Inside food detective work in a Brisbane lab to find out what caused that packet of noodles to turn purple


This is the mysterious case of the noodles that turned bright purple inside a Queenslander’s refrigerator.

When the Brisbane resident sent the homemade bagged noodles to Queensland Health forensic and scientific services, food detectives got to work to find out why they had changed color.

They immediately suspected bacterial contamination but had to be sure.

Color transfer from red cabbage, beetroot, squid ink coloring or other natural and artificial food compounds was also a possibility.

Inside the Coopers Plains food chemistry lab, south of Brisbane, forensic detectives analyze hundreds of samples a year for potentially harmful contamination that could pose a danger to the public.

The brightly colored noodles are among the most unusual samples the lab has received, arriving via Australia Post, rather than the preferred route: via one of Queensland Health’s public health departments.

They had spent five days in the Queenslander refrigerator and over a week on a bench before being posted – post, not express.

Senior chemist Hans Yates says food sleuthing is the “fun” part of the job.(ABC News: Janelle Miles)

Noodle tests find no match with any other compound

Queensland Health senior chemist Hans Yates then spent a month, on and off, among other jobs, analyzing how the packet of noodles turned into a beautiful shade of lavender.

“Unfortunately, not everything that is pretty is harmless to your health,” Yates warned.

Food tests exclude natural and artificial food colors, including colors from squid ink.

The purple color found on the noodles did not match any food compounds previously observed by the lab.

But when the noodles’ purple hue was tested against reference samples of violacein, a natural bacterial pigment, it matched.

Using sophisticated machines, Mr. Yates found that the wavelengths of the purplish color sample and the pigment found on the noodles were the same.

Violacein is produced by several species of bacteria, including Chromobacterium violaceum, which is commonly found in soil and water in the tropics and subtropics.

It is also often reported on rice.

But exactly how bacteria contaminated the cooked noodles remains a mystery.

Food chemist Hans Yates examines the data on a computer.
Food chemist Hans Yates spent a month analyzing purple noodles for the bacteria known as violacein.(ABC News: Janelle Miles)

The Brisbane resident who sent the purple sample to the lab for analysis also included the remaining uncooked noodles from the same package.

When the raw noodles were boiled in sterile water and left in the refrigerator for a week, no purple was observed.

The raw noodles were also cultivated by the microbiology lab for contaminants, and although a range of organisms were found, none produced a purple pigment.

Mr Yates would not speculate on how the purple bacteria could have spoiled the cooked noodles.

The noodle mystery comes after a curious case of orange slices that turned purple on a Brisbane woman’s kitchen counter three years ago, which were tested by the same lab.

This was later explained as a chemical reaction between particles of iron on a newly sharpened knife used to cut fruit and the pigments naturally present in oranges, called anthocyanins.

“If in doubt, throw it out”

Mr. Yates, who enjoys cooking at home, described food detective work as the “fun” part of his job, compared to other routine scans, such as checking the accuracy of food panels. nutritional information on food products.

“I was always going to be a chef,” he said. “Then in grade 12 I did my work experience and absolutely hated it.”

But, after studying for a TAFE degree in food technology, he successfully applied for a job in the forensic and scientific services of Queensland Health and earned a bachelor’s degree in applied science to become a qualified chemist.

Mr Yates said the purple noodles case was a timely reminder to people, especially before Christmas and New Years, that when it comes to food, “If in doubt, throw it out.”

If you have concerns about suspicious food packaging, contamination, allergens, or incorrect nutritional claims, you can report them to your local public health unit. here.


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