Mysterious Case of Orange Turning Purple Finally Solved

Photo credit: Linh Pham /Unsplash

Scientists have finally solved the mysterious case in Keperra, about an orange turning purple a few hours after it was cut open.

The “mysterious fruit” was bought by Neti Moffitt at a local fruit and vegetable shop. The fruit looked and smelled perfectly normal after she cut it. Her son ate half of the orange and she left the other half sitting in a bowl overnight.

What happened to the fruit the next morning surprised her—it turned partly purple. What is even more shocking was that the scraps she threw into the bin turned out to be even more purple in colour.

Ms Moffitt immediately contacted the Queensland Health to investigate the case of the mysterious orange. Representatives collected the knife that was used to cut it, and the sharpening tool for forensic testing.

What Test Results Revealed

Anthocyanins, a naturally occurring pigment, had reacted to the traces of iron found on the knife, as revealed by a series of tests conducted at the Forensic and Scientific Services (FSS) laboratory at Coopers Plains in Southern Brisbane.

It turned out that the knife that was used to cut open the orange was sharpened about a couple of nights before the incident. The series of chemical and instrumental tests conducted included UV-Visible spectrophotometry to check for traces of metals and other contaminants, chemical spot tests, and liquid chromatography high-resolution mass spectrometer.

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Blood orange
Photo credit: willywonka070 /Pixabay

Anthocyanins are naturally found in oranges and are in high concentration in the blood oranges variety. Periods of cold storage, however, may raise the level of anthocyanins and when exposed to iron can cause discolouration. Anthocyanins are natural antioxidants and are known to be safe.

The Queensland Health did acknowledge that the discolouration on Mr Moffitt’s orange was a rare, yet a natural, occurrence. Ms Moffitt was amazed upon learning how a simple act of sharpening a knife can cause such an effect on her orange.