A curious case of beef turning green while being cooked in Paikgacha municipality of Khulna has set off a wave of speculation across the country, with a food safety expert cautioning against both panic and complacency until proper tests are done.
The episode unfolded last Wednesday afternoon when a group of employees at Modern Bakery in Paikgacha were cooking beef bought for a picnic. Midway through cooking, they noticed the meat had inexplicably turned green. Startled and unnerved, they carried the pot straight to the local police station.
Days later, no one has been able to say for certain what caused the change and in the absence of answers, theories have run wild on social media, from spoiled meat to chemical contamination at the bakery.
Speaking to UNB on Friday, Dr. Mst. Minara Khatun, professor at the Department of Microbiology and Hygiene at Bangladesh Agricultural University (BAU) and a specialist in food safety and public health, said the explanation was not as simple as it might seem.
"The claim that the meat was a day old is not, by itself, a sufficient explanation for it turning green," she said. "People should neither panic over a photo circulating online nor brush off such an unusual change. In matters of food safety, scientific evidence must take precedence.
If meat shows an unnatural green colour, foul smell, sliminess or any other abnormality, it should not be eaten, the sample should be sent for laboratory testing."
Dr. Khatun said that meat stored for a single day after slaughter, at the correct temperature of 0-4 degrees Celsius, would not normally develop a green tinge. It might darken slightly or turn brownish, she said, but that is different from a distinct green colour, which is not a typical sign of ageing meat.
Many have pointed to the red-coloured broth as evidence the meat could not have been unsafe. Dr. Khatun called this an interesting but misleading observation. I
f the greenish discolouration is limited to certain parts of the meat, she explained, the broth can still take on its usual red or reddish hue since its colour comes largely from blood pigments, spices, and chemical reactions during cooking, not uniformly from the meat tissue itself. "A red broth does not scientifically confirm that the meat was safe," she said.
The butcher who sold the meat has claimed that other customers who bought from the same animal faced no problems. Some online have instead pointed fingers at chemicals allegedly used at the bakery.
She said neither claim stands on solid ground. Different cuts from the same animal can be exposed to different storage conditions, temperatures, humidity, and levels of contamination meaning one portion could turn while another does not. "Other people not falling sick is not scientific proof that the meat was safe," she said.
Equally, she added, there is no specific evidence to support the chemical-exposure theory either, since most chemicals commonly used in food settings do not turn meat green upon heating.
According to Dr. Khatun, similar instances of meat turning green have been recorded in various countries before, and science offers several possible explanations.
Chemical changes in myoglobin, the pigment that gives meat its red colour, can be one cause, as can storage at improper temperatures.
Certain hydrogen sulphide-producing bacteria can lead to the formation of sulfmyoglobin, which imparts a greenish tint.
Contact with copper or other metallic compounds may also cause similar discolouration in rare cases, though this is uncommon in typical retail settings.
Growth of pigment-producing bacteria, particularly Pseudomonas species, linked to lapses in post-slaughter handling and transport, is another possible culprit.
In some instances, she noted, the effect can even come down to how light reflects off the structure of the muscle fibres, producing a green, blue, or rainbow-like sheen with no spoilage involved at all.
Dr. Khatun called for an unbroken cold chain maintained safely from slaughter all the way to the consumer's kitchen.
She stressed the need for hygienic slaughtering and processing practices, clean environments, safe water, and trained workers throughout the supply chain.
Refrigerator and freezer temperatures should be checked regularly, she said, and consumers should stay alert to any unusual change in the meat they buy.
She also recommended keeping records of where meat comes from, when the animal was slaughtered, and how it has been stored along the way.