Green beer

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The beer immediately after the main fermentation is called green beer (rarely also fresh beer ).

It is called a young beer because the beer is not yet fully flavored at this stage. Only through storage, also called secondary fermentation or maturation, does the beer become more digestible and mature in taste. During the main fermentation, the fermentable sugars released from the malt are converted into ethanol and carbon dioxide . This can be seen from the decrease in the original wort content and the increase in the alcohol content. The yeasthas a good supply of nutrients during the main fermentation and first of all ferments mainly the low molecular weight sugars, including single, double and triple sugars. Substances that have not yet been metabolized by the yeast, for example amino acids , their breakdown products and fermentation intermediates or by-products, still remain in the green beer. The yeast only uses this nutrient supply if the sugars it prefers have already fermented.

The secondary fermentation in the storage tank, which is achieved either with so-called herbs or with residual extract, creates an artificially created nutrient deficiency situation for the yeast. This means that the above-mentioned substances are also metabolized during secondary fermentation, which means that the beer matures in taste. The maturation should also ensure that the fermentation carbonic acid binds in the beer and that the yeast settles after fermentation is complete.