سؤال قراءة ستيب محلول — الفكرة الرئيسية (تدريب 5374)

(1) During the French Revolutionary Wars, the French army had a problem. A big. potentially deadly problem. It was so big that on this day in 1795, they offered 12.000 francs to anyone who could successfully solve it. (2) That problem – how to store food safely – was one shared by most of the rest of humanity, which probably explains why its solution has been so popular and lasting: canning. When left out, food, as we all know, goes bad. (3) Although food could be dried, smoked, fermented or pickled before the invention of canning, none of these methods were certain to be safe and they didn’t preserve flavor. Then came Nicolas Appert, a candy maker and winner of the prize money and the title «The Father of Canning». (4) Canning works by placing food in jars or cans and heating the whole set-up to a temperature that kills bacteria and other microorganisms. As the jars/ cans cool, a vacuum seal is formed which prevents other microorganisms from getting in. (5) Here’s the thing, though: Appert could never explain why his method worked. Appert’s work was centered around the idea of removing air from food. Appert’s method started with putting food in jars, which were then corked, and sealed off with a wax seal. The jars were wrapped in canvas and then boiled. (6) After years of experimentation, Appert decided, correctly, that the two most important factors in canning were «the absolute deprivation from contact with the exterior air» and «application of the heat in the water bath».