10 March 17 The Straits Times
Once dismissed as food waste doomed for the landfills, soya bean residue has now been harnessed by local researchers and turned into a raw material to create biodegradable packaging.
A team led by Professor William Chen, director of the Food Science and Technology Programme at the Nanyang Technological University, has found a new way to extract cellulose from soya bean residue, also known as okara.
The method, which was developed over a year, involves adding a compound found commonly in detergent to okara.
The compound removes the lipids and proteins present in the residue, leaving behind just cellulose which can then be used to create materials for packaging, like biodegradable cling wrap - a thin plastic film commonly used to wrap food products.
Laboratory experiments found that the proportion of cellulose in okara samples increased from 50 per cent to around 90 per cent after they were treated with the compound.
Prof Chen explained that lipids and proteins had to be removed as they would hamper the process of turning cellulose into packaging materials in the later part of the development process.
This new method could provide a more cost-effective alternative to the more common method of using alkali and enzymes to remove lipids and proteins respectively from okara.
Enzymes are more costly and have to be used under specific conditions. Prof Chen said the cost of using enzymes to treat okara can be as high as $27,000 per kilogram of okara. His detergent treatment technology costs $120 per kilogram of okara.
"Moving forward, we will try to purify the cellulose further, and reduce the concentration of the compound used to minimise the impact on the environment," said Prof Chen.
"Now the solution comprises mostly water and about 2 per cent of the compound, which we are confident can be reduced further."
Each day, 30,000kg of okara - left over from soya milk and tofu production, for example - are discarded in Singapore and researchers have been developing ways to give this waste a new lease of life.
So far, okara has been used by researchers here to create a medium to grow yeast - a project also led by Prof Chen.
Other researchers have turned okara into mock meat products.