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Microbes in wine production
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Microbes in Wine Production
Xueyang Liu
Aimee. Dufresne
10/31
Microbes in wine production
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Introduction
Microbes are tiny microorganisms, which are found around us, in us and they inhibit the
world with us (Bokulich et al. 2014). Despite the fact that they are found around us, they are too
small to see with our naked eyes. However, unlike the other microorganisms such as virus and
bacteria, which causes harm to our body, microbes tend to enlighten our world in cast ways.
Some of the beneficial uses of microbes include the manufacture of delicious food products to
make delicious foods where for instance Saccharomyces cerevisiae is used to fragment sugars
thus making carbon dioxide, which makes the bread to rise (Bokulich et al. 2014). Lactobacillus
and Bifidobacteria are used to ferment milk to different degrees, and the final products will be
cheese, sour cream, yogurt and the like. Another use of microbes is to grow the leguminous
plants such as peas, clover, beans, alfalfa and soybeans and the bacteria responsible for their
growth is known as Rhizobium (Bokulich et al. 2014).
Other beneficial uses of microbes to human beings include the killing of insect pests,
during the preparation of aquarium, treating the sewage waste, during the making and breaking
down the biodegradable plastics among others (Bokulich et al. 2014). However, this paper is
going to discuss how microbes are used during the process of manufacturing wine.
Wine production
Wine is produced from the grapes. However, the process of turning the grapes into wine
is greatly facilitated by the microbial activity. It is the combination and the control of safely
maintaining the microbial activity which the quality and taste of the wine produced. The whole
process starts with the harvest of grapes which should neither be too ripe or not ripe enough. This
is because good grapes also determine the quality of the final product. The harvesting can either
Microbes in wine production
be done during the day or at night depending on the weather which is there during the time of
harvesting (Ndip et al. 2001). It may also be done using the machines, or the people themselves
may be involved in harvesting. The most important thing during the harvesting period is to beat
the heat, maximize efficiency as well as capturing grapes when they are at their stable sugar
levels (Ndip et al. 2001). Therefore, it is important to do proper planning before harvesting.
The harvested grapes are then crushed using the destemmer, which is the machine that
separated grapes from the stems and then lightly crushing the grapes (Ndip et al. 2001). It is
during this step that separates white wine from red wine. That is, during the production of white
wine, the grapes are then taken to the presser, which presses the grapes to produce the juice
before the juice is fragmented. On the other hand, some grapes are taken directly to the
fragmentation area with their skin. It is these grapes that finally produces red wine after the
fragmentation. The next step is fragmentation, and this is where the microbes take effect to
produce the perfect red and white wine.
Microbial activity during the fermentation process
Wine can be fermented using the wild yeast that comes with the grapes or yeast that
contains bacterial can be added to it (Pretorius, 2000). The bacteria, which forms the wild yeast
gets entry during the harvesting of the grapes. Their population, however, is greatly determined
by how by the level of maturity of the grapes as well as the condition of the fruit. The bacterias
can also be found on the contaminated containers valves, pulps as well as the storage containers
some of which are hard to clean (Pretorius, 2000).
There are two cycles of fermentation that takes place during the process of winemaking.
The first one is known as alcoholic fermentation. This is the cycle where yeast is added to the
3
Microbes in wine production
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Must (the juice that was pressed from the grapes which contain the seeds, stems and grapes skin).
The addition of yeast to the must assist to ferment the must as the wild yeast sometimes produce
an unpredictable outcome which might leave the wine with the sweet taste that should not
commonly be the case (BEERS, 2014). The wild yeast may also produce acetic acid which
leaves the wine with vinegar-like taste and thus producing low-quality wine. However, during
alcoholic fermentation, sulfur dioxide is added to the must before yeast is added. The first strain
of yeast to be added during the alcoholic fermentation is referred to as Saccharomyces cerevisiae
var. ellipsoideus (Lonvaud‐Funel, 2001). When this strain of yeast is added to the sugar that was
found in the Must of the grapes, carbon dioxide and alcohol are produced as the final product. It
is therefore important to leave the fermenting container open to allow the escape of carbon
dioxide, which is produced. To speed up the speed of fermentation and improve the taste of
wine, the temperature should be maintained at the range of 22 to 25 degree Celsius (Lonvaud‐
Funel, 2001). This is because low temperature reduces the speed of the microbes’ bacteria while
the high temperature will tend to kill these bacteria. In this process of fermentation, oxygen is
needed.
