Q: Is it correct to assume that all extract from dextrin malt is in the form of dextrins and therefore not fermentable? If dextrin malt is mashed with other malt, will the enzymes in the other malt convert the dextrins to fermentable sugars? How much dextrin (when added to a typical batch size) is appropriate for a “full-bodied” beer style? What type of extract should I expect from dextrin malt?
DM: Dextrin malt is made by a complicated process that is proprietary to the manufacturer, Briess Malting Company. Basically, the malting conditions are so manipulated that the sugars and dextrins are changed into nonfermentable isomers that also cannot be attacked by the malt enzymes, alpha and beta amylase. This means that, no matter how long the dextrin malt sits in a mash tun, little or no breakdown will occur. In addition, virtually all of the carbohydrates extracted from dextrin malt are unfermentable. These characteristics make dextrin malt an almost ideal “body builder” for beers.
I say almost ideal because, in my own experiments, I found that using very high proportions of the material can impart a starchy flavor note to the beer. When kept to a reasonable level, however, any flavor change is so slight as to be virtually undetectable. I recommend amounts of up to 0.5 lb/5-gal batch. You can go higher, but this level seems to give sufficient body enhancement, even to low-gravity brews.
Dextrin malt is most useful in lager beers because lager yeasts use more of the triple sugars in wort and thus generally give a lower terminal gravity, and a lighter body, than ale yeasts working on a wort of similar starting gravity. At the Saint Louis Brewery, we use dextrin malt to improve the mouthfeel of our Pilsener. It seems to give about 30 points specific gravity/lb/gal — a few points lower than pale brewer’s malt.
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