A report about the Cassava treatment by the iron salt.

A bag of frozen peeled cassava was bought in Pittsburgh, PA, because this is the major city close

to Morgantown, WV (one hour of driving by car).

The unfrozen piece of cassava looks like this (cut by half to demonstrate what is inside):

The experiment was started on August 2, 2016 and continues up to this time. The control piece of

cassava was placed in the open plastic box (initially till it starts smelling), after one week was kept in

closed plastic box. All the time at room temperature (from 25 oC till 32 oC in WV, somewhat close to

Africa, because during day time no air conditioner was used – outside temperature of 33 were for

several days). After two weeks the cassava piece is completely rotten:

Another sample was treated (simply put in solution of FeCl3 with concentration of 17 mM) for one hour.

Now it is completely rotten, too:

The sample, which was hold in the same solution for one day (~ 24 hours) and later was kept on the air

in the open container in the same environment, is not rotten and seems like completely fine (after 14

days it started to be dried slowly, but I taste it on day 13 and the taste is undistinquishable from freshly

unfrozen cassava). The sample was cut (second photo) in order to demonstrate that the tint from iron

staining is much less inside compare to outside.

The sample kept immersed in the tap water was demonstrating deterioration approximately after 7-8

days. Now (15 days) it has very bad smell and bubbles coming from it (most probably HCN):

One more sample was treated in FeSO4 solution of approximately 10 mM and is fine after 9 days of

keeping at room temperature on air (the signs of my teeth are visible on both ends):

Some samples were hold all the time in solutions of FeCl3 or FeSO4. Those are in very good conditions as

well (preserved from drying and decay):

Some sample of cassava have the rest of the outer shell on them (not perfect peel). Those pieces after

exposure in iron salts (any of them) are now having green-blue color. The possible explanation is the

formation of salt Fe4[Fe(CN)6]3 what is supposed to be forming when the iron salt interacts with cyanide

formed.

Conclusion.

Despite the exact nature of the iron salt work is not absolutely clear, from the theoretical consideration

and some demonstration of HCN production (bubbles, blue marks) it seems that the iron salt is

preserving the cassava in exactly the proposed mechanism – blocking the HCN signalling molecule and

accelerating the decay of peroxides and free radicals, which are damaging the lipids. For the

establishment of the real recipy of how to apply the iron salt the additional experiments are necessary

for both peeled and most importantly unpeeled cassava.