Brewing by Ratio
Grist ratio, the amount of each ingredient going into your mash, or even partial mash, is critical to both brewing to style and brewing beer that turns out predictable, and tasting great. Let’s start by discussing the most important key to proper malt ratios:
Diastatic power.
THE POWER OF MALT
Diastatic power (DP), also known as enzymatic power, refers to the malt’s ability to break down starch into simple sugars during the mashing process. It’s a measure of the alpha amylase enzyme, and the beta amylase enzyme, the two common enzymes brewers naturally call upon in the mash tun to convert their starch into sugar during the mashing process. These enzymes are also known as diastase enzymes, which is how we landed on the term ‘diastatic.’ Diastase enzymes most effectively work between 149–162 °F (65–72 °C). Without the appropriate amount of enzyme, your starch won’t turn to sugar, leaving you with a strange, sweet, low-alcohol beer. Understanding diastatic power and proper ratios will help avoid any grist issues. It’s the good way to determine if your mash will be happy and healthy, or whether it will take forever to complete the conversion of starch
to sugar.
Diastatic power is measured in degrees lintner (unless the malt is German, and then the units are Windisch-Kolbach). This is typically listed as “DP” on a malt specification sheet, or as a number with the abbreviation “°L” following. Keep in mind that an “L” without the degree symbol will probably mean lovibond, a measure of color, in relation to brewing. Generally, the minimum amount of DP needed to convert an entire mash tun of starch is 30 °L. This is quite low, and hard to achieve. Depending on your temperature, pH, and your ability to continually mix your mash to keep that small amount of enzyme moving around, conversion may take a while.
A good minimum for the homebrewer would probably be about 40 °Lintner. We’ll use this moving forward as our baseline for an appropriate mash target. Keep in mind, this means any malt that provides less than 40 °L of diastatic power would not be a great choice as the single malt in your recipe. Anything under 30 °L should be considered unusable on its own.
KILNED MALT IS KING
In terms of diastatic power, kilned malt is king. Kilned malt is the most common type of malt by volume, as it includes all of what would be considered your base malt varieties: 2-row, pale ale, Pilsen, Vienna, and Munich, among others. What makes many kilned malts suitable as base malts? Diastatic power. Base malt is anything you can rely on to convert starches into sugars in malt with low or no diastatic power. These are the “base” of any well thought recipe. They usually provide a sum inclusion rate of 51% or higher, the majority of the malt in your recipe. We’ll talk usage rates a bit later.
You can usually find the diastatic power of your malt on the website of the maltster. Other malts may undergo a process that will denature the enzymes, such as roasting. They may have the starch present, just no way to turn it into sugar. Some malts that may be low in enzyme, or have no enzyme, would be darker Munich malts, biscuit malts, amber malt, and brown malt. Dark roasted malts such as chocolate malt or black malt also have starch left to convert, but it will be less than lightly roasted malts.
DIASTATIC POWER FORMULA
When calculating diastatic power, our formula should look like this:
LB = Σ(LG x GW) / (BW)
LB = Lintner of batch
LG = Lintner of grain
GW = Grain weight
BW = Total batch weight
Let’s look at an example recipe grain bill (I’ll call it Ill Advised Brown Ale) and work through this calculation. In this example we will look at the weight in lbs. to keep the math simple, but it can be adjusted to metric
as well:
8 lbs. UK pale ale malt (DP 45 °L)
1 lb. Munich malt (DP 40 °L)
1 lb. caramel 80 L malt (DP 0 °L)
0.5 lb. Victory® malt (DP 0 °L)
0.5 lb. chocolate malt (DP 0 °L)
36.36 °L = (360+40+0+0+0=400)/11
In the formula above we took the diastatic power from the UK pale ale malt (45 °L x 8 lbs. = 360 °L) and the diastatic power from Munich malt (40 °L x 1 lb. = 40 °L). The three additional malts gave us no diastatic power. With the sum of our diastatic power now known to be 400 °L, we take the weight of the entire bill, 11 lbs., and divide by this. We’ll have a diastatic power of 36.36 °L for this batch. Less than the 40 °L we’d hope for. The answer could be as simple as a few pounds of a higher DP base malt in place of some of the pale ale malt, or a different pale ale malt with a higher DP altogether.
Let’s reformulate (this time for Right Ratio Brown Ale):
6 lbs. UK pale ale malt (DP 45 °L)
2 lbs. North American 2-row (DP 131 °L)
1 lb. Munich malt (DP 40 °L)
1 lb. caramel 80 L malt (DP 0 °L)
0.5 lb. Victory® malt (DP 0 °L)
0.5 lb. chocolate malt (DP 0 °L)
52 °L = (270 + 262 + 40 + 0 + 0 + 0 = 572)/11
With two pounds of North American 2-row substituted in for two pounds of the UK pale ale malt you can expect full conversion of your mash at 52 °Lintner.
