Читать книгу Essentials of Thermal Processing - Gary Tucker S., Gary S. Tucker - Страница 12

The early Greeks believed in ‘spontaneous generation’ (that living things could originate from non‐living matter). Although Aristotle discarded this notion, he still believed that animals could arise spontaneously from other unlike organisms or from soil. His influence regarding this concept of spontaneous generation was still felt as late as the seventeenth century.

The sixteenth and seventeenth centuries were a time of great scientific advancement in areas of chemistry, mathematics, and physics. This was known as the Scientific Revolution which laid the foundations for the Age of Enlightenment in the eighteenth century, a period where science became popular with the ordinary person, and an increasingly literate population was hungry for knowledge, information, and to learn. Evening Science lectures, with demonstrations, were very popular as a form of entertainment for the working class.

In addition at that time, the Industrial Revolution was taking place in Europe in the eighteenth and nineteenth centuries. Great strides were made in the areas of textiles, steam generation, and metallurgy. Steam generation was much more efficient; fossil fuels were used for the first time, instead of wood based fuel, resulting in a much more efficient source of energy. Advances in mining techniques and metal‐working, especially iron founding, resulted in many new uses for metals like iron, copper, and tin (http://www.wikipedia.org).

Towards the end of the seventeenth century, a chain of observations, experiments, and arguments began that disproved the belief that life could be generated from non‐life. Microbiology, as a science, can be said to have begun with the development of the microscope. In the mid‐seventeenth century, although not the inventor of the microscope, Antonie van Leeuwenhoek (1632–1723) (Fig. 1.1), a Dutch draper, ground his own lenses and made small microscopes that could magnify up to 500 times. He had exceptional attention to detail and was the first to provide proper descriptions of his observations, which included protozoans from the guts of animals and bacteria from teeth scrapings. His descriptions and drawings were excellent, and he conveyed his findings in a series of letters to the British Royal Society during the mid‐1670s. Although the observation of his ‘animalcules’ stimulated much interest, it remained as an oddity until the eighteenth century.

In France, the French Revolution (1789–1799) took place, largely as a result of growing dissatisfaction due to poverty and a shortage of food and increasing malnutrition. The Napoleonic Wars (1803–1815) further influenced the economy and developments in Europe.

It was in this time that Nicolas Appert was working as a confectioner. He was born on 17 November 1749 at Charlon‐sur‐Marne. His family were not wealthy, and young Nicolas acquired an education largely through personal effort. He was trained as a chef and worked and experimented with different kinds of food processes (fermenting, distilling, and preserving) for his own interest all of his life (http://www.appert‐aina.com).

Fig. 1.1 Antonie van Leeuwenhoek, painting by Jan Verkolje.

The French Army was busy with many military campaigns, and a major concern to the French Government was that they were losing more troops to diseases like scurvy and malnutrition, than to battle casualties. In 1795, they offered a prize of 12 000 Francs (a lot of money at that time) to anyone who could find a way to safely preserve food. This offer caught the attention of Nicolas Appert. He had noticed that the sugar syrups that he used for his confectionary, kept almost indefinitely when heated, and stored in stoppered glass bottles. He began experimenting with preserving other types of food, also by heating them and storing them in stoppered jars. He worked scientifically and had a keen attention to detail. He started with using champagne bottles, but soon had them modified with a wider mouth, so that he could fill them more easily.

By 1804, he felt confident enough to test some product on the French Navy. The test was a huge success. In 1806, more tests were conducted. His invention was assessed, and early in 1810, he was informed that he could claim the award of 12 000 Francs, but had to publish the exact details of his discovery, which he did (Goldblith 1971b).

Appert is known as the Father of Canning. Heat sterilization is also known as Appertization. Although his first products were in glass bottles, he soon started using metal cans at the cannery he built with the prize money he won for his invention. He had to deliver 200 copies of his processing methods (printed at his own expense) to the French Government before they would give him his award. The book was very detailed and described the canning process much as it is still today (Appert 1810). Appert described the process as follows (Featherstone 2012):

 Enclose the foods to be preserved in bottles.

 Cork the bottles carefully.

 Boiling the bottles in water for various lengths of time (depending on the foods).

 Remove the bottles and cool them.

In 1811, he has a second edition printed in French as well as English and Swedish, and in 1823 a third, and in 1831 a fourth. The later editions were translated into many other languages (Bitting 1937).

Although Appert's methods worked, no one at the time understood why. Appert thought it was due to the heating and exclusion of air. At that time, it was widely believed that air itself was the cause of spoilage (Fig. 1.2).

There were many other people working on methods of food preservation at the time: including the Englishmen, Donkin, and Saddington (who, in 1807, were awarded five guineas for their method of using heat to preserve fruits without using sugar).

Glass jars were soon largely replaced in commercial canneries with cylindrical tin or wrought‐iron canisters (later shortened to ‘cans’), following the work of Peter Durand in 1810. The cans were cheaper and quicker to make and much less fragile than glass jars. In England, the firm of Donkin and Hall manufactured large quantities of ‘canisters’, some of which were taken on expeditions to Baffin Bay in 1814 and on Arctic explorations in 1815.

The reason for lack of spoilage was unknown at the time, since it would be another 50 years before Louis Pasteur (1822–1895), a French chemist and microbiologist proved, by demonstration, that fermentation is caused by the growth of micro‐organisms, and not due to spontaneous generation or by exposure to air.

Fig. 1.2 Nicolas Appert, drawing on Commemorative Stamp issued by Monaco in 2010.