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Tapioca finds its ‘green’ value

Biodegradable plastic made from tapioca. Telegraph picture

Jorhat, March 12: In Assam, the tapioca, locally known as ximolu alu, is mostly ignored and fed to livestock. But this apparently valueless crop has more to it than meets the eye.

Experimenting on how to make use of this low-cost crop which can be widely grown in the region, scientists of the department of biochemistry and agricultural chemistry in Assam Agricultural University here have come up with a biodegradable plastic film made from the flour of the tuber.

A part of the research work of Kritideepan Sarmah, a post-graduate student of the university, the biodegradable plastic can package small amounts of dry substances if commercially manufactured on a large scale.

Explaining the process, Priyanka Das, one of the scientists involved in the research, said the tapioca starch has to be added to glycerol (a plasticizer) and then set out to dry in a thin film on a tray.

“We took 300ml solution of tapioca starch where the strength of the starch was 9gm or 3 per cent. To this was added glycerol in the proportion of 20 per cent of the starch. If more is added, it elongates the film and if less is added, the film becomes brittle. Once the solution dries, it is peeled off, cut and sealed with various ingredients inside,” Das said.

“The last decade has seen an explosion in the level of research devoted to the development of new biodegradable materials, essentially because of the desire to protect the environment as non-biodegradable films are difficult to recycle or decompose naturally. We, therefore, took up tapioca which is a very good source of starch and will easily decompose,” she said.

The tapioca starch film decomposes in about six months and much earlier if fresh substances are packaged in it. Hence it cannot be used to package things like vegetables, fruits and sugar.

“Small quantities of dry substances like tea, pepper and spices can be packaged and stored for some time. Storing large quantities resulted in elongation and tearing of the film as its tensile strength is less than plastic,” she said.

The tapioca film’s tensile strength was found to be 9.27 megapascal (Mpa) compared to polypropylene’s 1,197 MPa. Likewise, the tapioca film’s moisture content was found to be 11.9 per cent and solubility in water in 24 hours 17.22 per cent, compared to polypropylene’s 0 per cent in both the cases.

“We will further research whether the film can be improved upon by cross linking it with other agents like citric acid or made thinner by blow drying,” Das said.

She said experiments in creating biodegradable films from rice starch or maize starch had already been done but no study had been done on how much they can carry by weight or kind of material.

Two other scientists involved in this research are Robin C. Bodo and Tarun C. Sarmah.