The orange slice mysteriously turned purple overnight. And now, everything has been solved.
As reported in early September 2018, a mother in Queensland (Australia) encountered a very rare phenomenon, when the orange she cut for her child suddenly turned dark purple after a few hours. What’s more strange is that except for the color change, the taste of the orange zone is also very normal, nothing special.
No one knows what happened, not even the scientific community. But science is different from ordinary people in that they will have to thoroughly understand the causes of mysterious events, so that purple orange piece is no exception. Experts from the Queensland Laboratory of Forensic and Scientific services (FFS) collected the mysterious purple orange patches, the knife used for the cut, and the sharpening iron to conduct the examination.
The orange patch changes color overnight.
And now, the mystery has been solved.
According to new results published on ABC, that strange purple color is the product of a very natural chemical reaction, between compounds found in oranges and iron molecules in knives.
“Analysis results show that the orange discoloration is caused by the reaction of anthocyanins – the pigment in oranges – with iron and other metals when the knife is freshly sharpened ” – quoted in the published report. .
“To the current knowledge of science, these pigments do not present any hazard to human health.”
Stewart Carswell, head of the FSS chemistry team, said the team had to extract the purple molecules in oranges. They performed many tests on it, including chemical color indicator experiments and spectroscopic analysis.
According to published results, inside the purple molecule of orange contains higher levels of iron molecules and some metals than normal oranges.
Neti Moffitt – the mother in the story shared that her husband sharpened the knife 1-2 nights before cutting the orange. The knife was also washed before use.
According to Carswell, it is likely that the iron and metal molecules have adhered quite firmly to the surface of the knife after being sharpened . When exposed to anthocyanin pigments in oranges, they react and turn purple.
The experts at FSS also tried to react a normal piece of orange with the iron molecule, and a similar purple color appeared.
The orange discoloration is caused by the reaction of anthocyanins – the pigment in oranges – with iron molecules.
In fact, anthocyanins are present in many dark colored foods: red, blue, and purple. For example, red cabbage, cherries, grapes, berries… However, the concentration of anthocyanins depends on pH and temperature. The lower the temperature, the more anthocyanins tend to be concentrated, and this may be why Moffit’s oranges turn purple (she previously kept the oranges in the fridge).
With current scientific knowledge, this purple pigment does not pose any health hazard. It’s just a case study that the foods around us are made up of thousands of chemical compounds, and when exposed to thousands of chemicals in nature creates interesting phenomena.