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Crab Shells and Cassava Sap Project

by Lea Diño



I’m a senior student in a science high school in the Philippines. We are required to make an investigatory project, and my group mates and I thought of making bioplastic from cassava (Manihot esculenta) sap and chitin from leftover crab shells. We gathered lots of information from different materials, mostly from the Internet. Just two weeks ago, we came across a video in YouTube and we thought that we can pattern our methodology from the one used in the video. That video was the one featured in your website.

Here is one of the procedures, as well as the materials we used in our experiment. By the way, we used crushed crab shells.


Extraction of Chitin (from Crab shells)

1.Dilute solution of sodium hydroxide (1-10%) at high temperature (85-100°C)

2.Demineralization (treating in a dilute solution of hydrochloric acid (1-10%) at room temperature)

3.Decolorizing process – obtaining white chitin (organic solvents/very dilute solution of sodium hypochlorite)

Depending on the severity of these treatments such as temperature, duration, concentration of the chemicals, concentration and size of the crushed shells, the physico-chemical characteristics of the extracted chitin will vary. For instance, the three most important characteristics of the chitin i.e., degree of polymerization, acetylation and purity, will be affected.

We tried doing it, but didn’t get any good results. We expected to also see the clear paste we saw in the video, but all we got was a yellowish, sort-of viscous liquid. After the experiment, we tried weighing things down, and came up with the following:

1.We have read what chitin is, but we’re not sure what it really looks like.

2.And since we don’t really have a clear idea on what chitin is, we weren’t able to make the bioplastic.

Now, we thought of asking help from you and the other guys featured on the site. We really want to be successful in this, because this project was chosen along with a few others to represent our school in an upcoming local science fair. Do you have anything to say about our methodology or materials that made our trial a failure?

We would really appreciate it if you would help us. If we did it right, we’ll let you know what the results are. Thank you very much! 🙂

Crab Shells

Comments (1)

  1. Green Plastics says:

    Hi Lea! Thanks for your question. Your project sounds very interesting, but also very challenging. Your idea of looking for uses of waste chitin is an excellent one. There are enormous amounts of waste chitin not being put to use, and there are already chemists working on the problem. But as you have discovered, chitin is not an easy polymer to work with.

    For one thing, Chitin, unlike starch, is not a thermoplastic. It doesn’t soften or melt when heated; it just decomposes.

    Also, Chitin (hydrophobic) and starch (hydrophilic) are incompatible polymers. They will not form blends, or even partial blends. In mixtures of the two, there will be two separate phases, with one polymer dispersed through the other.

    Finally, Chitin, again unlike starch, is very insoluble in aqueous solution, which is not surprising for a material that evolved to provide shells for crustaceans! Getting it to dissolve requires extreme conditions, perhaps best left to professional chemists.

    You may want to try purchasing commercial chitin that has already been extracted from the shells, and using that to play around with the second part of your experiment: combining it with cassava sap to make a bioplastic. If you get anything promising, you could go back to work more on phase one!

    Good luck with your experiment, and you are definitely thinking creatively and in the right direction! The questions you are asking are exactly the questions that “the professionals” in the field are also trying to answer.

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