An adjunct is any ingredient, besides the malted grain, that is added to beer. There are two types of adjuncts: kettle adjuncts and mashable adjuncts. Kettle adjuncts already contain fermentable sugar so they can just be added to the kettle during the boil. Mashable adjuncts contain starch, which is unusable to yeast therefore the adjuncts must be mashed so that the enzymes can convert the starch into fermentable sugars. The most common adjuncts in brewing are rice, wheat, sorghum, corn (maize), rye, potatoes, and oats.
Reasons to Use Adjuncts:
- Improves Clarity
The proteins from malted barley create a lot of haze in the beer, a big No No. Therefore you want to dilute the protein in the wort. This is accomplished by adding low protein adjuncts such as rice and corn. Rice and corn have very little protein so when heated in the wort, they do not want to give up their protein and instead try to retain the protein. Thus adding low protein adjuncts will clarify your beer by diluting the protein from malted barley.
- Enhance Flavors by Reducing Stale Flavors
Now low protein adjuncts are good to improve clarity but you must be careful not to use them in excess because they can dilute the concentration of soluble nitrogen from the malt. If this occurs then the wort will have a low concentration of soluble amino acids that yeast needs in order to grow. The yeast will not perform to its best ability so the beer can result in off flavors. In addition malted barley contains precursors that lead to stale flavors thus to prevent that you must dilute the barley malt with a non-malt adjunct.
- Affect Color
Corn, potato, and rice will yield a beer lighter in flavor and lighter in color than an all-barley malt version of itself. Rye results in a strong distinctive bite and will give an orange tinge and spicy character to beer.
- Improve Head Retention
Unmalted barley has a high concentration of beta glucan, an enzyme that is destroyed in malted barley. Beta glucans are need to improve foam stability.
- Add Smoothness and Increase Mouthfeel
Oats add smoothness and increase mouthfeel to beers, most commonly in stouts. But you do not want to go overboard with oats because they are low in starch (so the yeast will not grow), high in protein (that will lead to a hazy beer) and high in beta glucans (which in an excess will impede lautering- a process in which the mash is separated into the clear liquid wort and the residual grain)
- Increase Alcoholic Content
Malted wheat contains a high concentration of beta amylase, an enzyme that is very efficient in breaking down starch into fermentable sugars. By using malted wheat most, if not all, the starch will be broken down into fermentable sugars and thus yielding higher alcoholic content.
Visual Charts and Guides to Adjuncts
BeerSmith Grain List includes other factors such as color and must mash.
BYO- Grains and Adjuncts Chart: Have tons of info about American, Belgian, German, and British grains.