Last updated February 12, 2018 at 11:21 am
Some common food plants contain potentially lethal doses of cyanide. A team led by scientists at Monash University in Melbourne has found a way to improve food safety.
It’s long been known that many types of plants that feature heavily in foods around the world contain sometimes significant amounts of the deadly poison.
Cassava, for instance, is a tuberous shrub that underpins the diet of an estimated half a billion people, mostly in South America. If the tuber is not correctly prepared, it retains potentially lethal quantities of cyanide. In 2005, a poorly prepared batch sicked 100 children, and killed 27, in the town of Mabini in the Philippines.
Many other common foods, including sorghum, apples, apricots, flaxseed and bamboo, also contain the substance in varying amounts.
Clearly, food safety could be greatly improved if plants could be either crossbred or genetically modified to remove or reduce the poison production.
How plants store cyanide
To do this, however, it is first necessary to determine how the plants store the compound – which they must, because they do not poison themselves – but to date researchers have been unable to come up with a method that allowed them to discover it.
Strategies used to determine other components of plant chemistry, such as infrared microspectroscopy or mass spectrometry-based bioimaging, are unable to detect the presence of cyanide.
Now, a team led by Ros Gleadow, from the Monash Plant Ecophysiology Group, has successfully combined green-coloured lasers with a method of measuring the interaction between matter and electromagnetic radiation known as Raman spectrospcopy to successfully pinpoint where one important species, sorghum, keeps the cyanide it produces.
The combined approach – known as Raman hyperspectroscopy – allowed the plant tissues to be imaged down to a cellular level without being damaged.
Cyanide as a defence mechanism
To make their findings, Gleadow and her colleagues used the strategy to identify the locations of a cyanide-containing sugar compound called dhurrin in wild types of sorghum. They compared these results to those obtained using a specially mutated sorghum strain that does not produce the compound.
The team found that the cyanide is stored in the outermost layers of the plant – the cortex, surrounding the stem, the epidermis on the surface of the leaves, and in the vascular system.
This is consistent with the theory that cyanide production evolved as a defence mechanism against plant-eating animals.
The imaging strength of the Raman hyperspectroscopy was not powerful enough to reveal exactly where in the cells the dhurrin was stored. The next step, the scientists say, is to find a way to gain greater resolution and see of it is sealed in a specific organelle.
The research was published in the journal Scientific Reports.