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Fermentation is chemical changes in organic substances produced by the action of enzymes. This general definition includes virtually all chemical reactions of physiological importance, and scientists today often restrict the term to the action of specific enzymes, called ferments, produced by minute organisms such as molds, bacteria, and yeasts. Generally, fermentation results in the breakdown of complex organic substances into simpler ones through the action of catalysts (Encarta). Fermentation , originally, is the foaming that occurs during the manufacture of wine and beer, a process at least 10,000 years old. That the frothing results from the evolution of carbon dioxide gas was not recognized until the 17th century. Louis Pasteur in the 19th century used the term fermentation in a narrow sense to describe the changes brought about by yeasts and other microorganisms growing in the absence of air (anaerobically); he also recognized that ethyl alcohol and carbon dioxide are not the only products of fermentaion (Britannica). In the 1920s it was discovered that extracts of muscle catalyze, in the absence of air, the formation of lactate from glucose and that the same intermediate compounds formed in the fermentation of grain are produced by muscle. An important generalization thus emerged: that fermentation reactions are not peculiar to the action of yeast but also occur in many other instances of glucose utilization (Britannica). Glycolysis, which means dissolution of sugar, was originally defined around 1930 as the splitting of sugar into lactate. It can be further defined as that form of fermentation , characteristic of cells in general, in which the six-carbon organic acid, pyruvic acid (or its ionized form pyruvate), coupled with the transfer of chemical energy to the synthesis of adenosine triphosphate (atp). The pyruvate may then be oxidized, in the presence of oxygen, through the tricarboxylic acid cycle, or in the absence of oxygen, be reduced to lactic acid, alcohol, or other products. The sequence from glucose to pyruvate is often called the Embden-Meyerhof pathway after two German biochemists, who, in the late 1920s and 1930s, postulated and analyzed experimentally the critical steps in that series of reactions. The term fermentation now denotes the enzyme-catalyzed, energy-yielding pathway in cells by which fuel molecules such as glucose are broken down anaerobically. In most cells the enzymes occur in the soluble portion of the cytoplasm. The reactions leading to the formation of pyruvate thus are common to sugar transformation in muscle, yeasts, some bacteria, and plants. One product of the pathway is always the energy-rich compound adenosine triphosphate (atp). The other product, pyruvate, can undergo various transformations, depending on the cell type and the availability of oxygen. Industrial fermentation processes begin with suitable microorganisms and specified conditions; e.g., careful adjustment of nutrient concentration. The products are of many types: alcohol, glycerol, and carbon dioxide from yeast fermentation of various sugars; butyl alcohol, acetone, lactic acid, monosodium glutamate, and acetic acid from various bacteria; citric acid, gluconic acid, and small amounts of antibiotics, vitamin B12, and riboflavin (vitamin B2) from mold fermentation (Britannica). When making apple cider, the brewer must know many other things than the history of fermentation and the different components of it. He must know the steps to making it successfully and the special factors that come into play when making cider. Two factors require special attention when making cider at home: oxygen supply and temperature. Oxygen is spread throughout the mixture by stirring it daily and by letting air reach the fluid through a cheesecloth filter, which is used in place of a regular lid. The temperature in the fermentation room should be between 7C and 16C, and as stable as possible. Temperatures above 16C will usually lead to spoilage, while temperatures below 7C will extend the period needed for proper fermentation. It is also that the temperature remain as constant as possible. Rapid temperature fluctuations can greatly upset the fermentation process (Morison). Ever since its beginnings, from a froth to Pasteur’s explanation to the modern-day complicated processes, fermentation has always interested people. No doubt, our understanding of the anaerobic process has grown in many respects as science has continued to grow. Fermentation is such a baffling process to watch that the research on it will continue to grow and more breakthroughs on its development and how it effects our environment will be developed as we await them with much anticipation. Bibliography: Works Cited “Fermentation,” Microsoft Encarta Online Encyclopedia 2000. http://encarta.msn.com 1997-2000 Microsoft Corporation. “Fermentation,” Encyclopedia Britannica Online Edition. http://www.britannica.com/bcom/eb/article=fermentation/9 2000. Jonson, Lee W., Ph.D. Brew Chem 101 – The Basics of Homebrewing Chemistry. Storey Publishing: Pownal, Vermont. 1996. Morison, Bruce. Fermenting and Aging the Cider – Bruce Morison’s Cider Guide. http://www.bg-mor.demon.co.uk/cider/cidferm.htm Orton, Vrest. The American Cider Book. Farrar, Straus, and Grioux: New York. 1973. Pfizer, P. The Pasteur Fermentation Centennial 1857-1957. Chas. Pfizer & Co., Inc.: New York. 1958. Rose, A.H. Economic Microbiology – Fermented Foods. Volume 7. New York: 1982. Watson, Ben. Cider – Hard and Sweet. The Countrymen Press: Vermont. 1999. Word Count: 774
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