Fermentation Essay

This essay has a total of 3691 words and 15 pages.


It is impossible to set a date as to the first time fermentation was performed. It is
possible, however, to guess, and this guess is roughly 8,000 years ago. Wine has been
written about for centuries, in the Greek and Roman myths and scriptures. The Greek god of
wine, Dionysius, was in charge of the fermentation atop Mount Olympus. The people of this
time may not have known exactly what they were doing, but it was a somewhat complicated
procedure. The crushing of grapes, and the storing of their juices led to an amazing
beverage that is still used in current society. This process of fermentation was used
throughout the time of early Christianity, and other religions, for purposes within
sermons. Throughout the Renaissance, fermentation was used in the making of wine as well
as bread, not to mention new medical applications. Fermented products were brought to
America along with the new settlers. With new government, though, America was put into a
prohibition, which did not last long. Today, fermentation processes are carried out nearly
perfectly, without too large of variations among the products.

Although fermentation has been known of for at least 8,000 years, in 1865 Louis Pasteur
was the scientist who really discovered the process of fermentation. At this time, Pastuer
was the Dean and professor of chemistry at the Faculty of Sciences in Lille, France. He
was originally asked by a friend to investigate difficulties he was having manufacturing
alcohol by the fermentation of beetroot. Often, instead of alcohol, the fermentations were
resulting in lactic acid. At that time, fermentation leading to the production of wine,
beer, and vinegar was believed to be a simple and straightforward breakdown of sugar to
the desired molecules. It was believed that the chemical breakdown of sugar into alcohol
during the fermentation of wine and beer was due to the presence of inherent unstabilizing
vibrations. Yeast cells were found in the fermenting vats of wine and were known as living
organisms, yet they were only believed to be either a product of fermentation or catalytic
ingredients that provided useful ingredients for fermentation to proceed.

The brewers of wine, beer, and vinegar were having horrible times with quality control.
Yields of alcohol might suddenly fall off; wine might unexpectedly grow ropy or sour or
turn to vinegar; vinegar, when desired, might not be formed and lactic acid might appear
in its place; or the quality and taste of beer might unexpectedly change. Pasteur went
through with several experiments and immediately came up with clues to help him unravel
the fermentation mystery. The first clue that he noticed was that when alcohol was
fermented normally, the yeast cells were plump and budding. But when lactic acid would
form instead of alcohol, small rod like microbes were always mixed with the yeast cells.
The second clue uncovered during the analysis of the batches of alcohol showed that amyl
alcohol and other complex organic compounds were being formed during fermentation. This
could not be explained by the simple catalytic breakdown of sugar shown by Lavoisier. Some
additional processes must have been involved. The third clue was that some of these
compounds were able to rotate light, meaning they were asymmetric. Pasteur had previously
shown that only living organisms are able to create asymmetrical compounds. He concluded
and was able to prove that living cells, the yeast, were responsible for forming alcohol
from sugar, and that contaminating microorganisms turned the fermentations sour.

Over the next several years Pasteur identified and isolated the specific microorganisms
responsible for normal and abnormal fermentations in production of wine, beer, and
vinegar. He showed that if wine, beer, and milk were heated to moderately high
temperatures for a few minutes, microorganisms would be killed and thereby sterilize
(pasteurize), the batches and prevent their degradation. If pure cultures of microbes and
yeasts were added to sterile mashes uniform, predictable fermentations would follow.

It has taken many years to evolve the fermentation process to its current state. It is now
available in mass production, with the same products as individual projects. Fermentation
is used commercially to produce a wide variety of products that are consumed by people of
all ages. This fermentation is specifically called ethanol fermentation or ethyl alcohol
fermentation. This is carried out, in basic terms, by a reaction that converts a
disaccharide into CO2 and ethyl alcohol. In some cases both of these end products are
wanted, in some only one or the other is preferred. Ethanol, CH3CH2OH, is an alcohol, a
group of chemical compounds whose molecules contain a hydroxyl group, -OH, bonded to a
carbon atom. Lactic fermentation also exists but is carried out inside the body and is not
used for external use. Ethanol fermentation is used to make a lot more things then the
average person would think. Most people know it for its contributions to the creation of
all alcoholic drinks, such as wine, beer, hard liquors, and Champagne or sparkling wine.
While it is true that fermentation is used for these things it is also used in baking
foods, like bread, and in medicine in the form of rubbing alcohol.

Alcoholic fermentation has a commercial name, but a chemical existence. The chemistry
associated with it seems much harder than the simple fermentation process. It also reaches
humans on a more personal level when introduced to the body. The stages between and
including fermentation and digestion are important to the world as a whole … as well as
the past and the future.

