Cornflakes and magnets - A Deeper Explanation

(Before you read: There are a ton of 2-3 minute youtube videos showing cornflakes attracted to magnets, with a short explanation. However, this article goes deeper - exploring the fortification processes, types of iron compounds added to food,and many other explanations trying to answer the question - why are cornflakes attracted to magnets?)

I was watching a youtube video about magnetism in our daily lives, when I saw someone attracting a cornflake with a magnet!

If you float a single cornflake on water in a small bowl, and get a moderately strong neodymium magnet next to it, the cornflake starts to drift towards it! Apparently the iron content in the cornflakes(which you see on the back of the box) gets attracted to the magnet, and this pulls the whole cornflake towards it.

Looking at the video, it seemed incredible that there were enough iron particles in the cornflakes, that it could be attracted by the magnet.

What was the source of this iron? Was it the iron present as minerals(which is given in the back of the box)? I always thought mineral iron is present in complex compound form, and not as plain iron particles(Iron compounds are generally not magnetic, and even if they are, they definitely wont be stronger than elemental iron and cornflake will not move as much). If that was so, anyone with an iron deficiency could just gobble up ground up iron, right?

So the first thing I did to satisfy my curiosity was try it out myself. I took a cornflake, floated it on water, and got a neodymium magnet near it, and sure enough, the cornflake started to drift towards the magnet.

So now that I knew the youtube video I was watching was for real, it was time to find out why exactly it happens. If the cornflake can be attracted to the magnet, it would have significant amounts of iron in it. Is it possible to extract this iron from the cornflakes?

When I searched this up on google, almost all the articles that came gave the same information.

Get the Iron out of Your Breakfast Cereal, Scientific American

How to extract iron from cereal, Sciencefocus.com

Firstly, most of them showed an experiment where you can literally extract iron particles out of the cornflakes, which was very surprising to me. The instructions were simple: take a bowl of cornflakes, crush them into very fine particles, put it in a ziplock bag, fill the bag with water until it reaches the height of the cornflakes, and let it sit for 30 minutes.

At this point, it would look like a gooey slimy substance. Add a little more water to make the cornflakes so that it can move freely. Now, get your strong neodymium magnets, and move it around the bag until you can see teeny tiny black dots following it. I tried the experiment, and sure enough, this worked too! I had successfully extracted pure iron particles from a bowl of cornflakes! The explanations given by these articles, however, were very simple and did not answer my questions, so I had to dig deeper.

Notice the small iron particles that follow the magnet.

Although this experiment answered one of my questions(do cornflakes actually contain pure elemental iron...yes), it gathered more questions in my head - where does this iron come from?? As far as I knew, the iron added to the corn flakes was in compound form(sulphates was what I thought). Dissolving these compounds in water definitely could not break the bonds of these compounds to free the iron particles. Being a high school chemistry student, I knew this with certainty.

At this point, one of my hypotheses was that these free iron particles may have been collected during the production process because of the various interactions between the cornflakes, and iron machinery, and these iron particles have nothing to do with the fortification process, and do not add mineral value to our body. Even though most machineries are made of stainless steel, this is the closest I could come to an answer as to why there are free iron particles. Keep in mind that even then, I was almost certain that fortification was NOT done with elemental iron, but with iron COMPOUNDS.

(Spoiler alert - I was wrong)

To learn more, I had to read more about the fortification process. I first started reading about fortification of iron in foods in general, and then went on to read about fortification in breakfast cereals.

So I began by looking up papers on iron fortification on general foods. I came across one very informative paper, which gave me the information I needed [1]. This short paper gave a brief explanation of the different compounds of iron(and elemental iron too) added during fortification, the advantages and disadvantages of certain compounds/elemental iron over others, which compounds are used to fortify different types of foods, and other topics as well. The paper focused on 4 main fortificants - Elemental iron, ferrous fumarate, ferrous bisglycinate, and FeNaEDTA(ethylenediaminetetraacetate).

After further research, I ignored the latter two, and focused mainly on elemental iron, ferrous fumarate, and ferrous sulphate, as most papers and articles that talked about breakfast cereals, talked about these three fortificants.

When fortifying food with iron, the three main things taken into consideration are[1]:

• Bioavailability - the amount of iron that is actually absorbed by the body and has an effect

• The compounds reactivity to the food itself - If the fortificant is very reactive, it can react with the food itself and change composition

• Compatibility with food matrix - how much of it can be loaded into unit mass of the food

Although ferrous sulphate can be easily absorbed by the body, it is very reactive to the food itself. Elemental iron, on the other hand, has a very low bioavailability, BUT this low bioavailability is made for by its high compatibility with food matrix.

Look at the three graphs[1](don't worry about 'inhibitors'. They're just other foods that tend to reduce absorbtion, but that's not the focus here). The first graph displays the amount of iron that can be absorbed by the body when different fortificants are used. The seconds graph shows HOW MUCH of it can be loaded to 1 kilogram of food.

Notice here, that even though elemental iron has a very low absorbability, lots of it can be added to a given amount of food. This explains the third graph, which shows the resulting effective absorbed iron, which is a result of the first two graphs.

So adding elemental iron IS a viable and widely used option. But wait! This brings me back to one of the questions I had - if fortification is done with elemental iron, why can't we just gobble up some iron filings/particles when we have an iron deficiency???

The elemental iron added to cornflakes and other breakfast cereals aren't just ground up iron filings. The elemental iron can be of different types - H-reduced, Atomized, CO-reduced Electrolytic, and Carbonyl[2]. We won't go into the details of these types, but in most breakfast cereals, electrolytic iron is most widely used for iron fortification(electrolytic iron is just a very pure form of iron derived from chemical electrolysis), as it is cheap and has a very low reactivity to the food matrix.

What differentiates electrolytic iron from any normal iron particle, apart from its purity, is its size[3]. Of the electrolytic iron in most american breakfast cereals, more than 90% by weight of the particles are less than 30 micrometers in diameter and 40% by weight are less than 10 micrometers[3].

So, long story short, contrary to my earlier belief, fortification CAN be done with plain elemental iron. However, this elemental iron isn’t just ground up iron particles thrown into cornflakes - they are extremely small particles of iron that have gone through thorough purification to maximize bioavailability. This explains why people with iron deficiencies cannot just gobble up fine particles of iron.

Another point to keep in mind, is that when electrolytic iron is used in fortification, to make up for its poor absorbability by the body, lots and lots of it is added(as the graph showed). This is why the amount of iron in the cornflakes is significant enough to pull the entire weight of the cornflake towards the magnet.

References:

[1] Iron Fortification of Foods: Overcoming Technical and Practical Barriers

[2] Fortificants: physical characteristics, selection and use with specific food vehicles

[3] Dry Cereals Fortified with Electrolytic Iron or Ferrous Fumarate Are Equally Effective in Breast-fed Infants