No. 154Everyday life4 minviews 13
Published by GK Library Annex
Why does salted napa cabbage go limp?
The salt isn't cooking the cabbage. The water inside the leaves is moving out toward the salty outside.
When you salt napa cabbage for kimchi-making season, the stiff leaves go limp within half a day. It isn't because the salt dissolves or cooks the cabbage. The water filling the cabbage's cells moves out toward the salty water outside, and the force that kept the leaves firm disappears.
The water that holds it up
A cabbage leaf is made of tiny cells packed tightly together, and each one is full of water. A cell packed with water pushes against its outer wall like an inflated balloon, which lets the leaf stand stiff. Lettuce left in the fridge too long goes floppy for the same reason: that water has left.
The membrane around each cell lets water pass easily but doesn't let salt through well. When one side of such a membrane is saltier, water moves from the less salty side to the saltier side, trying to even out the concentration on both sides. This is osmosis, the effect you learn about in science class.
Salt draws the water out
When salt or strong brine touches the cabbage, the outside of the cells becomes far saltier than the inside. Water inside the cells then passes through the membrane and leaves, and the plump cells shrivel like deflating balloons. The pool of liquid at the bottom of a tub of salted cabbage is largely water that came out of the cabbage itself.
Many people think salt softens cabbage the way boiling does, but salted cabbage isn't cooked; it has simply lost water. That's why the leaves bend softly yet still feel crisp when you bite them. The seasoning soaks in more easily where the water has left, and in a salty environment the microbes that spoil kimchi have a hard time multiplying.
Using it in the kitchen
When you make seasoned cucumber or fresh kimchi, briefly salting the vegetables to draw out water keeps the seasoning from getting watery. On the other hand, if you pour a salty dressing over a salad ahead of time, it wilts quickly by the same principle, so it's better to add it right before eating.
Soaking wilted lettuce or green onions in cold water for a while can make them crisp again. This time the outside water is less salty, so water moves back into the cells. If you salt cabbage too long, it loses too much water and becomes tough and salty, so rinse it once the thick stem bends without snapping.
Salt doesn't cook cabbage; it pulls the water in its cells out toward the salty outside. Once the water leaves, the leaves lose their support and go limp.
Notes and references · General food science on osmosis and salting vegetables. This is the general principle of water moving across cell membranes. The right amount of salt and salting time vary with cabbage size, season, and type of salt.
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