Infusion Mashing – I do not have an exact definition for this one, but here is an interpretation. “Is the process of achieving your mash temperatures by adding measured amounts of water heated to carefully calculated temperatures to the mash. More specifically single infusion mashing, is where the mash water is added all at once and the mash is held at a single steady temperature for the entire mash. “
Essentially Infusion mashing is done with malted barley in sufficient amounts to convert all the starch in the mash to sugar for the yeast to eat. There will not be any details done on decoction or step mashing on this website; I do not believe a distiller will concern themselves with either of those processes too often. Single Infusion mashing is where the milled grain and starch is added to water, and then brought within a temperature range of about 140-160 F. Once again it is important to note that this procedure is designed for malted barley being the enzyme provider, ensure that the barley has sufficient diastatic power to convert the whole mash to sugar.
The temperature of the mash will greatly affect the finished sugar content of the mash. Higher mash temperatures 154-165 F will activate the alpha-amylase of the malted barley, promoting the random cutting effect and generally producing a less fermentable mash. This means there will be more complex sugars in solution that the yeast will not be able to eat; I do not see this being a productive application for a distiller.
The lower range of temperature, about 135-147 F will allow the beta-amylase of the malted barley to be more active, enabling more maltose to be produced. This will lead to a more fermentable mash that also produces complex aromas, hopefully carrying over into the final distillate. This would be more applicable to a distiller’s needs.
As I am sure a few smart whips have noticed the midpoint between these two was left out, and it was done so for a reason. The midpoint of about 148-153 F is where some alpha-amylase will be active, and the beta-amylase is just beginning to denature (die). This range is usually considered a happy medium between the two because it can be used to convert the mash in a short period of time with decent saccharification.
With a single infusion mash, a distiller can also add supplemental grain that is unmalted, or has been pre-treated in some way already. Unmalted cereal grains (barley, wheat, rye) are able to have their starch liquefied at the low infusion temperatures, and the enzymes can convert them. Also some products like pre-gelatinized corn flakes, rolled oats, or most flaked grain products can be added to an infusion mash without any treatment. Whole cracked corn on the other hand should be boiled for 30min or so before being added to the infusion mash so that the starch is available. Once again it is good to mention that the diastatic potential of the malted barley should always be taken into account in the grain bill, especially if supplementing the mash with extra non-barley starches. 2-row, and 6-row malted barley would have the best ability to deal with supplemental starches, pale malts can usually only modify themselves, anything darker will not degrade all the starch.
This is not meant to be an absolute guide to infusion mashing, and is by no means complete. Many homebrewing or brewing books will cover this mashing style in much more explicit detail, and will be much more thorough.