Alcoholic fermentation is possibly the most well known of the three types, its byproducts having been enjoyed by human civilization for millennia. Acetic acid fermentation is the process that begins where alcoholic fermentation ends. The most common result of this fermentation process is vinegar. Lactic acid fermentation is probably the oldest and most important fermentation method. Together with the alcoholic volume, the wine takes on its bouquet and aroma , as well as body, smoothness and taste.
As you discovered at the beginning, the different types of fermentation depend on the kind of wine you want to make. Next, we are going to explain the types of fermentation that exist, going deeper into the characteristics and the effects achieved with each one. This is the first step which, as you have seen, turns the must into wine. This type of fermentation can occur is two ways: taking advantage of the yeasts and bacteria that the fruit naturally has or inducing the fermentation in an artificial way, by deliberately adding the living organisms.
Although the first option is a natural process, controlling the yeasts that are added to the must gives better and greater control over the results, as it makes it easier to predict the behaviour.
This first step usually lasts between 10 and 15 days and requires constant control. Although the fermentation usually stops by itself when the volume of sugars falls and the microorganisms die due to lack of food, it is safer to control it by means of the temperature, since by increasing it or reducing it we can render the yeasts inactive.
This is the second fermentation and it aims to reduce the acidity, turning the malic acid of the fruit into lactic acid. This process results in some loss of colour and an increase in volatile acidity. This process is recommended for wines that have a lot of flavour per se , because with a white wine, for example, it would result in a wine without flavour or aroma. In common usage fermentation is a type of anaerobic respiration , however a more strict definition exists which defines fermentation as respiration under anaerobic conditions with no external electron acceptor.
Fermentation does not necessarily have to be carried out in an anaerobic environment, however. For example, even in the presence of abundant oxygen, yeast cells greatly prefer fermentation to oxidative phosphorylation, as long as sugars are readily available for consumption [1]. Sugars are the common substrate of fermentation, and typical examples of fermentation products are ethanol , lactic acid , and hydrogen.
However, more exotic compounds can be produced by fermentation, such as butyric acid and acetone. Yeast famously carries out fermentation in the production of ethanol in beers, wines and other alcoholic drinks, along with the production of large quantities of carbon dioxide.
Anaerobic respiration in mammalian muscle under periods of intense exercise which has no external electron acceptor is, under the strict definition, a type of fermentation. French chemist Louis Pasteur was the first zymologist , when in he connected yeast to fermentation. Pasteur originally defined fermentation as respiration without air.
Pasteur performed careful research and concluded, "I am of the opinion that alcoholic fermentation never occurs without simultaneous organization, development and multiplication of cells If asked, in what consists the chemical act whereby the sugar is decomposed I am completely ignorant of it.
The German Eduard Buchner , winner of the Nobel Prize in chemistry, later determined that fermentation was actually caused by a yeast secretion that he termed zymase. The research efforts undertaken by the Danish Carlsberg scientists greatly accelerated the gain of knowledge about yeast and brewing.
Ethanol tolerance of yeast is variable, ranging from about 5 percent to 21 percent, depending on the yeast strain and environmental conditions. Other fermentation methods occur in bacteria. Many prokaryotes are facultatively anaerobic.
This means that they can switch between aerobic respiration and fermentation, depending on the availability of oxygen. Certain prokaryotes, like Clostridia , are obligate anaerobes. Obligate anaerobes live and grow in the absence of molecular oxygen. Oxygen is a poison to these microorganisms and kills them on exposure. It should be noted that all forms of fermentation, except lactic acid fermentation, produce gas. The production of particular types of gas is used as an indicator of the fermentation of specific carbohydrates, which plays a role in the laboratory identification of the bacteria.
Without these pathways, that step would not occur and no ATP would be harvested from the breakdown of glucose. Improve this page Learn More. Skip to main content.
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