Prep Night for the Family Dinner
1Caleb Nakamura's school culinary club is cooking a vegetable dinner for families. Their volunteer chef, Rhoda Esposito, warned the club about two problems: beets bleed red juice onto everything once they are cooked, and carrots that boil too long go limp and mushy. When Caleb asked why, she said the answer is inside the vegetables' cells. Beets and carrots are roots, and their cells are still alive when they come from the store.
2Each root cell has a thin cell membrane that controls what moves in and out. Inside the membrane, the cell stores water, sugar and, in a beet, a red pigment. Around the membrane is a stiff cell wall. The wall has tiny openings that let water and dissolved substances pass through, but it is strong. When a living cell is full of water, it presses outward against its wall, a little like an inflated ball inside a box.
3For the beet test, Chef Esposito cut a raw beet into cubes of the same size and rinsed them in cold water to wash off juice from the cells the knife had cut open. She put one cube into each of four cups holding 50 mL of water at 20 °C, 40 °C, 60 °C and 80 °C. She prepared the hot cups herself and kept each cup at its temperature for 10 minutes. Then she lifted out the cubes, and the club compared the color of each cup with a chart that runs from 0 (clear) to 10 (deep red).
4For the carrot tests, the club used carrot sticks of the same size. They clamped one end of each stick at the edge of a table, hung a 50 g weight from the other end and measured how far the tip bent. The chef boiled some sticks and let them cool before testing, and the club looked at a thin slice of each stick under a microscope.
5Last, the chef set the cut-off top of a raw carrot in a dish of water on a sunny windowsill. Within a week, new green leaves were sprouting from it. A carrot top cut from a carrot boiled for 20 minutes sat beside it and grew nothing.