Why a live frog was planted in fresh milk: food technologies of the "pre-refrigerator" era
A nondescript inhabitant of rivers, lakes and swamps is given special attention in world folklore. In Russia, she was called the princess and the guardian of the house; in the East, she personified wealth and prosperity; the ancient Egyptians had infinity. So why is the frog so honored? Did people ever believe that she had some kind of magical power? It's not about magic at all. An ordinary croak brought practical benefits - it helped to preserve milk. How she did it - read on.
What was in the "pre-refrigerator" era
The refrigerator was invented at the end of the 19th century. It entered mass use after another fifty years. With the advent of this device, the headache with food storage has disappeared. And what happened before that?
Before our homes began to "burst" with household appliances, food storage was very, very troublesome. For a regular well-fed life, it was necessary to have a cellar or possess special culinary arts: be able to salt, dry, dry, smoke, pickle - in general, in every possible way to extend the period of use of all caught and collected "provisions".
Milk was one of the most perishable foods. For long-term storage, cheese and dairy products were made from it, but fresh milk was valued most of all. Why? Because there was no sugar and sweets in such abundance as now, and the milk is saturated with lactose (milk sugar). For the inhabitants of those times, it tasted like a banana cocktail for us! Therefore, we were looking for ways to preserve this most valuable and tasty product for a longer time.
How did frogs keep milk from souring?
First, about the storage method itself. To keep milk fresh as long as possible, live frogs were planted in it. The amphibian floundered in milk for some time, after which it was released, and the milk was placed in a cool place, where it was successfully stored 5–10 times longer than its natural shelf life.
This effect is not an ancient myth - it has been confirmed by an international group of researchers led by the Russian chemist A. T. Lebedev.
The fact is that frog skin secretes special peptides. These are short proteins that transmit information to cells. Of these, the neuropeptide bradykinin, antibiotic peptides brevinins and esculentin can be isolated.
So these peptides have antibacterial and antifungal properties. They protect the frog during hibernation, which takes place in a humid environment saturated with various bacteria and other pathogens. Nature has endowed the frog with this powerful protection.
In a similar way, frogs disinfected milk from bacteria that cause fermentation and souring. Once upon a time people noticed this and took this method into service.
What scientists could not explain ...
Peptides are understandable. Scientists have identified and counted them to the nearest one. But what they didn't think of was how the frogs were able to lower the temperature of the milk? All control samples were stored under the same conditions, but in the containers where the frogs were placed, the temperature of the contents dropped. They could not explain this ...