Sify.com

Sydney, May 3: It was the stench of the huge piles of seafood waste on the outskirts of her home town in Tamil Nadu which pushed Indian food scientist, Renuka Karuppuswamy, to consider a more useful purpose for the rotting waste.

That childhood goal has led to a new commercial viable technique for extracting a super food supplement – a powerful antioxidant which protects cells in the human body – from prawn shells.

Now a PhD student at the University of New South Wales in Sydney, Renuka’s research promises to turn millions of tonnes of seafood waste around the world into a useful commercial health supplement.

The antioxidant Renuka has extracted is called astaxanthin, which gives cooked prawns their red colour. However, almost all the astaxanthin is contained in the shells and heads which are thrown away.

Most commercial astaxanthin is currently produced naturally from algae or synthetically by a chemical process. But, the 27-year-old UNSW Food Science and Technology PhD student has developed an extraction technique for waste prawn heads and shells which is efficient enough to make commercial-scale extraction viable. Astaxanthin sells at about $200 a gram and as well as being used as a human health supplement, it is useful in salmon and egg production.

Renuka’s technique offers not only a new source of astaxanthin but an environmentally friendly use for the hundreds of thousands of tonnes of prawn waste generated by processing plants globally each year. An estimated 1.44 million tonnes of seafood waste is generated worldwide every year, most of which is dumped in landfill or oceans.

“You just had to cover your nose,” recalls Renuka of the stinking seafood waste landfill near the fish markets of Coimbatore in Tamil Nadu, which she passed regularly on the way to school.

Renuka’s PhD project centres on the use of supercritical carbon dioxide – CO2 held under the exact pressure and temperature conditions to be in a state between gas and liquid – to separate astaxanthin out from the solvents needed to extract it from the prawn waste. Renuka’s technique works at lower temperature, recovers more astaxanthin and causes less degradation to the antioxidant than other methods.

“With the techniques I have developed you get larger quantities of the antioxidant and that means extraction from prawn shells could be commercially viable,” she says.

The work has green credentials: not only are the solvents and gas employed in the process fully recycled, the used shells can also be used as water filtering agents or to create a natural food coating which replaces petrochemical-derived waxes.