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Q Why do some vegetables get sweeter in the winter?

A "This is a phenomenon called cold-sweetening," says UW-Madison horticulture professor Irwin Goldman.

As plants produce sugars through photosynthesis, most are combined and stored in the plant as starches and other large polymers. But in response to cold temperatures, some plants break down some of their energy stores into "free" sugars, such as glucose and fructose, and stash them in their cells to guard against frost damage. Sugar dissolved in a cell makes it less susceptible to freezing in the same way that salting roads reduces ice.

"It's wonderful for us. Not only does it keep the plants from freezing, but they taste sweeter too," Goldman says.

Cold-sweetening occurs in many cold-tolerant vegetable plants. Local consumers may have experienced it in Wisconsin-grown winter spinach, but it also happens in beets, broccoli, carrots and even potatoes.

In fact, Goldman says, cooks may find that cold-stored potatoes turn brown when cooked, due to caramelizing of the extra sugar. This can be avoided by moving cold potatoes to warmer storage areas to recondition them and allow the sugars to convert back to starch before cooking them.

- Produced in cooperation with University Communications