining and processing Feedback for process
control and optimisation Identification of product grade
Materials Sourcing
An immediate guide to supply continuity
Inspection of Incoming materials
Assurance that materials meet color specifications
Production Control
A check for consistency within and across batches
Inspection of final products
Conformance to predetermined color tolerances Compliance with customer
specifications
ASSIGNMENT
Color Order Systems
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Munsell
CIE
CIE L*a*b* (CIELAB)
Hunter Lab
Lovibond