MadSci Network: Botany

Re: Why are apples different colors?

Date: Fri Oct 20 19:13:35 2006
Posted By: David Hershey, Faculty, Botany, NA
Area of science: Botany
ID: 1161232757.Bt

This seems like a very advanced project for a 5 year old. Let me suggest some
more age-appropriate apple projects before I answer the question. If desired two
or more of the projects could be combined into a single project.

1. Apple identification - buy half a dozen different apples and have the student
develop a way to identify them based on color and shape. Good candidates would
be 'Granny Smith', 'Yellow Delicious', 'Red Delicious', ' McIntosh', 'Pink Lady'
and 'Gala'.

2. Apple taste test - have the student taste test six or more types of apples
and rank them from most favorite to least favorite. Then have the student let
friends and family do the taste test. The student can then compare his/her
preferences with the other results. 

3. Where did different apples originate? - use the internet to look up the
geographic origin of popular apple cultivars (cultivated varieties). A world map
could be labeled with the locations. For example, 'Yellow Delicious' was
discovered in West Virginia about 1914, 'Granny Smith' originated in New Zealand
about 1868 and 'McIntosh' was discovered in Ontario, Canada in 1811.

4. How many seeds in different apple cultivars?  - cut open the fruit of many
different apple cultivars and count the seeds.

On the question of "Why apples are different colors?" there are three main
patterns. Green apples are green because they contain the green pigment,
chlorophyll. Yellow apples start out green but the apple stops making
chlorophyll as it matures. The chlorophyll it contains eventually degrades to
reveal yellow carotenoid pigments that were there all along but being masked by
the chlorophyll. Red apples follow the same pattern as yellow apples but start
making a red pigment called anthocyanin.

Anthocyanins are water soluble pigments that change color with pH. A popular
student science project involves extracting anthocyanins from red or purple
cabbage leaves with hot water and using the extract as a pH indicator.
Anthocyanins could also be extracted from red apple peels.

Students often extract chlorophyll and carotenoids from leaves, especially
spinach, and separate them using paper chromatography. You Chlorophyll and
carotenoid pigments could also be extract  from apple peels. However, that seems
too advanced for a 5 year old because it requires toxic organic solvents such as


Student project on apple classification

How to do an Apple Taste Test

Re: What determines the number of seeds in an apple?

Re: How do you identify pigments as they show up on paper chromatography?

Procedures for extracting anthocyanins from red/purple cabbage

Procedures for paper chromatography of pigments in spinach leaves

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