High Gravity Fermentations
It is a procedure that employs wort at higher-than-normal concentrations, usually up to 18 degrees P and even higher (Munroe, 2006). Following fermentation and maturation, the beer is diluted with cool carbonated water to a prescribed original gravity or to a prescribed alcohol concentration.
According to Munroe (2006) there are a number of advantages and disadvantages associated with high-gravity brewing. More consistent beers (uniform alcohol, original gravity, etc.) can be produced because adjustments by dilution can be made more easily at later stages in processing.
The disadvantages of high-gravity brewing include decreased beer foam stability, a variety of stress effects on yeast, and problems with beer flavor matching compared with sales-gravity brewed beers. Increased ester production was the principal reason for changes in the flavor profile. Especially higher levels of acetate esters (ethyl acetate, isoamyl acetate) affected beer aroma, creating fruity and solvent-like odors.
Reconstitution of the high gravity wort, or fermented wort with water can occur at almost any stage during the brewing process. The later the water addition occurs, the greater the increase in brewing capacity. The quality of the dilution water employed is critical and depends on the point of addition. The later in the process it occurs the greater the quality requirement.
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