STARCH AND SUGAR IN SPECIALTY MALT
Due to the higher heat used to create malts with darker colors and unique flavors, most of these specialty malts don’t contain any diastatic power. Many of these specialty malts provide less fermentable material as starches are converted to sugar during the process, like in caramel malt, or starches are carbonized and made non-fermentable, like in black malt. In most cases, the darker the malt, the less fermentable the malt will be.
Caramel malts strive to achieve the mashing process for you, inside the kernel. The malt is wetted and the temperature in the roaster held at a saccharification temperature (i.e. a temperature the diastatic enzymes work well at converting starches in to sugars), around 149 °F (65 °C), and the process is continued in the tiniest mash tun on earth, within the barley husk. Caramel malts can be steeped without the worry of diastatic power — helpful to extract brewers.
Some folks in the brewing industry choose to only formulate diastatic power based on the malt that has starch to be converted. Others argue that the total amount of malt matters in terms of enzymes. In other words, some believe that you could probably leave caramel malt out of the diastatic power equation if you wanted to, but most brewers prefer to err on the safe side when it comes to diastatic power available.
Other malts can be steeped without the help of diastatic power as well, though you’ll probably be wasting some starch inside. Often in malt extract-based recipes with steeping grains, malts such as chocolate will be used strictly for color, flavor, and aroma. There are other attributes the grain might lend without being converted like body, mouthfeel, and head retention.
RAW AND FLAKED MALTS
A time to be most aware of your diastatic power is when using raw or flaked grains. Raw grains have not undergone the malting process, which both creates a greater quantity of enzymes in the grain itself, and makes these enzymes accessible. Germinating (sprouting) the grains during the malting process both uses enzymes that were already available inside the seed, and also creates more enzymes to help the plant grow. The growth is stopped by way of a hot kiln, dried to preserve the enzyme package inside for the brewer. This drying also makes the grain shelf stable for a longer period of storage than would be possible if raw, sometimes up to 24 months if stored properly.
Raw grains are often referred to as “adjuncts.” These grains are meant to be used in addition to malt when brewing. They are typically used for specific beer styles, most commonly North American lagers, which generally include corn or rice. Some homebrewers use adjuncts when making a beer with homegrown or locally-grown grain as well. This is an appropriate time to check your math, and make sure you have enough enzyme to fully convert the raw grains in your recipe.
Keep in mind, when partial-mashing with specialty malts and flakes, the brewing process is a bit different. You’ll be relying on both malt extract and grain for your sugar, and it can be even more important to make sure your diastatic power is strong enough to convert your sugars. Think of malt extract as base malt that will provide your recipe with no diastatic power. Often partial mash recipe ratios lean toward more specialty malt than base malt, especially if the recipe is a conversion from an all-grain recipe, or an extract-based recipe with steeping grains. Converting starch to sugar may be a bit more challenging as ratios are skewed, so be sure to provide ample base malt.
USAGE RATES
When doing research on malts, you’ll see usage rates provided by the manufacturer that help you determine what’s an appropriate amount of a certain type of malt or grain.
Armed with this information, and what you’ve been told so far about diastatic power, it’s time to debunk a myth some brewers out there hold: You should never exceed the recommended usage rates of a malt. This is technically incorrect. Don’t get me wrong, these rates are there for a reason, but they are merely guidelines to keep you from going off the rails too far. The biggest reason usage rates are in place comes back to our pal, diastatic power. Without the proper enzyme package, your beer is going to be thick, sweet, and unfermentable.
The other major reason usage rates are in place would be what you might expect: Flavor and general usability. Some ingredients, such as flakes, will be a burden in most mash tuns, even at the maximum grist ratio of 40%. Other items, such as black malt, can create acidic and acrid flavors in your beer making it nearly undrinkable if used at higher levels than suggested.
Should any of these recommended usage rates stop you? No! Want to try 30% caramel malt? 50% flaked grain? Just be ready for flavors to be dramatically pronounced beyond what you’re used to in traditional styles of beer, and potential issues in both the mash tun and fermentation stage of your brewing process. Let the idea of going beyond these boundaries give you pause, though. Do the math on your diastatic power, and give it a go!
There are very few beer styles that take you out of diastatic power’s comfort zone. Most use high DP base malts to do the majority of starch conversion in a grain bill. It’s uncommon to see a beer style that can’t be formulated with at least 80% base malt, providing an ample amount of DP. Though, as mentioned above, if you like living on the edge, there’s no reason you can’t cut your base malt back to less than half of your grain bill. Who knows, you may end up creating a new style of beer altogether, just using ratios beyond what modern beer style guidelines and usage rates would hold you to.
REMEMBER TO CHECK YOUR RATIO!
Kilned base malts comprise a good portion of your grain bill for a reason. It’s not just stylistically accurate to use kilned base malts as the majority in most styles of beer, it’s just plain hard to brew without them. When first formulating recipes, use style guidelines to help direct your malt usage. You’ll have a better understanding of what the malt bill should be, and how the beer should turn out in terms of flavor. With an understanding of diastatic power, you’ll get the gist of your grist, and can successfully begin calculating malt bills for your own recipes!
