Food Microbiology. History. Ancient Fermentations

A. Ancient Fermentations. The microbiology of foods dates back in history to well before even the initial discovery of microorganisms and the eventual appreciation of their positive and negative effects on foods. The examination of foods recovered from archaeological studies has been illuminating in terms of our understanding of ancient food-handling practices. Chemical analyses and electron microscopic examination have suggested how microorganisms might have played a role in fermentation processes. In ancient times, fermentation processes were spontaneous.

The microbial flora that initially populated the food, as well as that flora that became dominant after the “fermentation” process was complete, were largely dictated by the type of food and the environmental conditions. Nevertheless, ancient humans enjoyed a number of different fermented foods, including beer, wine, and cheese.

Whether their attraction to the products of alcoholic fermentations was more for the physiological effects as compared to their organoleptic qualities is difficult to determine retrospectively. The prescribed health benefits from the consumption of beer by the ancient Egyptians may have simply been an attempt to justify the means.

The first food fermentations were clearly accidental, arising from the contamination of foodstuffs collected from the surrounding environment. Perhaps because of their initial role in religious life, alcoholic beverages appear to be the first examples of products of food microbiology. A variety of evidence traces the origins of beer fermentation to the Sumerians in 7000 BC.

Records confirm that beer was already being drunk in Mesopotamia in approximately 4000 BC. The process as it was refined for the next 4000 years appears to be a by-product of bread making. Ancient Egyptian brewesses discovered a key element of beer fermentation when they used sprouted dry grain in preparing bread, which provided the enzymes necessary for the breakdown of starch. Since the endogenous yeast flora that would be responsible for the production of ethanol do not normally break down complex carbohydrates, adjunct ingredients are needed to initiate the fermentation process. Eventually a number of events led to the discovery of the microorganisms that were responsible for the conversion of carbohydrate to ethanol. That coupled to the elucidation of the biochemical steps in the pathway formed the knowledge base for this fermentation.

The eventual success of food fermentations was dependent on making these processes reproducible and predictable. Knowledge gained by examining ancient fermentations can be productive and illuminating. A brilliant example of this retrospective examination was reported by Delwen Samuel of the University of Cambridge and Peter Bolt of Scottish Courage Breweries (Edinburgh, Scotland). By examining residues collected from the time of Tutankhamun and the historical record of the agricultural practices some 3500 years ago, a hypothetical process was formulated and implemented on a small-scale commercial basis.

Its reduction to practice and the splendid results suggest that the beer-making process used by the ancient Egyptians had indeed been duplicated. Few scientific discoveries usually carry such organoleptically pleasing results.

B. Death. A knowledge of food safety began to accumulate as humans attempted to understand their own mortality and the reasons for death. Massive food poisoning outbreaks probably occurred as ancient societies became more organized and began dining en masse.

An ignorance of safe food-handling practices coupled with a lack of refrigeration probably provided a robust environment for the growth of pathogens. The earliest documented accounts of food poisoning outbreaks were not bacterial in nature, but due to ergot alkaloids, a secondary metabolite produced by Claviceps. This fungus is known to infect grains, including rye, wheat, barley, and oats. Consumption of these compounds led to mass epidemics during the 1200s, primarily in central Europe, but the last major outbreak was recorded as recently as the 1950s.

Death being the ultimate form of illness, one of the first discoveries of food-borne microbial disease was botulism. Botulism is derived from the Latin botulus, meaning sausage. The first outbreak was recognized in 1793 but the bacterium was not isolated for almost another 100 years. It was Emperor Leo who outlawed the consumption of blood sausage, presumably after he realized that deaths in the population were associated with this sausage. Few food safety problems have been handled in so unequivocal a manner by direct edict.

C. Key Personnel. Microbiology is one of the more recent scientific disciplines to be established, and considerable skepticism once existed that acted as an impediment to the discovery of biological processes. Perhaps no individual scientist, in virtually any field of science, has had as large an impact as Louis Pasteur. Originally trained as a chemist, Pasteur showed tremendous insight and contributed to the fields of both food fermentation and food safety.

His accomplishments spanned fields as diverse as wine production and meat spoilage. As detailed previously, the first fermentations were accidental, the result of the proliferation of endogenous microorganisms present in the starting substrate. Modern fermentations required that these endogenous microorganisms be identified and cultivated separately. The development of methods for the propagation of microorganisms was aided by the discovery of solid microbial cultivation medium that included agar, one of many accomplishments by Robert Koch and his colleagues in the late 1800s.

One of the first fermented products for which the microbial flora were dissected was beer—an accomplishment of Christian Hansen, who would also make significant contributions to dairy fermentations. One of the major dairy starter culture houses bears his name in tribute to his efforts.

The preservation of food was an important milestone as it permitted the expansion of markets for a given food. Although fermentation is a form of food preservation, the fermented product does not have the same taste and texture as the starting materials. Thermal processing was the invention of Francois (Nicholas) Appert, a confectioner. In 1809, he won a prize from the French government for developing the process to preserve meat, which involved heating filled glass jars in boiling water. The true nature of the process whereby the microorganisms were killed by heat would, however, not be revealed until the work of Louis Pasteur some 50 years later.