When alcoholic fermentation is complete, malolactic fermentation (MLF) takes over
immediately. This type of fermentation is characterized by bacterium functionality known as
Oenococcus oeni, which is also known as O. oeni (Lonvaud‐Funel, 2001). The bacteria which
was added to the must convert the malic acid that is found in the Must into lactic acid. This acid
is responsible for lowering the acidity of the wine, thus softening the overall taste of the wine
(Ndip et al. 2001). It is during this process that proteins from the grapes start to be broken down
by the lactic acid bacteria and therefore allowing particles and yeast to settle and the wine to start
clear. Oxidation must be prevented from occurring at this phase of fermentation, and this process
Microbes in wine production
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is known to take a lot of time to allow the breakdown of Must proteins. The most important
aspect to look at during this phase of malolactic fermentation is the level of pH in the wine. The
pH level in the red wine must always be maintained at 3.80, and in case the pH rises above this
level, the tartaric acid should be added to lower the pH (BEERS, 2014). The final product
produced during malolactic fermentation is carbon dioxide and lactic acid.
After the completion of this phase of fermentation, preservatives are added to the wine
produced with the aim of preventing further fermentation from taking place (BEERS, 2014).
Among them is sulfur dioxide, which is an important element in winemaking. The first work of
sulfur dioxide is to act as an anti-microbial agent before the alcoholic fermentation takes place.
Its work anti-microbial agent is to kill any wild yeast that might be present in the grapes before
yeast is added. After the second phase of fermentation is completed, sulfur dioxide is again
added to prevent any further fermentation thus preventing the wine from spoiling.
Factors, which influences the growth of Lactic Acid Bacteria (LAB) in wine
It is important to know the factors that influence the growth of lactic acid bacteria in the
wine as this knowledge helps to reduce the spoilage of wine that might occur. These factors
include:
i.
Wine/Must composition – wine may be composed of things like pH, alcohol, oxygen and
carbon dioxide as well as the nutrients.
The range of wine pH should always be 3.0 to 4.0. However, for the red wine, the pH
should be 3.4 to 3.8 for better performance (Lonvaud‐Funel, 2015). A good range will
assist in the initiation and duration of MLF thus determining the species of bacteria
Microbes in wine production
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produced by wine during fermentation and the metabolic behaviors of those organisms
and as a result, producing a high-quality by-product as a result of bacterial activity.
For the LAB to survive during the fermentation process, there must be alcohol in the
wine, and its tolerance is influenced by pH and temperature of the wine (Lonvaud‐Funel,
2015).
Oxygen is needed during the alcoholic fermentation, and the successful completion of
this phase produces carbon dioxide, which is responsible in the stimulation and growth f
LAB.
LAB also functions well when there is the presence of carbohydrates, which provides
them with energy. Vitamins and Amino acids also facilitate the growth of LAB.
ii.
Vinification Practices – factors such as fruit condition, clarification, Must treatment, skin
contact time, and lees contact, fermentation condition storage, wine clarification, and
winery sanitation affects the population and the growth of LAB (Lonvaud‐Funel, 2015).
iii.
Interrelationships with Other Organisms during the whole process of wine production –
yeast helps in the growth of LAB and also the relationship and contact with the LAB with
yeast determines the span with which LAD lives (Lonvaud‐Funel, 2015).
Microbes in wine production
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References
BEERS, J. (2014). Wine-making: The art of bacteria » The Commuter. [online]
Ncccommuter.org. Available at: http://ncccommuter.org/wine-making-the-art-of-bacteria/
[Accessed 31 Oct. 2017].
Bokulich, N. A., Thorngate, J. H., Richardson, P. M., & Mills, D. A. (2014). Microbial
biogeography of wine grapes is conditioned by cultivar, vintage, and climate.
Proceedings of the National Academy of Sciences, 111(1), E139-E148. Retrieved from
http://www.pnas.org/content/111/1/E139.full
Lonvaud‐Funel, A. (2001). Biogenic amines in wines: the role of lactic acid bacteria. FEMS
Microbiology Letters, 199(1), 9-13. Retrieved from
http://onlinelibrary.wiley.com/doi/10.1111/j.1574-6968.2001.tb10643.x/full
Lonvaud‐Funel, A. (2015). Lactic Acid Bacteria and Malolactic Fermentation in Wine.
Biotechnology of Lactic Acid Bacteria: Novel Applications, 231.
Ndip, R. N., Akoachere, J. F., Dopgima, L. L., & Ndip, L. M. (2001). Characterization of yeast
strains for wine production. Applied biochemistry and biotechnology, 95(3), 209-220.
Pretorius, I. S. (2000). Tailoring wine yeast for the new millennium: novel approaches to the
ancient art of winemaking. Yeast, 16(8), 675-729.

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