Why some yams turn red after being cut?

A lot of us have been in a situation where you cut open a yam, expecting its usual creamy white or yellow flesh, only to find it turning red.

Have you ever wondered what causes this change in colour? This unexpected colour change can be puzzling, but it has a simple scientific explanation.  

When a yam is sliced, its cells break open, exposing natural compounds to oxygen in the air. Some yams contain polyphenols, natural antioxidants that react with oxygen, leading to colour changes.

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This process, known as oxidation, is similar to how apples or potatoes turn brown after being cut. In some cases, the reaction produces red, purple, or even brown hues, but it does not mean the yam is bad.  

Another reason for this colour change is the presence of anthocyanins, pigments responsible for red, blue, and purple tones in many fruits and vegetables. These pigments react to air or changes in acidity, sometimes making the yam appear reddish. 

Also, certain yams contain an enzyme called polyphenol oxidase, which speeds up oxidation when the yam is cut, further deepening the colour change.  

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As we know, not all yams give this reaction after it is cut. Some varieties, particularly those grown in West Africa, have higher polyphenol and anthocyanin content, making them more likely to turn red. Others, such as certain white or yellow yams, rarely show this colour change.  

As mentioned earlier, the red tint does not affect the taste or safety of the yam. As long as there is no foul smell, slimy texture, or mould, the yam is perfectly safe to eat. In fact, cooking often reduces the red colour, as heat breaks down some of the oxidized compounds.  

For those who prefer their yams to retain their original colour, there are a few simple tricks to slow oxidation. 

Cooking them quickly, such as boiling or frying soon after cutting, can help. Soaking the cut pieces in water also reduces exposure to oxygen, while adding a little lemon juice or vinegar can slow the reaction due to their acidity.  

So, the next time you see a yam turning red, don’t be alarmed. It’s simply a natural reaction caused by oxidation, pigments, and enzymes.

While it may look unusual, it doesn’t mean the yam is spoiled. Understanding this process can make you appreciate the natural chemistry at play in your everyday food.

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