Holes in Swiss Cheese - level 2
After old stories about hungry mice, many random guesses, and a hundred years of research, we now know why Swiss cheese has holes in it. And mice are not responsible.
There are holes in cheese because of hay. Very small particles of hay get into the milk and create holes when the milk turns into cheese.
Over the last 15 years, the holes have been getting smaller, or are gone completely. This is thanks to modern milking systems –milk is much cleaner than before. The amount of hay dust added to the milk can control the number of holes.
Difficult words: random guess (when you say that something could be true, but you do not really know why), research (scientific study), hay (dried grass which is fed to animals).
You can read the original story and watch the video in the Level 3 section.
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