why do potatoes change color

The Deep Dive

When potatoes are exposed to light, particularly sunlight, they begin to photosynthesize. This process involves the production of chlorophyll, the same green pigment found in leaves. Chlorophyll itself isn't harmful, but its production often coincides with the development of solanine, a glycoalkaloid that can be toxic in large quantities. Solanine gives the potato a greenish hue and can impart a bitter taste. Another common color change is browning, which happens when the potato's flesh is cut or bruised. This is a form of enzymatic browning, similar to what happens to apples or bananas. Enzymes within the potato, such as polyphenol oxidase, react with oxygen in the air. This reaction converts phenolic compounds in the potato into melanins, which are brown pigments. The extent of browning depends on the potato variety, storage conditions, and how it's prepared. Some browning can be minimized by keeping cut surfaces submerged in water or by adding an acidic element like lemon juice.

Why It Matters

Understanding why potatoes change color helps us identify potentially unsafe or unpalatable parts of the vegetable. The greening indicates solanine formation, a mild toxin that can cause digestive upset. Browning, while often just an aesthetic issue, can signal oxidation and nutrient loss, and sometimes indicates spoilage. Recognizing these changes allows consumers to make informed decisions about which parts of the potato to eat, which to discard, and how to store them properly to maintain quality and safety.

Common Misconceptions

A common misconception is that any green potato is immediately poisonous and must be thrown away. While greening does signal the presence of solanine, small green patches can be safely cut away. Only extensive greening or a bitter taste indicates a significant amount of solanine that might cause illness. Another myth is that browning is always a sign of spoilage. Enzymatic browning on cut surfaces is a chemical reaction, not necessarily a sign that the potato has gone bad, though prolonged exposure to air can lead to dehydration and spoilage.

Fun Facts

• The green color in potatoes is a sign of solanine production, a natural defense compound that can be toxic in large amounts.
• Enzymatic browning in potatoes is a chemical reaction that occurs when enzymes react with oxygen, similar to how cut apples turn brown.