Experts Warn Consumers Against Eating Spoilt, Dark-Stained Yam

Food safety experts and farmers have cautioned Nigerians against consuming dark-stained yams, warning that certain forms of discolouration may indicate spoilage and pose serious health risks.

The Lagos State All Farmers Association of Nigeria and a public health expert gave the warning in separate interviews with the News Agency of Nigeria in Lagos on Sunday.

They explained that while some yam tubers may darken without becoming unsafe to eat, soft black patches, foul odours and visible mould could signal decay.

The stakeholders identified several possible causes of yam discolouration and deterioration, including fertiliser use, rodent attacks, accidental injuries during weeding and possible microbial contamination.

The Lagos State AFAN Chairman, Mr Sakin Agbayewa, said the colour of yam could be influenced by the type of fertiliser used during cultivation.

He also identified fertiliser application, rodent attacks and accidental cuts to tubers during weeding as factors that could affect yam quality.

According to him, rodents sometimes attack yam tubers planted in heaps and eat portions of them without farmers noticing the damage.

Farmers might cover holes in yam heaps with soil without realising that rodents had damaged the tubers, causing the affected yams to deteriorate as they matured.

Agbayewa added that cutlasses used during weeding could accidentally injure yam tubers, leaving exposed areas vulnerable to decay.

A public health expert, Prof. Tanimola Akande, said the safety of dark-stained yam depended on the cause and extent of the discolouration.

He explained that yam could naturally darken after exposure to air and might remain safe for consumption if there were no other signs of spoilage.

Akande warned, however, that soft black patches, unpleasant smells and visible mould could indicate rotting caused by bacterial or fungal activity.

According to him, eating rotten yam could expose consumers to harmful microorganisms or toxins, potentially resulting in stomach cramps, nausea, vomiting, fever and diarrhoea.

He advised consumers to avoid eating tubers showing signs of decay and to inspect yams carefully before preparing them. Akande stressed that distinguishing natural darkening from discolouration associated with spoilage was important in reducing food safety risks.

The warning comes amid rising concerns in Lagos over the prevalence of discoloured yams, popularly called “chocolate yam”. Consumers have complained that the discolouration is only discovered after cutting the tubers open, leading to financial losses and lost appetite.

A Festac resident, Ms Divine-Favour Johnson, expressed her frustration after purchasing affected yams. “You don’t understand the pain that comes with chocolate yam. Consumers suffer financial losses and lose their appetite,” she said.

“Imagine buying yam with your own money after you have saved to buy it. You then cut the yam open and discover that it is chocolate inside, like a spoilt yam”.

Mr Samuel Arowojolu, a diesel operator in Oshodi, said he had experienced yam discolouration several times, noting that the problem appeared to be becoming more common.

“If you should go to a market where they sell yam, out of five different places you might try to purchase from, you might get two that will bring out discolouration,” he said.

The concerns have also prompted the Environmental Health Officers Association of Nigeria, Lagos State Chapter, to direct environmental health officers to intensify enforcement against alleged chemical adulteration of staple foods.