The two steps of alcoholic fermentation

Whether it’s good natural wine, beer or bread, at the base there is a very important process that uses the chemical reactions of sugars to get new food. It is the process we call fermentation, the one which allows us to enjoy some of the most popular foods and beverages. This is our topic today and we will talk in particular about the steps of alcoholic fermentation.

What is alcoholic fermentation?

Alcoholic fermentation, also known as Ethanol fermentation, is an anaerobic metabolic process that uses the sugars contained in natural foods, be they glucose, sucrose or fructose, degrading them into other organic compounds and thus turning them finally into cellular energy. The whole process, just like any other type of fermentation, takes place in the absence of oxygen, and bacteria and yeasts are used to make it possible. The chemical operation at the base of alcoholic fermentation is well-known since ancient times: beer, for example, dates back to the Sumerian or the Egyptian times; this means that thousands of years ago, ancient peoples knew how to use Saccharomyces to trigger an alcoholic fermentation reaction.

Alcoholic fermentation is commonly used for the production of alcoholic beverages such as wine and beer, of ethanol fuel and of bread. Furthermore, it is naturally used by some fish for energy production in situations of lack of oxygen.

The steps of alcoholic fermentation

Alcoholic fermentation generally takes place in two distinct phases:

Step 1

In the first phase, the complex sugars are split thanks to the enzyme invertase and consequently, glucose and fructose are formed. The chemical formula for this phase is:

C₁₂H₂₂O₁₁ + H₂O → C₆H₁₂O₆ + C₆H₁₂O₆

Step 2

In the second phase of alcoholic fermentation, which is by definition the real fermentation itself, the so-called glycolysis occurs, which affects glucose and fructose, according to the chemical formula:

Glucosio + 2 NAD+ + 2 ADP + 2 Pi → 2 NADH + 2 piruvato + 2 ATP + 2 H2O + 2 H+

The final equation of alcoholic fermentation has been written by the French chemist-physicist Joseph Louis Gay-Lussac in the Nineteenth century and summarizes the formation of ethanol and carbon dioxide starting from glucose:

C₆H₁₂O₆ → 2 CH₃CH₂OH + 2 CO₂

Alcoholic fermentation in wine

We have seen how the two steps that alcoholic fermentation generally follows trigger the chemical processes that lead to its various uses; however, not all alcoholic fermentation processes are the same: that of wine, for example, does not involve step 1, since sugars are already naturally present inside the grape and therefore there is no need for particular procedures to trigger the reaction. The same thing happens for example for the cider, which uses the sugars present inside apples and pears.

In conclusion, two simple steps of alcoholic fermentation give us some of our favourite foods. We will deal later with the fermentation of the wine in detail, in particular, the natural one; in the meantime, relax with a good bottle from our selection: if you want to play it safe, try one of our Mixed Cases.