Fermentation is the process of converting carbohydrates into acid or alcohol, using yeast or bacteria. Humans have intentionally used fermentation for thousands of years to create alcoholic beverages, pickled foods, and cultured dairy products. Beer and wine are made through fermentation of grains and grapes respectively, while pickled foods are made by soaking vegetables in salt water and vinegar. Yogurt is created by adding special bacteria to milk and allowing it to ferment.
In a general sense, fermentation is the conversion of a carbohydrate such as sugar into an acid or alcohol. More specifically, it can refer to the use of yeast to turn sugar into alcohol or the use of bacteria to create lactic acid in certain foods. This process occurs naturally in many different foods, given the right conditions, and humans have used it intentionally for many thousands of years.
The earliest uses of fermentation were most likely to create alcoholic beverages such as mead, wine, and beer. These drinks may have been created as early as 7,000 BC in parts of the Middle East. The fermentation of foods such as milk and various vegetables probably occurred a few thousand years later, both in the Middle East and in China. While the general principle is the same for all of these drinks and foods, the precise methods of achieving it and the end results differ.
Beer is made by taking a grain, such as barley, wheat or rye, germinating it and drying it and reducing it to a wort. This wort is then mixed with hot water and fermentation begins. After being further processed, the liquid is transferred to a vessel, where yeast is added to the dough. This yeast “eats” the sugar in the wort and converts it into carbon dioxide and alcohol. After a few weeks of fermentation and a further conditioning period, the beer is ready to be filtered and consumed.
The wine is created using a similar method that also involves fermentation. The grapes are pressed to release the sugar-rich juices, which are then either rapidly transferred from the skins or allowed to sit for some time to absorb some of the flavour, tannins and color from the skins. Yeast is then added and the grape juice is left to ferment for a number of weeks, at which point it is moved to different containers and processed at a slower pace, and finally aged or bottled.
Pickled foods, such as cucumbers, can be made by soaking the vegetable you want to pickle in a solution of salt water with vinegar added. Over time, the bacteria create lactic acid which gives food its distinctive flavor and helps preserve it. Other foods can be pickled by simply packing them in dry salt and allowing the natural fermentation process.
Milk can also be cultured, and people have been using this process with dairy products for nearly 5,000 years. It is speculated that early dairy products, such as yogurt, were the result of a natural process that occurred when milk was grown by bacteria that inhabited the leather sacks used to store dairy products. Yogurt nowadays is obtained by adding a series of special bacteria, such as L. acidophilus and L. bulgaricus, to the milk and keeping it at the right temperature. The bacteria begin converting the sugar in the dairy into lactic acid, eventually creating what we know as yogurt.
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