What is the reason for the blackening of potatoes after peeling

The blackening of potatoes after peeling is mainly caused by the enzymatic browning reaction between polyphenol oxidase and oxygen. This phenomenon is related to factors such as the content of phenolic substances in potatoes, storage conditions, cutting methods, metal ion contact, and variety differences.

1. Enzymatic browning reaction

Potatoes are rich in polyphenolic substances and polyphenol oxidase. After the epidermis is damaged, the cell structure ruptures, allowing enzymes to come into contact with substrates and oxidize colorless phenolic substances into brown polymers with the participation of oxygen. This reaction occurs rapidly at room temperature, causing black brown spots or overall discoloration on the surface of potatoes.

2. Phenolic compound content

Different varieties of potatoes have significant differences in phenolic compound content. Dark colored varieties such as purple skinned potatoes have a relatively slow browning rate due to their high antioxidant content, such as anthocyanins; However, some white meat varieties are more prone to significant browning after peeling due to the abundance of phenolic precursors such as tyrosine.

3. Metal ion catalysis

When using iron cutting tools to cut potatoes, the residual iron ions on the blade will accelerate the oxidation reaction. Copper ions have a stronger catalytic effect, and potato slices in contact with copper containing vessels may exhibit blue black changes. Suggest using ceramic or stainless steel knives to handle potatoes.

4. Effects of Storage Conditions

Potato starch stored at low temperatures will be converted into reducing sugars, which can serve as substrates for browning reactions. The increase in solanine content in potatoes stored under long-term light exposure can also promote oxidative discoloration. Fresh potatoes should be stored in a cool and dark place, avoiding refrigeration.

5. Differences in cutting methods

Rough peeling can cause more cells to rupture and accelerate the browning process. Using sharp knives for thin cutting can reduce the area of cell damage. Soaking in clean water immediately after cutting can isolate oxygen, but soaking for more than two hours can cause nutrient loss. To delay the discoloration of potatoes after peeling, the following measures can be taken: clean the knives and cutting boards before processing to avoid metal contamination; Immediately soak the potatoes in light salt water or lemon water after peeling, and use an acidic environment to inhibit enzyme activity; Cut and prepare before cooking to reduce exposure time. If slight black spots are found on the cut surface of potatoes, the discolored part can still be safely consumed, but if it is accompanied by odor or mucus, it should be discarded. It is recommended to store in a breathable bag in a cool place during daily storage, and avoid mixing with other fruits and vegetables to ripen.