When food items, particularly potatoes, develop a green hue, it indicates a specific change in their composition. This discoloration often appears on the potato’s skin or just beneath it, signaling an alteration that can prompt questions about its safety. The term “greened” specifically refers to this visible shift in color, a common occurrence with potatoes if not stored under particular conditions.
The Cause of Greening
The green color observed on potatoes is attributed to the formation of chlorophyll. Potatoes, which naturally grow underground away from light, begin to produce chlorophyll when exposed to light, whether from sunlight or artificial sources like fluorescent store lights. This process, photosynthesis, allows plants to convert light energy into carbohydrates. While chlorophyll itself is a harmless compound, its presence serves as a visual indicator of other changes occurring within the potato.
The Associated Health Concern
The presence of chlorophyll in potatoes, while not harmful itself, signals that the same light exposure has also stimulated the production of natural toxins called glycoalkaloids. These compounds, solanine and chaconine, are natural defense mechanisms for the potato plant against pests and diseases. Consuming high amounts of these glycoalkaloids can lead to adverse health effects, including gastrointestinal symptoms such as nausea, vomiting, diarrhea, and abdominal pain. In more severe cases, neurological symptoms like headaches, dizziness, and even confusion may occur. Solanine is concentrated in and near the potato’s skin, as well as in sprouts, and often imparts a bitter flavor or a burning sensation in the mouth.
Safe Handling and Prevention
For potatoes with minor greening, the affected areas can often be removed. It is advisable to deeply peel away all of the green skin and any green-tinged flesh, as the toxins are concentrated in these parts. If a potato is extensively green throughout its flesh or if it tastes bitter after cooking, it should be discarded entirely, as sufficient solanine may remain to cause illness. To prevent greening and the associated toxin buildup, potatoes should be stored in a cool, dark, and dry place with good air circulation. Storing them in a paper bag or a well-ventilated container in a pantry helps to inhibit both chlorophyll and solanine production.