It is fashionable among homebrewers to dismiss adjuncts as unworthy ingredients in beer. They often cite the German “Reinheitsgebot,” a purity law promulgated in 1516 that allowed only the use of water, malted barley and hops. Yet adjuncts are viewed differently around the world. Köln and Brussels are both world-famous brewing centers. Although located within 165 miles of each other, the brewing philosophies of these cities are light years apart. While German brewers were restricted for centuries by the Reinheitsgebot, Belgian brewers have long obtained fermentables from a wide variety of sources. In fact, adjuncts play a role in some of the world’s great beer styles.
Not all brewers define adjuncts in the same way. The most common definition is any source of starch that is not malted, but also worth mentioning are “adjunct” ingredients like malted wheat and rye.
The use of adjuncts has been a popular topic of discussion over the years. “The Practical Brewer,” a classic textbook published by the Master Brewers Association of the Americas, states that “adjunct use results in beers of lighter color with a less satiating, snappier taste, greater brilliancy, enhanced physical stability and superior chill-proof qualities.” In the “Handbook of Brewing,” a chapter on adjuncts written by Graham Stewart of Heriot-Watt University adds this: “Corn gives a fuller flavor than wheat, which imparts a certain dryness. Barley gives a strong, harsher flavor. Both wheat and barley adjuncts can considerably improve head retention. Rice will also give a very characteristic flavor to beer.” Adjuncts not only lend different flavors to homebrews but also improve mouthfeel, head retention and clarity.
Adjuncts can be divided into two broad groups: kettle adjuncts and mashable adjuncts. Kettle adjuncts, like honey or candi sugar, contain fermentable sugar and are added to the kettle in the boil. Mashable adjuncts contain starch. This starch needs to be converted to sugar before it can be used by brewer’s yeast. These starchy adjuncts must be mashed, which means that enzymes degrade the starch to fermentable and unfermentable sugars and dextrins.
Most adjuncts — including rice, corn and kettle sugars — contain very little protein and they are reluctant to yield the protein they do have during mashing. So they also can be considered in terms of their ability to dilute the protein in a wort made from low-protein adjuncts and malted barley. All the protein in this wort comes from the barley, so adding a source of extract that carries no protein effectively dilutes the total protein in the wort. Protein in barley can cause haze. People generally prefer beers to be crystal clear and they expect that clarity to last for months. So by diluting protein with the proper amount of adjuncts, brewers can increase clarity and stave off the onset of chill haze.
When brewing with low-protein adjuncts, brewers must take care not to dilute the malt’s soluble nitrogen too much, or a wort may be produced that lacks enough amino acids. Yeast need simple soluble amino acids in order to grow. Nutrient deficiency can result in poor yeast performance and off-flavors. Most of the precursors to stale flavors in beer are derived from malted barley, so diluting the malt with a non-malt adjunct may reduce stale flavors.