The “Julia Child” of kids’ hands-on science
The problem isn’t so much the freezing of food as what happens when it’s defrosted. See for yourself. Stick a stalk of celery in your freezer. The next day defrost it. Want to eat it? Compare it to a fresh unfrozen stalk. The perky structure of fresh celery is destroyed by ice. Water has the very unusual property of expanding and taking up more space when it changes into ice than when in a liquid state. That’s why ice cubes float and frozen unopened soda cans bulge. Expanding ice crystals destroy the cell walls of plants. Quickly freezing fresh food keeps the ice crystals smaller than slower freezing, but they are still large enough to destroy the cell walls of delicate vegetables like spinach or lettuce. But if you defrost frozen spinach from the supermarket it is beyond limp. So a salad you can defrost and serve as if it were fresh has seemed like an impossible dream.
Frederico Gomez, a Swedish scientist, is working to change this. Like Birdseye he took a close look at nature, specifically at plants that stay alive in very cold climates. He discovered that they contain a sugar called trehalose (tree-HAL-ose) that works like a natural antifreeze. Could he find a way to get trehalose into spinach leaves? If so, would the trehalose protect the structure of the spinach and keep it crisp after defrosting? This picture shows the results. The leaf on the left was treated with trehalose. The one on the right was untreated. He froze and defrosted both. The treated leaf is as crisp as if it had never been frozen!
Just because there is success in a lab doesn’t mean a defrosted salad will show up on your dinner plate any time soon. But these results are enough to keep the research going.
Move over Clarence Birdseye!
Vicki Cobb is a member of iNK's Authors on Call and is available for classroom programs through Field Trip Zoom, a terrific technology that requires only a computer, wifi, and a webcam. Click here to find out more.
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