Re: How do you test if a food contains calcium. AND How do you test if a food contains iron.

Hello, Drew.

Testing for these minerals can be complicated, expensive and highly 
technical.  For example high-tech labs employ methods such as atomic 
absorption spectroscopy.  Here foods are burned to ash, dissolves out the 
mineral content in an acid. All substances reflect light waves known 
as 'light energy' and their wavelengths can be observed and measured by 
these special light-sensitive machines.

Another high-tech method is called liquid-chromotography, where similarly 
minerals are first extracted by chemicals, burning and/or acids.  The 
minerals are put through columns containing a liquid or gel which 
seperate out in different fractions.  These can then be measured and 
quantified.  

More simple methods are also possible.  For example, one can easily 
obtain analysis kits for mineral determination, (minerals are also called 
salts).  

One can determine calcium or iron content by again burning the food to 
ash and adding a solution and a binder such as EDTA (ethylene diamine 
tetra acetic acid), which preferentially binds with minerals.  The amount 
of mineral can then be calculated when complexed under specific pH levels 
with certain color indicators.  For example the color change can be 
observed as it changes from blue to pink when complexed with calcium.  

Another similar method using "colorimetric" methods which utilize 
chromogens.  Again the food is broken down with heat and dissolved in 
acid.   Chemicals are used that react with minerals to produce a soluble-
colored product which can then be analyzed.  Such changes can be 
referenced to graphs.  

Yet another more simple method utilizes electrolysis, determined by using 
selective electrodes which work on electricity where one end attaches to 
the food sample and the other end connects to a pH meter on a scale which 
the technician measures and interprets.  Such a method is useful in 
determining calcium content in milk, for example.  

Hope that helps,

Peter Bosani.

Reference:  McGraw-Hill Encyclopedia  Publisher:  McGraw-Hill.