It is hot outside these days. We’d better keep our milk good and cold on days like these. But how? Well. Most of us keep it in the refrigerator.
But that hasn’t always been the case. Before refrigeration came along, in parts of rural Russia, Finland, and other areas of Northern Europe, people reportedly placed a live frog into containers of milk. The belief was that the frog helped keep the milk fresh longer.
For a long time, scientists assumed this was simply folklore. But never assume anything. They began investigating out of curiosity.
In the 1980s and later, scientists started studying certain frog species. In particular, they looked at the Russian brown frog (Rana temporaria). Guess what they found. They discovered that the brown frog’s skin produces a variety of antimicrobial substances. Frogs live in damp environments full of bacteria and fungi, so they have evolved chemical defenses to protect themselves.
One group of compounds discovered in frog skin secretions was named “temporins.” And ta-da! These peptides can inhibit the growth of various bacteria.
Researchers proposed that when a frog was placed in milk, tiny amounts of these protective chemicals could have entered the liquid and slowed bacterial growth, helping the milk remain drinkable longer than it otherwise would have.
It appears that generations of rural people stumbled onto a real biological phenomenon long before microbiologists understood why it worked. But who was the first person who said to themselves, “I’m putting my frog in the milk.”
For now, I’m sticking with the old Subzero for the milk and everything else. And the frogs can just enjoy their days hanging out at our koi pond.
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“The more I learn, the more I realize how much I don’t know.” — Albert Einstein
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“The oldest and strongest emotion of mankind is fear, and the oldest and strongest kind of fear is fear of the unknown.” — H. P. Lovecraft
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“Science is simply common sense at its best.” — Thomas H. Huxley
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“The trouble with facts is that there are so many of them.” — Samuel McChord Crothers
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