Re: How can I test the amount of Iron, Potassium etc. in something?

Hi, Risana.

There are two ways to approach this experiment to determine the effects of 
cooking on mineral/vitamin content in vegetables.  One is very 
straightforward with little expense - but it really makes this a 
non-experiment.  The other approach will involve some expense but gives 
some actual analysis to carry out as a part of your experiment.

As I explain these two options more, you will understand what I am saying 
here.

Firstly, there is an abundance of database information available which 
contains nutrient levels in various foods.  One very extensive database is 
maintained by USDA and can be found at the following site:
 http://www.nal.usda.gov/fnic/cgi-bin/nut_search.pl

This gives you a search option for finding (almost) whatever food you are 
interested in.  For instance, if you searched broccoli, it would come up 
with raw, boiled, etc.  Then you could chart the change in nutrient level 
(for iron, potassium, Vitamin C, or ?) between the raw and the cooked form.

But this becomes just research of existing data.  You may be required to do 
more in-depth "science" for this project.

Which brings me to the second approach - actual analysis.  After preparing 
your vegetable samples, you could take them to a food analysis company or 
university in your area for determination of the minerals (analysis of 
vitamins starts getting very costly but you should be able to get 
one mineral done for about $25 per sample - perhaps reduced with some 
persuasion by a budding scientist).  Minerals are commonly detected by 
either atomic absorption (AA) or inductively coupled plasma emission (ICP). 
 
If you wanted to carry out the analysis yourself, the least costly set-up 
would be to obtain some ion specific test strip papers.  These are similar 
to ph strips in that they change color when dipped in various 
concentrations of the target ion.  The strip color is then compared to a 
provided chart that tells how much of that ion is present.  To compare your 
different samples, remember to keep a constant ratio of vegetable to 
distilled water, using just enough water to ease mashing of the vegetable.
These ion specific strips can be obtained from any scientific supply 
company (such as VWR, Fisher, Cole-Parmer)and cost in the area of $60 for 
100 strips.  Or check with an analytical lab in your area to see if they 
could give you enough for your experiment.

If you do go the analytical route, you can investigate all kinds 
of additional scenarios: 
What effect does dry heat cooking (ie. microwave with no water) have on the 
target nutrient level?
What effect does moist heat cooking (ie. boiling in water) have on the 
target nutrient level?
Is there a difference in nutrient levels in different parts of the 
vegetable (ie. broccoli stem versus florets) and does cooking have more 
effect on one part than the other?
Why do some nutrients increase in the cooked vegetable?
Is there more than one reason why the level of some nutrients decreases 
with cooking?
Can you see a relationship between the amount of change in nutrient level 
and time and/or temperature of cooking?

I hope this helps you with your experiment, Risana. Good luck! 

Carol Crouse
Food Technologist
The Food Chain Ltd.