Accelerated Batch Fermentation is an attempt to gain economic advantage through the production of more beer with the same equipment in less time. If even a few days can be shaved off of the fermentation period needed to produce beer, there can be considerable increases in a brewery’s overall capacity. There have always been many strategies for accelerating fermentations. However, care must be taken because flavor changes will occur when fermentations are accelerated by any of these methods.

Fermentation rates can be accelerated in several ways. Both the lag phase and the active fermentation phase can be shortened by increasing the yeast pitching rate. The initial fermentation temperature can be increased, as can the temperature of the active fermentation. Breweries can also speed up fermentations by blending actively fermenting beer with fresh, aerated wort (a form of kräusening; see kräusening). A higher fermentation temperature will increase the metabolic rate of yeast and the fermentation speed, but the profile of aroma compounds in the finished beer may change unfavorably. Fermentation times can be shortened by using powdery (non-flocculent) strains of yeast or by mechanically stirring the fermenting wort. The yeast can also be roused toward the end of fermentation by the injection of carbon dioxide or by using a re-circulating device.

Flavor changes may occur because of changes in yeast growth patterns with modifications in fusel alcohols, esters, and vicinal diketones (particularly diacetyl) occurring. Therefore, even though the fermented wort may have reached limit attenuation more quickly, proper maturation is still required. Some industrial brewers have sought to shorten the maturation period as well, using technologies such as the immobilized yeast reactor. See immobilized yeast reactor.

See also fermentation.