Section 3 – Brewing All-Grain Beer
Chapter 18 - What to Expect When You are Extracting
Okay, now we are getting down to brass tacks. We have identified the different kinds of malts and adjuncts that can be used to make the wort. We have described how the enzymes in the malt are activated during the mash and convert the available starches to fermentable sugars. We have discussed the different methods of mashing and the different methods for separating the wort from the spent grains. Now it is time to put all of this information together and figure out how much wort we are going to get from our efforts. To brew the same beer recipe consistently, or to brew a new recipe right the first time, we need to know how much yield we can expect from each type of grain. Then once we know the potential, we need to be able to measure how much extract we actually achieve from our mashing and lautering process and calculate our brewing efficiency.
The first question is how much is available?
The answer to this question is contained in a malt analysis sheet. These information sheets from the maltster describe the amount of extract that each lot of malt can yield. Typical analysis for the malt type should be available over the Internet from the maltster, and a lot-specific analysis may be available at your local brew shop where you buy the grain. (Usually, you don’t need to get lot-specific data.) Unfortunately, calculating your OG from several malt analysis sheets is not as straightforward as calculating it for malt extract. When you target an OG with malt extract, it’s as simple as multiplying the weight of the extract in pounds by its yield (36 gravity points per pound per gallon for liquid malt extract or 42 PPG for dry) and dividing by the recipe volume. For example, 6 pounds of liquid malt extract (36 PPG) for a five gallon batch equals an OG of 6 x 36 / 5 = 43.2 or 1.043. To calculate an OG from the yield information on a malt sheet, we will need to convert that information to potential gravity points (i.e., PPG) and learn how to calculate an efficiency factor that adjusts that yield to our brewery’s process capability. Once we understand malt yield and efficiency, we will be able to calculate a grain bill to hit any gravity.
Malt Analysis Sheet review
Extract: Fine Grind, As-Is, and Dry Basis
A malt analysis sheet does not give the malt’s yield in points per pound per gallon. Instead, what you will most likely see for North American and European malts is a weight percentage called %Extract– Fine Grind, Dry Basis (FGDB). This percentage is the maximum soluble extract that the malt can yield when mashed.
When a malting house analyzes a malt sample to determine its extract yield, it conducts a laboratory mash, known as a “Congress mash” (named for the European Brewing Convention (EBC) of 1975 which standardized the procedure). A Congress mash consists of a multi-infusion mash using a standard weight of finely ground malt. This procedure yields the maximum soluble extract as a weight percentage of the original sample. This yield is known as the %Extract–Fine Grind, As-Is (FGAI). It is called “As-Is” because properly kilned malt contains about 4% moisture by weight, although it can range from 2-10%. To compare different lots of malt with different moisture levels, this weight needs to be accounted for in the extract calculation. Therefore, the basis of comparison, and the number you will most consistently see on an analysis, is the Fine Grind, Dry Basis (FGDB)— corresponding to a malt that has been oven-dried to zero moisture. I will explain how to use these numbers in your OG calculations in a minute, but first let’s look at the other extract parameters you may see.
Converting %Extract to PPG
In a Congress mash, each grain will yield a maximum amount of fermentable and non-fermentable sugars that is referred to as its percent extract or maximum yield. This number typically ranges from 60-80% by weight, with some wheat malts hitting as high as 85%. For example, 80% Extract means that 80% of the malt's weight is soluble and extracted by the laboratory mash and lauter. (The other 20% represents the husk and insoluble proteins and starches.) In the real world, homebrewers will never hit this target, but it is a useful basis for comparison.
The reference for comparison is pure sugar (sucrose) because it yields 100% of its weight as soluble extract when dissolved in water and has no moisture of its own. One pound of sugar will yield a specific gravity of 1.046 when dissolved in water to form 1 gallon of solution. To calculate the maximum yield for different malts and adjuncts, the %Extract FGDB for each is multiplied by the reference number for sucrose—46 points/pound/gallon (PPG). For example, let's consider 2 Row Lager Malt. This base malt has an FGDB of 81.7% by weight of soluble materials. So, if we know that sugar (sucrose) will yield 100% of its weight as soluble sugar and that it raises the gravity of the wort by 46 PPG, then the maximum increase in gravity we can expect from this malt, at 81.7% soluble extract, is 81.7% of 46 or 37 PPG.
