Mon Dec 08, 2008 10:01 am
I know a few pro brewers who use the glucoamylase enzyme (Convertase 300) you're speaking of. Since enzymes are freed up as soon as they catalyze a reaction, there isn't a "proper" dosing rate when it comes to brewing. A common dosing rate is 1L (single bottle) per 15-30bbls. They simply work until all pertinent reactions are catalyzed. In other words, once added, their is no way to stop them without acidic or heat-based (pasteurization) denaturing. They are typically reserved for super high gravity beers, such as those with theoretical OGs above 1.140.
Glucoamylase should not be confused with alpha amylase enzyme (which is often used in macro breweries for starch conversion in mashes).
Another common approach for homebrewers is to use galactoamylase enzyme (Beano) towards the end of fermentation in the primary. 1 crushed tablet per 5 gallons is usually adequate.
Technically, enzymes are only supposed to work in a "lock and key" fashion. Enzymes are usually very specific in which type(s) of sugars they'll break down into monosaccharides. For example, lactase breaks down lactose into galactose and glucose. Galactosidase seems to fit well enough with maltose and maltotriose to hyrdrolyse them into monosaccharides. Glucoamylase does a slightly better job of this with most wort di and trisaccharides.
Depending on the composition of the wort, either glucoamylase or galactoamylase will break down most or all of the sugars present into yeast-digestable monosaccharides. In the case of super high gravity of worts (1.140+), it's likely that dextrins and certain trisaccharides will still be present in high enough concentrations to leave a beer with some residual sweetness and mouthfeel.
- Julian Shrago
Owner/Brewmaster
Beachwood BBQ & Brewing
Downtown Long Beach