You and Your Students!
Vicki Cobb, Education World Science Editor
Discover how packaging keeps potato chips fresh.
If a person slices potatoes very thin and fries them in hot oil, they end up with potato chips. The hot oil replaces up to 80 percent of the water in the potatoes, the slice is twice as thin as it started, and the result is crisp and crunchy, not soggy. To keep potato chips fresh, commercial manufacturers had to solve two problems:
Do the first part of this activity as a demonstration. But then you can let the kids set up their own stale potato chip experiments. You might also use this activity as an introduction to the nutritional value of potato chip -- which taste great because they are high in salt and fat.
Light a candle. Blow gently on the flame. Point out to students that your breath contains oxygen, and that your gentle blowing fans the flame; it does not extinguish it. (If you blow hard, the force of the air's motion keeps the flame from getting oxygen, and it will go out.) Use scissors to cut off the corner of a bag of potato chips to make a small hole. Aim the hole at a flame and squeeze the bag gently so you flood the flame with nitrogen. (You don't want to squeeze so hard that the force blows out the flame.) The nitrogen deprives the flame of oxygen from the air, and the flame will go out. The nitrogen also puffs up the bag to keep breakage to a minimum.
Put some of the chips from the freshly opened bag in a glass bowl in the sunlight. Leave the rest of the chips in the bag and close tightly with a bag clip, twist tie, or rubber band. Taste a chip from each group every day for a week. How do the flavors compare? Rancid potato chips won't harm you, but you'll get insight into the problem facing potato chip manufacturers -- keeping their products as fresh as long as possible.
Potato chips are America's number one snack food. They also add to the nation's obesity problem! You might share with students the nutritional information on the bag. Pay attention to portion size -- twenty chips! One portion, or 20 chips, is 150 calories and provides 15% of your daily requirement for fat.
For more fun experiments with food, check out Where's the Science Here? Junk Food by Vicki Cobb (Millbrook Press, 2006).
Article By Vicki Cobb
Copyright © 2006 Education World