The Purple Orange Mystery: Scientists Know Why The Fruit Changed Colour

No one was more baffled than Queensland mum Neti Moffitt when the orange she gave her two-year-old son turned from its regular colour to purple. 

In early September, Moffitt cut up the fruit for her son but noticed the next morning it had changed colour. She even cross-checked the colour of the slices her son had eaten the previous day which had been thrown in the bin.

They had also turned purple.

READ MORE: Why Did This Orange Turn Purple?

Moffitt contacted Queensland Health and asked them to investigate the strange occurrence--and they did.

Overnight, the orange Moffitt gave her son had turned purple. Image: Neti Moffitt

Queensland Health's Forensic and Scientific Services (FSS) tested everything from the fruit, to the knife used to cut the orange and the steel used to sharpen the knife and they came up with a few answers.

"The results of analysis have confirmed the discoloration was caused by the reaction of anthocyanins, a pigment that is naturally present in oranges, and traces of iron and/or other metals from a freshly sharpened knife," the results provided to the ABC said.

So basically the purple colour was a naturally occurring chemical reaction that can occur in oranges when they are exposed to elements like iron.

The purple colour is a naturally occurring chemical reaction. Image: Neti Moffitt.

The orange underwent a number of chemical and instrumental tests to get the result. The tests looked for metals, natural and artificial colours and pigments and pesticides.

The FFS also said the purple colour doesn't have any known effects on human health -- which is great because that really was the question on everyone's lips.

Contact Siobhan at skenna@networkten.com.au