MadSci Network: Chemistry

Re: How do you find the moisture in a kernal of popcorn?

Date: Tue Sep 28 18:33:14 1999
Posted By: Phyllis Stumbo, Staff, Nutrition, University of Iowa
Area of science: Chemistry
ID: 938091074.Ch

A food chemist determines the amount in moisture in a food product by 
drying a weighed sample until it looses all its water.  To do this you need 
a sensitive scale for weighing the sample (popcorn in this case) before and 
after drying it.  

For example if you take 100 grams of popcorn (that's about  cup) and place 
it on a flat pan in a heated oven, it will start to lose water.  You can 
tell the water is evaporating because the corn will lose weight.  Good 
popcorn is 10 to 13% water, so it will finally weigh only about 87 to 90 
grams.  The technique is to take the popcorn from the oven and weigh it 
every 3-4 hours, and when two successive weights are the same you have 
evaporated all the water and you can calculate the original water content.

Popcorn that loses even a little water will not pop very well.  People who 
have worked with popcorn sometimes recommend adding some water back to 
dried-out popcorn to make it pop again.  Put 2-3 cups dry popcorn kernels 
in a quart jar and add from 1-2 tablespoons of water and shake the popcorn 
to wet it evenly.  Let it set a few hours and try to pop a few kernels.  If 
it still does not pop you might add few more drops of water and wait longer 
for it to re-hydrate.  (Be careful not to pour water in hot oil as it can 
spatter and burn your skin.) 

Below are some websites where you can learn more about popcorn.  Marion 
Ohio even has a popcorn museum at

Another site dedicated to popcorn is


Phyllis J. Stumbo, PhD, RD, LD,  Clinical Research 
Center, University of Iowa, Iowa City, IA 52242   Office (319) 384-9746 FAX 
(319) 384-8325 

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