Hoki Mai

101 uses for a dead fish

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After a commercial catch of hoki is processed into seafood products, the skins and bones are left over. This fishy “garbage” is routinely processed into fishmeal and fertilisers, but New Zealand has now found a cutting-edge use for it, in “electrospinning”. Plant & Food Research scientists led by Nick Tucker have spun the collagen from hoki skins into super-thin nanofibres for use in filters and, potentially, fabrics, textiles, bandages and applications in medicine and surgery.

Electrospinning teases liquid polymers out of a narrow tube with an electric field, and has been in use with other materials since early last century. As the jet of liquid moves through the air, it dries, then whips out and stretches into ultra-thin nanofibres about a tenth of the jet’s original diameter and invisible to the naked eye.

The fibres become stronger as they become thinner (because the molecules are better aligned). In addition, because they have a high surface-to-volume ratio, they have a better chance of ensnaring tiny particles than standard filters, something electrospun nanofibres have done since Petryanov filters were spun from cellulose acetate in Russia 70 years ago.

Until now, the majority of these fibres have stemmed from byproducts of the petrochemical industry which are nonbiodegradable and based on a diminishing supply of oil. As a food industry byproduct, hoki collagen is a renewable resource, and plentiful in this country providing the fisheries are managed well. While some research has been done with mammalian collagen, the more soluble hoki collagen provides a better source of protein for industrial-scale spinning. The other advantage of natural polymers is that they are biochemically more sophisticated than their synthetic counterparts, giving them potential for use in catalysing organic compounds into fuel, filtering out pollutants, absorbing sound and even storing energy. Not bad for dead fish.

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