Yeast fermentation process

Upper layer fermentation or lower layer fermentation? The difference between the two is the type of yeast used. This is also the standard for distinguishing between the two beer camps of ale and lager.

 Upper fermentation

Using traditional brewer’s yeast, the brewed beer has a special smell such as fruit or spices. The wine is thicker and has an alcohol content of up to 12%. The optimal drinking temperature is 6-12 °C. The Anglo-Saxons called this beer the name ale, which is the ancient word for “beer” in English.

Lower fermentation

The grape juice yeast is used for low-temperature long-time fermentation, which is not easy to deteriorate, and is suitable for mass production. It has been favored by the beer industry since the 19th century. The beer brewed in this way is called lager, which is derived from German lagern (meaning). The taste of Rag is more refreshing than that of Al, the alcohol is lower, the fragrance is more refined, and the flavor of malt and hop is quite obvious.

1. Cell division
   After the yeast is added to the wort, the yeast begins to consume the surrounding oxygen and divide and multiply.
2. Fermentation
   Yeasts devour sugar to make alcohol, carbon dioxide, and other types of aroma molecules (esters, phenols, butanedione…). The surface of the wort is covered with a thick layer of yeast filled with yeast called krausen.
3. Finished ripening
   When the sugar is getting less and less, the yeast will reabsorb some molecules, such as diacetyl, to make the beer more delicate. The metabolically completed yeast will gradually die or go to sleep and settle at the bottom of the beer tank. At this point the beer is almost finished and ready to be bottled.