ATSI Peoples and Removing Toxins From Food 

Australia’s first peoples ate a large variety of plants, most of which required some form of processing in order to be consumed easily and safely. Around 20-25 known species of plants that ATSI peoples consumed needed some form of complex processing. 

The complex processing required would often take a considerable amount of time and was needed in order to leach certain products and chemicals from the plant. Leaching is the process of extracting certain chemicals or products from the plant, in this case, the undesired toxins or unpalatable substances.

Cycads were a particularly useful plant for Australia’s first peoples. In certain regions they were found in abundance and they could regenerate quickly after a fire. There are many species of cycads in Australia and most are found in or around coastal areas, particularly within tropical rainforests.

Cycads generate a large amount of fruit, however, they contain cycasin which is a neurotoxin and can cause intestinal and liver disorders. It can also break down the myelin sheath of nerves and lead to signal loss through the nerves, resulting in uncontrollable movements.


Processing the Cycad

The cycad plant usually required a complex series of steps in order to process it and make it safe to consume. The first step was to cook the plant, followed by working and grinding it into a grain like powder. The most important part of the processing of the cycad is the leaching of toxins from the plant material.

Leaching is the process of dissolving the toxins in water to remove them from the plant. Cycasin has a solubility of 56.6 gL-1. Given a plentiful supply of water the leaching of toxins from cycads was a rather simple process, yet the time required could vary from a few hours to days. The plant matter would be placed in a natural fibre net or woven basket and placed in a source of water.

The dissolution of cycasin in water is an equilibrium process and would require enough water for the reaction to proceed far enough to completion as this would allow enough desirable and safe product to be yielded.

cycasin(s) ⇌ cycasin(aq)

If the water that the plant matter was placed in was still, the process would take longer. This is because as the equilibrium shifted to the right the reaction would slow down. The water would then need to be replaced. A source of slow and steady flowing water was desirable for the leaching process.