Although it is extremely difficult to pinpoint the precise beginning of human awareness of the presence and role of microorganisms in foods, the available evidence indicates that this knowledge preceded the establishment of bacteriology or microbiology as a science. The era prior to the establishment of bacteriology as a science may be designated the prescientific era.
This era may be further divided into what has been called the food-gathering period and the food-producing period. The former covers the time from the human origin over 1 million years ago up to 8,000 years ago. During this period, humans were presumably carnivorous, with plant foods coming into their diet later in this period. It is also during this period that foods were first cooked
Modern Food Microbiology
at this time understood the nature of these newly found preservation techniques. It is also doubtful whether the role of foods in the transmission of disease or the danger of eating meat from infected animals was recognized. Few advances were apparently made toward understanding the nature of food poisoning and food spoilage between the time of the birth of Christ and ad 1100.
Ergot poisoning (caused by Claviceps purpurea, a fungus that grows on rye and other grains) caused many deaths during the Middle Ages. Over 40,000 deaths due to ergot poisoning were recorded in France alone in ad 943, but it was not known that the toxin of this disease was produced by a fungus.12 Meat butchers are mentioned for the first time in 1156, and by 1248 the Swiss were concerned with marketable and nonmarketable meats.
In 1276, a compulsory slaughter and inspection order was issued for public abattoirs in Augsburg. Although people were aware of quality attributes in meats by the thirteenth century, it is doubtful whether there was any knowledge of the causal relationship between meat quality and microorganisms
Perhaps the first person to suggest the role of microorganisms in spoiling foods was A. Kircher, a monk, who as early as 1658 examined decaying bodies, meat, milk, and other substances and saw what he referred to as “worms” invisible to the naked eye. Kircher’s descriptions lacked precision, however, and his observations did not receive wide acceptance. In 1765, L. Spallanzani showed that beef broth that had been boiled for an hour and sealed remained sterile and did not spoil.
Spallanzani performed this experiment to disprove the doctrine of the spontaneous generation of life. However, he did not convince the proponents of the theory because they believed that his treatment excluded oxygen, which they felt was vital to spontaneous generation.
In 1837, Schwann showed that heated infusions remained sterile in the presence of air, which he supplied by passing it through heated coils into the infusion.9 Although both of these men demonstrated the idea of the heat preservation of foods, neither took advantage of his findings with respect to an application. The same may be said of D. Papin and G. Leibniz, who hinted at the heat preservation of foods at the turn of the eighteenth century
The history of thermal canning necessitates a brief biography of Nicolas Appert (1749–1841). This Frenchman worked in his father’s wine cellar early on, and he and two brothers established a brewery in 1778. In 1784, he opened a confectioner’s store in Paris that was later transformed into a wholesale business. His discovery of a food preservation process occurred between 1789 and 1793. He established a cannery in 1802 and exported his products to other countries.
The French navy began testing his preservation method in 1802, and in 1809 a French ministry official encouraged him to promote his invention. In 1810, he published his method and was awarded the sum of 12,000 francs.7 This, of course, was the beginning of canning as it is known and practiced today.5 This event occurred some 50 years before L. Pasteur demonstrated the role of microorganisms in the spoilage of French wines, a development that gave rise to the rediscovery of bacteria.
Leeuwenhoek in the Netherlands had examined bacteria through a microscope and described them in 1683, but it is unlikely that Appert was aware of this development and Leeuwenhoek’s report was not available in French. The first person to appreciate and understand the presence and role of microorganisms in food was Pasteur.
In 1837, he showed that the souring of milk was caused by microorganisms, and in about 1860 he used heat for the first time to destroy undesirable organisms in wine and beer. This process is now known as pasteurization.