Reserving Your Roast

One method intended to improve the flavor of darker beers is to delay the introduction of roasted grains (reserve them) until the last moments of the mashing period. The finely ground roast grains are added in the final minutes of the mashing rest. In the right situations, that technique can produce significant improvements in the finished beer. However, it’s not always desirable or suitable. This article illustrates the Dos and Don’ts of reserving your roast during mashing.

Roasted grains contribute color and flavor to beer. In addition, they are typically more acidic than base malts. It is that acidity that some brewers fail to understand when considering the roast reserving technique.

Mash pH is important for creating good conditions for mash enzyme action. While there are several enzymes at work in the mash and all have differing optimum pH conditions, creating a mash with a room-temperature pH of between 5.3 and 5.5 tends to provide a good compromise for all. Including or reserving roast grain from your mash should consider what the effect of that roast grain addition will be on the mash pH.

When brewing with low alkalinity water such as RO or distilled water, including roast grains in the main mash can drive the mash pH well below 5.3. Therefore, it may be useful to reserve the roast grains from the main mash to keep the mash pH in the more desirable 5.3 to 5.5 range. That enables the enzymes to do their work converting the base malt starches and sugars. Conversely, when brewing with high alkalinity water, the mash pH is very likely to be well above 5.5 when the mash is primarily base malt. An excessively high mash pH can extract harsh tasting tannins and silicates from the base malts which decreases beer quality. Including the roast grain in a mash made with high alkalinity water helps drive the mash pH lower which is hopefully closer to the optimum range.

While reserving the roast grain can help create more ideal pH conditions during the main mash when brewing with low alkalinity water, the final wort pH in the kettle is likely to end up lower than the 5.3 to 5.5 range. That can produce a more acidic or tart tasting beer. That can be fine in an Irish Dry Stout, but it may not be ideal in other styles.

Most dark beer styles with significant roast content (most porters and stouts) are more pleasant tasting and smoother when their kettle wort pH is a bit higher than typical pale worts. Targeting a kettle wort pH in the 5.4 to 5.6 range helps smooth the roast flavors and can also enhance their extraction from the roast grain. To boost pH, the mashing water needs to have some alkalinity. Tailoring the mashing water alkalinity to produce that slightly elevated kettle wort pH is desirable.

As mentioned, there are beers for which reserving roast from the main mash can be desirable. Dry stout is one that benefits from the acidic kettle wort pH, but there are several others. Those styles are typically those which color is wanted in the wort, but roast flavors are not. Styles such as Schwartzbier, Munich Dunkel, Bocks, and lighter beers that need a bit more color without roast flavor, are candidates. Typically, the amount of roast grain added is low and increased color is the goal, so the roast addition is small and less likely to drive the kettle wort pH too low.

Reserving your roast is a good technique for brewers that have low alkalinity brewing water. However, it shouldn’t be used blindly. Understanding the effects and results should help you create better beers.

Enjoy!