Hot Water Extract (HWE)
This parameter is used on malt analysis from the UK, where the Institute of Brewing (IOB) utilizes a single temperature infusion mash that differs from the ASBC and EBC Congress mash methods. Method 2.3—Hot Water Extract of Ale, Lager, and Distilling Malts, uses an hour long mash at 65°C (149°F) to measure the maximum extract. HWE (As-Is) is measured as Liter•Degrees/Kilogram, and as a unit, it is equivalent to PPG when the metric conversion factors for volume and weight are applied. (Note: points/pound/gallon = gallon•degrees/pound). The overall conversion factor is HWE = 8.345 x PPG. However, the grind/mash procedures for HWE and %Extract differ enough that the measurements are not actually equivalent, even though they are close. The best analogy I can think of is the trying to compare the power ratings of a racecar to a farm tractor—power is power, but the way it is expressed and utilized is different. That being said, if you get a malt sheet for Pale Ale malt with an HWE (As-Is) of 308 liter°/kg, the conversion of that number by 8.345 to 37 PPG is close enough for homebrewing purposes. Finally, I want to point out that HWE is really a more realistic and practical yield number for home and craft brewers who are typically conducting single temperature infusion mashes for their beers.
Extraction Efficiency and Typical Yield
The maximum yield is just that, a value you might get if all the mash variables (e.g. pH, temperature, time, viscosity, grind, phase of the moon, etc.) lined up and 100% of the starches were converted to sugars. But most brewers, even commercial brewers, don't get that value from their mashes. Most brewers will approach 70-85% of the maximum yield (i.e., 70% of a malt’s FGDB of 81.7%). You may be wondering how useful the maximum yield number of a malt can be if you can never expect to hit it. The answer is to apply an efficiency factor to the maximum yield and derive a number we will usually achieve – a typical yield.
This factor is called the brewer's extract efficiency and it’s the ratio of his yield to the malt’s maximum yield (FGAI). Every brewery is unique and your extract efficiency is dependent on your methods and equipment. I will show you how to calculate your efficiency in the next section. The As-Is and Dry Basis PPG’s at 75% Efficiency are listed in the last two lines of Table 26. The As-Is value, which accounts for moisture, is preferred for estimating your yield, but it may not always be listed on an analysis. You can estimate the As-Is value from the Dry Basis and %Moisture numbers. If your extract efficiency is high, (near 90%), then you can figure on losing 1 PPG for every 3% moisture; if your efficiency is lower (about 75%), then you will lose 1 PPG about every 4%.In Table 27, we assume an extract efficiency of 75%, which is considered average for homebrewers using a batch sparge technique with current malts. A few points less yield (i.e. 70% extraction efficiency), is still considered to be good extraction. A large commercial brewery would see the 5% reduction as significant because they are using thousands of pounds of grain a day. For a homebrewer, adding 5% more grain per batch to make up for the difference in extraction is a pittance.
Calculating Your Efficiency
There are two different gravities that matter to a brewer: one is the extraction or boil gravity (BG), and the other is the post-boil or original gravity (OG). Most of the time, people refer to the OG because it determines the strength of the beer. When brewers plan recipes, they think in terms of the OG, which assumes that the wort volume is the final size of the batch, e.g. 5 gallons.But when it comes to the extract efficiency, we want to think in terms of the boil gravity because that volume of wort and its gravity is our actual yield. When all-grain homebrewers get together to brag about their brewing prowess or equipment and they say something like, "I got 30 (PPG) from my mash schedule", they are referring to their yield in terms of the amount of wort they collected.
It is important to realize that the total amount of sugar is constant, but the concentration (i.e. gravity) changes depending on the volume. To understand this, let's look at the unit of points/pound/gallon. This is a unit of concentration, so the unit is always expressed in reference to 1 gallon ("per gallon"). Another way of writing this unit is gallon•degrees/pound. When mashing, you are collecting "x" gallons of wort that has a gravity of “1.0yy” that was produced from "z" pounds of malt. To calculate your mash extraction in terms of PPG, you need to multiply the number of gallons of wort you collected by its gravity and divide that by the amount of malt that was used. This will give you the gravity (gallon•degrees), per pound of malt used. Let's look at an example.
