Why should peeled potatoes not to be exposed air longer then necessary?

When potatoes are peeled, the enzymes on the surface of the potato come into contact with oxygen in the air, causing rapid browning or discoloration. This process is known as oxidation. To prevent or slow down browning, it's important to minimize the exposure of peeled potatoes to the air for an extended period.

The flesh of a potato contains an enzyme called polyphenol oxidase or tyrosinase, which when exposed to oxygen rapidly turns the potatoes brown. Additionally, the surface of a cut or peeled potato contains phenolic compounds, which are colorless. When the potatoes are cut or peeled, these compounds come into contact with the enzyme that causes them to oxidize and turn brown.

By limiting the amount of time peeled potatoes are exposed to air, you can help maintain their fresh appearance, color, and nutritional value. If you don't plan to use the potatoes right away, you can take the following steps to prevent or delay browning:

- Storing in water: Placing the peeled potatoes in a bowl of cold water may help slow down the oxidation process. The water acts as a barrier, reducing oxygen exposure. Make sure the potatoes are completely submerged and refrigerated.

- Adding an acidic solution: Submerging peeled potatoes in a slightly acidic solution, such as a mixture of water and lemon juice or vinegar, can help delay browning. The acidity helps to inhibit the activity of the enzymes responsible for browning.

- Using plastic wrap: Wrapping the peeled potatoes tightly in plastic wrap or placing them in an airtight container can help reduce oxygen exposure and prevent browning. Make sure to remove any excess water from the potatoes before wrapping them.

Remember, while these methods can slow down browning, they do not completely prevent it. If you need to keep the potatoes peeled for longer periods, you could consider processing them further (e.g., cooking or blanching) to effectively stop the browning process.