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Your mission is to determine fat in different foods using a simple test.
Most of us have experienced a fast-food bag or pizza box becoming translucent (slightly see-through) when exposed to foods that contain fats, oils, or grease. This is because fats and oils don’t evaporate, but seep into the spaces between the paper fibers and reflect light differently than air does. We are using this property in this activity.
Materials for each group
2 inch x 2 inch squares (approximate) of a brown paper grocery bag. You'll need one square per sample.
Cotton swabs
Water
2-3 food items known to have a high fat content (such as butter, mayonnaise, cooking oils)
2-3 food items with an unknown fat content.
Nutritional labels for foods used
Mortar and pestle, if you need to crush a solid food item.
Instructions
Label each square with the name of the food item.
Swab a small amount of water onto a brown paper bag square.
Use a new swab to put a small amount of 2-3 known fatty food item onto one brown paper square.
Swab a small amount of 2-3 unknown fatty food item onto one brown paper square. (If the food is solid, crush it using a mortar and pestle and add some water.)
Let the squares sit for 3 minutes.
Hold the squares up to the light, and arrange them from most see-through to least see-through. (You could quantify this by trying to read a large font through each one, for example.) It’s okay if some of the items are “tied.”
Take a picture of the final arrangement. Make sure the name of the food item is visible on each square.
Comprehension Questions:
Comprehension Questions:
What happened to your squares? (You may be asked to submit your picture to your teacher.)
Why did we use water as one of our substances?
Which food item was the most see-through? The least?
Did this activity help you figure out if any of your unknown foods contained fat?
Look at the nutritional labels for the foods you used. How does the fat content correspond to your results?
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