Читать книгу Essentials of Thermal Processing - Gary Tucker S., Gary S. Tucker - Страница 14

Nicolas Appert's first products were packed in glass. Soon after his discovery was published, Peter Durand, a British merchant patented the idea of preserving food using tin cans. The patent (No 3372) was granted on 25 August 1810 by King George III of England. After receiving the patent, Durand did not make any canned food himself, but in 1812 sold his patent to two other Englishmen, Bryan Donkin, and John Hall, for £1000. Donkin was involved with tinning of iron sheets from 1808 and was keen to expand it to the food industry. Donkin and Hall set up a commercial canning factory and by 1813 were producing their first canned goods for the British army. In 1818, Durand introduced tin cans in the United States by re‐patenting his British patent in the United States of America (http://www.wikipedia.org).

The first ‘canisters’ were made from iron plates that were dipped into molten tin to stop it from corroding. The ends were soldered closed with molten lead. The metal was thick and the cans were heavy and strong. The cans often weighed more than the food that was in them. They had to be cut open with a hammer and chisel.

Appert also started using cans. He made them himself in his cannery. They had the capacity of between 4 and 45 pounds and could be reused. He also added handles to some of them so that they could be used as cooking pots once opened. Although he preferred round cans, he made oval and rectangular ones too, at the request of his customers (Goldblith 1971a).

Improvements to the can came when steel was invented, and this allowed for a much thinner metal which had the same strength to be used. In 1888, the hermetic double seam was invented by Max Ams. This paved the way for automated can lines to be made, whereas before about 6 cans per hour were handmade, the first automated can lines could make about 60 cans per hour. Can making lines today can run as fast as of 1500 cans per minute.

Tin is an expensive metal. In the 1930s, hot dipping of tinplate was replaced by electroplating, where much less tin can be used to perform the same job. Improvements in steel making technology have resulted in even lighter weight cans. Single reduced tinplate of 0.19–0.21 mm thickness and double reduced (DR) tinplate as thin as 0.10–0.15 mm are now used to make cans all over the world.

Although improvements in can design (e.g. by beading the body walls) can compensate to some extent for the loss of strength due to the thinner metal, many of the down‐gauging improvements are possible only due to improvements in can handling.