Grain bill for Palmer’s Short Stout(Yield = 6 gallons of 1.038 wort) 6.5 lbs. of 2 Row0.5 lb. of Caramel 150.5 lb. of Caramel 750.5 lb. of Chocolate Malt0.5 lb. of Roast Barley(8.5 lbs. total)
For our example batch, we will assume that 8.5 pounds of malt was mashed to produce 6 gallons of wort that yielded a gravity of 1.038. The brewer's total sugar extraction (yield) for this batch would be 6 gallons multiplied by 38 points/gallon = 230 points. Dividing the total points by the pounds of malt gives us our mash extraction in points/pound e.g. 230/8.5 = 27 PPG. Comparing these numbers to lager malt’s maximum 36 PPG (As-Is) gives us a good approximation of our mash efficiency: 27/36 = 75%.
If we look at the maximum PPG As-Is numbers from Table 26 for each of the recipe’s malts, we can calculate our actual mash efficiency:Malts Max. PPG (As-Is)6.5 lbs. of 2 Row 36 x 6.5 / 6 = 390.5 lb. of Caramel 15 34 x .5 / 6 = 2.80.5 lb. of Caramel 75 35 x .5 / 6 = 2.90.5 lb. of Chocolate Malt 34 x .5 / 6 = 2.80.5 lb. of Roast Barley 30 x .5 / 6 = 2.5Maximum Yield (As-Is) 50 points or 1.050In this case, our mash extraction of 1.038 means our actual efficiency was 38/50 = 76%.
Table 26 – Extract Analysis Data for several malts
The percentage of soluble extract by weight is given for several common malts with the equivalent value in points/pound/gallon (i.e., gallon•degrees/pound) given in parentheses.
Table 27 – Typical Malt Yields in PPG
Planning Malt Quantities for a Recipe
We use the efficiency concept in reverse when designing a recipe to achieve a targeted OG. How much malt do we need to produce five gallons of 1.050 wort?
Let’s go back to our Short Stout example. 1. First, we need to assume an efficiency (e.g. 75%) for our primary malt (78% FGAI) and calculate an anticipated yield. 78% x 75% x 46 (PPG/100% sucrose) = 27 PPG
2. Then we multiply the target gravity (50) by the recipe volume (5) to get the total amount of sugar. 5 x 50 = 250 pts.
3. Dividing the total points by our anticipated yield (27 PPG) gives the pounds of malt required. 250 / 27 = 9.25 lbs. (I generally round up to the nearest half pound, i.e., 9.5 lbs.)
4. So, 9.5 lbs. of malt will give us our target OG in 5 gallons. Using the malt values for 75% Efficiency in Table 27, we can figure out how much of each malt to use to make up our recipe. You can build a grain bill “top-down” or “bottom-up,”—meaning that you can plan the bulk of your fermentables from the base malt first, and adjust the specialty grains to make up the rest, or you can plan your specialty grain additions first, and use the base malt to complete the OG. I generally use the bottom-up approach and, for this example, I am going to use a half pound of each specialty malt, and then calculate how much base malt I need to hit my target gravity.
Specialty Malt OG Contributions based on PPG, As-Is at 75% Efficiency Caramel 15 26 x .5 / 5 = 2.6Caramel 75 25.5 x .5 / 5 = 2.6Chocolate Malt 21 x .5 / 5 = 2.1Roast Barley 19 x .5 / 5 = 1.9 9.2 points out of 50
To calculate how much base malt is required, subtract the specialty malt contribution from the total, multiply that amount by the recipe volume and divide that by the base malt’s 75% PPG number (28).
(50 – 9.2) x 5 gal. ÷ 28 = 7.3 lbs. of base malt, which I would round up to the nearest half pound for convenience sake (7.5 lbs.)
Thus, the grain bill for Palmer’s Short Stout, based on these particular lots of malt and 75% extract efficiency is:2 Row Lager malt 7.5 lbs.Caramel 15 0.5 lbs.Caramel 75 0.5 lbs.Chocolate Malt 0.5 lbs.Roast Barley 0.5 lbs. For a total of 9.5 lbs.Remember though that this is the OG— the post-boil gravity. When you are collecting your wort and are wondering if you have enough, you need to ratio the measured gravity by the amount of wort you have collected to see if you will hit your target after the boil.
For instance, to have 5 gallons of 1.050 wort after boiling, you would need (at least): 6 gallons of 1.042 (250 pts/6 gal.)or 7 gallons of 1.036 (250 pts/7 gal.)
Using Liter Degrees per Kilogram (PKL)
The concepts work the same with Hot Water Extract and Liter°/kg (aka. Points per Kilogram per Liter). The HWE value for pale ale malt in Table 26 is 310 PKL.
