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Wort carbohydrates

16 January 2018
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Wort carbohydrates


Carbohydrates present in the wort are essential for the quality of the finished beer

By Michael Trommer

A growth medium for yeasts, the purpose of the carbohydrates found in the wort is the production of alcohol and carbon dioxide for people. However, the yeast’s only goal is to produce energy for its survival (ATP, adenosine triphosphate).

In the beer wort, there are valuable carbohydrates in the form of hexoses: glucose and fructose. There are also disaccharides called maltose and sucrose, and trisaccharides called maltotriose.

According to Lense, a good sugar composition in the wort is formed of:

  •         7% to 9% glucose and fructose;
  •         3% sucrose;
  •         43% to 47% maltose;
  •         11% to 13% maltotriose;
  •         and the rest is formed by dextrins, which are non-fermentable sugars.

The glucose and fructose are distributed inside the yeast cell through the plasma membrane.

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The disaccharide sucrose is decomposed into fructose and glucose by the enzyme invertase, which can be found near the plasma membrane of the yeast cell.

As for the maltose and maltotriose existing in the yeast cell, they are transported into the cell by specific transporters enzymes called maltose permease and maltotriose permease. Inside the cell, the amylase enzymes hydrolyze the maltose and the maltotriose into glucose. These reactions

occur simultaneously in the yeast cell.

With the glucose decomposition in an anaerobic medium (fermentation), alcohol and carbon dioxide are formed. That is also possible through aerobic process (respiration), in which carbon dioxide and water are formed.

Brewing yeast favors aerobic metabolism, in which more energy is produced (38 ATPs), over fermentation (only produces 2 ATPs).

Yeast Process


C6H12O6 + 6O2  g  6CO2 + 6H20 + 38 ATPs


C6H12O6  g  2C2H5OH + 2CO2 + 2 ATPs

Yeast can switch between processes: it performs fermentation (anaerobic) in environments without oxygen and respiration (aerobic) with oxygen, producing water and carbon dioxide. In the reactor (fermentation tank), the yeast initially chooses the aerobic process (respiration). When the oxygen inside the tank is completely consumed, it continues to produce energy through anaerobic process (fermentation).

According to Narziss, 98% of the fermentable

sugars in brewing fermentation are submitted to anaerobic process in the yeast, and 2% to aerobic process.


A carbohydrate synthesis called glycogen, which is produced by the yeast, occurs by the action of phosphorylase and transglucosidase enzymes. Through this, the yeast builds up its emergency carbohydrate reserve (glycogen and trehalose). This process only takes place during the aerobic stage.

Technical glossary

      Aerobic / respiration                                  occurs in environments with oxygen

      Anaerobic / fermentation                      occurs in environments without oxygen

      Glucose                                                                 colorless six-carbon sugar

      Fructose                                              six-carbon sugar found in various types of fruit

      Sucrose                                                       one molecule of glucose plus fructose

      Maltose                                                                 two molecules of glucose

      Maltotriose                                                         three molecules of glucose

      Glycogen                                              sugar chain present in the cell as food reserve

      Dextrin                                                         chain with more than three glucoses

      Carbohydrate                             any organic compound formed by hydrogen and carbon

Michael Trommer

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Michael Trommer

Michael Trommer, descendente de pais alemães que vieram para colonização do norte do Paraná e posteriormente migraram para São Paulo.

Com 28 anos de experiência profissional na área de bebidas (cervejas e sucos). Contudo, sua maior atuação foi na indústria cervejeira, onde atuou na área de produção, laboratório, desenvolvimento de produtos maltados e não maltados, padronização de processos (sistema da qualidade) e implantação de manutenção preventiva e preditiva. Presta serviços para empresas de pequeno, médio e grande porte do segmento de bebidas.

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