Re: What is an orange made of?

This is a great example of a simple question with a 
complex answer.  The composition of an orange can be 
looked at in two different ways.  First, you could 
look at all of the chemical compounds found.  This 
would be an extremly long list made up of hundreds 
of proteins, essential oils, sugars, and the like.  
This list would be much larger than I could list 
here.  A second method would be to break the orange 
down to an elemental level and measure the amounts 
present (which is what I will show here).

This data is based on an average Valencia orange.  
The elemental composition varies in the different 
parts of the fruit (peel, juice, and edible portion). 
Numbers following elements indicate the percent of 
the total fresh weight of the orange (for the ones I 
could find).  Essential elements for plant growth are 
marked with a *.  They are listed in descending order 
of amount present.

Water (*Hydrogen and *Oxygen) 	(87.2% of Fresh wt.)      
*Carbon                                
*Nitrogen                                
*Potassium   (0.185%)	                   
*Calcium     (0.074%)                    
*Phosphorus  (0.022%)                    
*Magnesium   (0.015%)                   
*Sulfur      (0.014%)                    
Sodium       (0.0018%)                   
Silicon               
*Iron        (0.00078%)
*Boron       
Strontium
Aluminum

(The following are all less than 0.000057%)
*Manganese
*Copper
Titanium
Nickel
Vanadium
Chromium
Zirconium
*Molybdenum
Tin 
*Zinc 
*Chlorine
Cobalt
Barium
Silver 
Bismuth

The amounts of the trace elements is dependent on the 
soil in which the plant is growing.  This data is 
from Southern California.  To put this in 
perspective, the average orange is 130 g.  This would 
mean that the cobalt content would be LESS than 7.41 
X 10-5 (0.0000741) grams.  Not very much when you 
come to think of it.

If you have any questions, e-mail me at 
ejb190@psu.edu.

Eric J. Biddinger
Graduate Student in Horticulture
Penn State University 

Sources:
Birdsall, J.J., P.H. Derse, and L.J. Teply.  1961.  
Nutrients in California lemons and oranges.  Journal 
of the American Dietetic Association.  38:555-589.  

Sinclare, W.B.  1984.  The Biochemistry and 
Physiology of the Lemon and Other Citrus Fruits.  
Division of Agriculture and Natural Resources, 
University of Calfornia.  Oakland, CA.