Though fermentation has been used by people to produce palatable goods since prehistoric times, no one really knew the cause of fermentation for most of human history. Early scientists, upon the invention of the microscope and the subsequent discovery of yeast, thought that the yeast somehow contributed to fermentation by virtue of its spherical shape rather than any digestive processes. It was believed that the fermentation of foods and fruit juices was the result of molecular vibrations induced by the death of the food's cells.
This misunderstanding arose from the fact that a yeast cell, when viewed with a microscope, doesn't look alive like many protozoa do. Yeast appears to be a simple orb, with no real method of locomotion or consumption. It was not until later that the connection between yeast and fermentation was discovered. Yeast's role in fermentation could not be fully understood until scientists began realizing the biological nature of yeast. It took many years and much controversy for the top chemists of the nineteenth century to admit that yeast is a living thing. It was the result of microscopic experiments performed independently by multiple scientists in the 1830s to prove that yeast is actually a microscopic creature that reproduces by budding.
Usually what occurs when yeast are exposed to oxygen during fermentation is that they continue the anaerobic fermentation somewhat but also perform a small amount of aerobic respiration. The byproducts of this aerobic respiration are usually not as palatable to people, with acetic acid, or vinegar, numbering among those byproducts. Another inhibitor to the fermentation process other than oxygen is too much alcohol in the substance that is being fermented. If the yeast are allowed to produce so much alcohol that the substance being fermented has greater than 16-18% alcohol by volume, the fermentation runs the risk of becoming stuck.
Stuck fermentation is an unintentional halting in the fermentation of a substance. Basically, the yeast reaches a point, due to stress factors, that it ceases metabolizing and falls out of the substance. This can be a catastrophic occurrence for the producer because once a fermentation becomes stuck, it is incredibly difficult to start it again because the yeast dies.
An unusual method used to flavor beers is used by Mountain Brewing Company, a beer-making outfit in Arizona. They use a wort that includes roasted chili peppers, which have a distinctive taste that remains unchanged throughout the fermentation process. Some American malt liquors actually use dextrose as a cheap adjunct, coupled with specific enzymes, to cut the costs associated with fermentation and brewing.
Users Reading this article are also interested in: