Brewery Setup Blog

Fermentation effect during beer fermentation

How does wort evolve into fresh and delicious beer? What kind of material changes are performed in the wort in the fermenter? With all kinds of questions, let us come to the beer fermentation process.

Fermentation is the conversion of the glucose in the wort by yeast into ethanol and carbon dioxide gas. Before fermentation begins, the cooled wort needs to be transferred to a container with added yeast. The final fermentation is done through three processes of primary fermentation, secondary fermentation and conditioning stages. The fermentation process generates a lot of heat, and the tank is constantly cooled to maintain the proper temperature.

1. Fermentation effect from primary fermentation

Yeast growth occurs during primary fermentation, and the primary stage of fermentation begins when yeast is introduced into the cooled wort. Yeast quickly uses available oxygen to produce an important compound for culture expansion. When the oxygen disappears, the yeast switches to the anaerobic stage, and most of the wort sugar is reduced to ethanol and carbon dioxide.

Effects of primary fermentation include: consumption of dissolved oxygen, acidification/lowering of pH,

Yeast growth or culture expansion, ethanol and carbon dioxide production, production of flavor compounds such as esters, diacetyls, sulfur-containing compounds.

Primary Fermentation Temperatures: Ales: 62-75 °F (17-24 °C), Wheat and Belgian Styles: 62-85 °F (17-29 °C), Lagers: 46-58 °F (8- 14 °C).

2. Fermentation effect produced by secondary fermentation

Diacetyl reduction occurs during secondary fermentation. Secondary fermentation refers to the stage of fermentation after most of the sugar in the wort is consumed, the fermentation rate drops sharply, most of the sugar is eventually consumed, and some secondary metabolites are converted by yeast. As the alcohol content increases and sugar and nutrients are depleted, the yeast begins to flocculate and settle.

The effects of secondary fermentation include: lower rates of ethanol and carbon dioxide production,
Diacetyl conversion, reduction of some flavor compounds by yeast metabolism or carbon dioxide scrubbing
When terminal gravity is reached, yeast flocculation and settling begin.

Secondary fermentation temperature: Ale: Same as primary fermentation (higher temperature increases diacetyl reduction rate), Lager: 40-60 °F (4-15 °C). Some brewers allow the temperature of the beer to be elevated to speed up the reduction of diacetyl. This elevated temperature usually only lasts 24 to 48 hours. Wheat and Belgian beers: same as primary fermentation (higher temperature increases diacetyl reduction rate).

3. Adjustment stage

This stage is when final gravity is reached and the tank is cooled to refrigeration temperature (31-38°F, 0-3°C). The yeast then continues to flocculate and settle, conditioning the beer by reducing various undesirable flavor compounds.

The effects of the conditioning phase include removal of most of the yeast from the beer, reduction of alcohol-stimulated flavors, and reduction of sulfur compounds, diacetyl and acetaldehyde for a more stable beer flavor.

The above is the relevant content of the fermentation process in craft beer, you can browse our news blog to learn more about beer knowledge, welcome to discuss with us!

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