Before the process of fermentation is spoken of, its most essential ingredient must be
understood. Yeast is what makes grape juice different than wine and what gives us fluffy
bread rather than dense hardtack. Yeast is a fungus that has the ability to carry out
aerobic respiration, but more importantly, has the ability to carry out anaerobic
respiration, which fermentation is the second step in. Yeast is made up of many components
that are shown on the table below.

Components % Of which %
Dry Materials (D.M.) 30.0-33.0 ------- -------
Nitrogen/D.M. 6.5-9.3 ------- -------
Proteins/D.M.(Nitrogen x 6.25) 40.6-58.0 Glutathion 0.5-1.5
Carbohydrates/D.M. 35.0-45.0 glycogentrehalose 5-108-20
Cellular lipids/D.M. 4.0-6.0 phospho-lipids 1-2
Minerals/M.S. 5.0-7.5 potassiumsodiumcalciummagnesiumphosphorus 0.8-2.00.01-0.20.02-0.150.04-0.180.8-1.3
Vitamins ------- Thiamin (B1)Riboflavin (B2)Pyridoxine (B6)Niacin (PP)

The majority of all yeasts reproduce through budding, but some have been observed to use
spores as their way to produce more yeast. Yeast cannot be held fully responsible for the
products that it helps produce. Enzymes contained within it have made the process of
fermentation more complex than previously thought. An enzyme called apozymase is essential
for the fermentation, but it cannot act alone. A coenzyme, conveniently called co-zymase,
works along with apozymase to bring about the alcoholic fermentation of sugar. The
co-enzyme is able to withstand very high temperatures and avoid being denatured, which
allows the enzyme to work efficiently in many environments. In addition to these two
components, phosphorus is needed. There are still many other steps in the production of
ethyl alcohol from sugar, in terms of enzymes, co-enzymes, and essential cycle steps that
show drastic changes in the chemical composition of the sugar.

The process of fermentation occurs after the process of glycolysis. When there is no
oxygen present after glycolysis, the pyruvate from glycolysis undergoes fermentation. The
process of alcoholic fermentation includes reactions which reduce pyruvate to alcohol
using the donated e- and H from NADH H (NADH is oxidized) thus recycling NAD for use
in glycolysis. There is no additional energy gain during these reactions and the whole
purpose of the fermentation process is to regenerate NAD . This process occurs in the cell

NADH H -------- NAD 2e- 2H
Alcoholic fermentation occurs because of the fermentation of ethanol and occurs in two
steps. The first reaction is a nonhydrolytic cleavage step in which Pyruvate (3C) is
decarboxylated to 2 x Acetaldehyde (2C) 2CO2. This is mediated by the enzyme Pyruvate
decarboxylase that also contains thiamine pyrophosphate (vitamin B1) as a coenzyme. The
second reaction is the reduction of the carbonyl acetaldehyde and results in the formation
of ethanol. In this step 2 x Acetaldehyde (2C) is reduced to 2 x Ethanol (2C) by the
enzyme Alcohol Dehydrogenase. Oxidation of NADH H provides the e- and H required for
this reaction and results in the regeneration of NAD . Acetaldehyde serves as the final
electron acceptor in ethanol. This is the equation:

2 x Pyruvate 2NADH H -------- 2 x Ethanol 2NAD 2CO2
Which can also be shown as:


Therefore for the incomplete breakdown of glucose under anaerobic conditions the equation is:
Glucose 2ADP 2P ------- 2 ethanol 2 ATP 2H2O 2CO2
The world's first encounters with fermentation were in the form of wine. Grapes were
crushed and then stored in barrels for a period of time. If the barrel were full of the
grape juice and in an oxygen-deprived environment, wine would be produced. How could this
be possible though, for yeast was not added to these early wines. To this day, yeast is,
for the most part, neglected to be added in the production of red wine. The grapes needed
for red wine are crushed as are grapes for white wine, but rather then filtering out the
skins like in white wine, red wine includes them in the fermentation process. Within the
skin lies the essential color dye needed to give the wine the color that it is known for,
but it also, more importantly, contains yeast. The yeast within the skins can be used for
the breakdown of the sugars within the juice into alcohol. The concentration of ethanol
produced by this fermentation varies, but under normal circumstances it will never exceed
14%. An amount greater than 14% will result in the killing of the enzymes that allow, like
apozymase, the sugars to be broken down

White wine on the other hand needs yeast, because its lack of skins leaves it
yeast-deprived, and therefore alcohol deprived. Rose wine is a combination of the two. The
skins of the grapes are allowed to sit in the vats for a recorded amount of time, two or
three days, and then taken out. The wine results in a rose color, but after the extraction
of the skins it needs to be replenished with fresh yeast that will allow it to ferment

Champagne is another commonly used alcoholic beverage that has its roots with the wines.
It is known for its bubbles and exploding corks. These are both results of what is called
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