Color is in the eye of the beholder

July 3, 2007

In some regions of Central Europe, salad dressing is made preferably with pumpkin seed oil, which has a strong characteristic nutty flavor and striking color properties. Indeed, in a bottle it appears red, but it looks green in a salad dressing or mixed with yoghurt.

Samo and Marko Kreft¡'s paper examines the remarkable two-tone (or dichromatic) color of pumpkin seed oil, by the use of a combination of imaging and CIE (International Commission on Illumination) chromaticity coordinates. The paper also explains why human vision perceives substances like pumpkin seed oil as dichromatic or polychromatic (exhibiting a variety of colors).

Two phenomena explain the perceived shift in color of pumpkin seed oil from red to green:

Firstly, the distinctive change in color shade of the oil is due to a change in oil layer thickness. As the oil layer thickens, the oil changes its appearance from bright green to bright red. The observed color is neither dependent on the angle of observation nor on the direction or type of light.

Secondly, the shift in color is due to the unique characteristics of the cells in the human retina. Our eyes have two types of photoreceptor cells: rods and cones. Rod photoreceptor cells are very sensitive and operate in dim illumination conditions. Cone photoreceptor cells function well in bright light conditions. They are also the basis of color perception in our visual image. It is the presence of multiple classes of cone cells, each with a different spectral sensitivity, that gives us the ability to discriminate colors.

Citation: Kreft S & Kreft M (2007). Physicochemical and physiological basis of dichromatic colour. Naturwissenschaften (DOI 10.1007/s00114-007-0272-9)

Source: Springer

Explore further: Toss eggs onto salads to increase Vitamin E absorption, study says

Related Stories

The rising status of superfruits and super seeds

March 13, 2015

Superfruits and super seeds fit the bill for consumers' desire for natural, minimally processed, or unprocessed foods. Although there is no universal standard definition of a super seed or superfruit, they are often described ...

Good nutrition starts with the basics

March 15, 2012

March brings another National Nutrition Month. We Americans have unlimited sources of dietary information and frequent reminders about weight, diets, nutrition and food. Look at the magazine rack at the supermarket, the large ...

Recommended for you

Ancient parrot fossil found in Siberia

October 26, 2016

(—A Russian paleontologist has discovered a parrot fossil uncovered in Siberia several years ago—the first evidence of parrots living in Asia. In his paper published in Biology Letters, Nikita Zelenkov describes ...

Ancient burials suggestive of blood feuds

October 24, 2016

There is significant variation in how different cultures over time have dealt with the dead. Yet, at a very basic level, funerals in the Sonoran Desert thousands of years ago were similar to what they are today. Bodies of ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.