To calculate the weight of pale ale malt for 20 liters of a 1.045 OG wort:1. 20 L x 45 = 900 gravity points2. If we assume the same 75% brewer efficiency, 310 HWE for the pale ale malt becomes 232.5 L°/kg.3. Dividing the gravity points by the HWE gives the weight of malt in kilograms. 900/232.5 = 3.87 kg.To calculate your actual brewing efficiency for a batch, let’s say we collected 28 liters of 1.042 wort from 5 kg of pale ale malt (310 HWE fgdb). 1. 28 L x 42 pts = 1176 gravity points (or L°)2. 1176 / 5 kg = 235 L°/kg3. 235 / 310 = .758 or 76% efficiency.
Using °Plato
You may have a hydrometer or refractometer that measures in °Plato instead of specific gravity (SG). Refractometers are based on the Brix scale which is functionally equivalent to °Plato. You have two options for calculating your brewing efficiency and malt quantities when measuring in °Plato:1. Convert the °Plato to specific gravity (See table 31 in Appendix A) and estimate your malt quantities and efficiency using the PPG and HWE methods described above.2. Use the °Plato and the extract weight-percent method to calculate these quantities.Degrees °Plato measures the amount of extract in wort as a weight percentage (solute:solution). In other words, a wort that measures 10 °Plato has 10 grams of soluble extract (sugars, carbohydrates, proteins and lipids) in 100 grams of wort. Commercial breweries use this unit more often than PPG or HWE to figure malt quantities because it gives them better visibility to their malt usage, being malt weight-oriented rather than wort volume-oriented.
To calculate your brewing efficiency using °Plato, the equation is:Brewing Efficiency = wt. of actual extract/ wt. of maximum extract Brewing Efficiency = (wort volume x wort density x wt. % extract in the wort)/(malt wt. x maximum yield)
So what we are doing is calculating the actual weight of the extract in the wort, compared to the maximum extract we could have gotten from the grain bill. The weight of the actual extract is calculated by multiplying the volume of wort by its density to get the total weight of the wort, and then using the measured °Plato to say how much of that total weight is extract. The density of the wort is equal to the density of the water (1 kg/liter or 8.32 lbs./gal) multiplied by the specific gravity of the wort. (Specific gravity is actually a ratio of the solution’s density to the density of pure water.) To get the specific gravity value for the wort, you either have to measure it separately with another hydrometer or convert the °Plato reading to specific gravity using the ASBC tables in Appendix A. The conversion between °Plato and specific for worts less than 13°P is simply the gravity points divided by 4 i.e., 1.040 = 10°P, although the error increases at higher gravities.
The maximum yield weight is simply the weight of malt multiplied by the maximum yield e.g. 80% Extract FGDB. Then the equation becomes:Brewing Efficiency = [(Wort Volume x Water Density x SG) x °Plato] / (Malt(kg) x % FGDB)
For example, let’s say we used 4 kg of malt to brew 20 liters of wort that measures 12°P.
Using the rule of thumb for worts less than 13°P, the specific gravity is 1.048.
The brewing efficiency equation is:%Efficiency = [(20 L x 1 kg/L x 1.048) x 12%] / (4 kg x 80%) = 78.6%
The equation can also be re-arranged to calculate the grain bill necessary to brew 20 liters of a 12 P wort. For this example, let’s use our standard brewing efficiency of 75%. The equation becomes:Malt (kg) = [(Wort Volume x Wort Density x SG) x °P] / (% FGDB x Efficiency)Malt (kg) = [(20 L x 1 kg/L x 1.048) x 12%] / (80% x 75%)Malt (kg) = [(21 kg wort) x 12% extract by weight] / (60%) = 4.2 kg of malt Notes:1. The calculations can also be conducted in gallons and pounds by using the water density constant of 8.32 lbs. per gallon.2. I should mention that commercial brewers are most likely to use the coarse grind, as-is (CGAI) number from the malt lot analysis sheet, because that number takes the moisture loss into account, and helps them more accurately plan their malt usage and maintain better process consistency. On a homebrewing scale, we can be less rigorous and base our efficiency on the more readily available FGDB number. To take moisture into account, multiply the dry basis number by the percentage of dry weight. For example, 80% FGDB at 4% moisture becomes:80% x 96% = 76.8% FGAI If the F/C difference of the malt is 1.2%, then the CGAI would be:76.8% - 1.2% = 75.6%Substituting this CGAI number for FGDB into the malt quantity calculation above gives 4.4 kg required versus 4.2 kg. (Although if you recalculate your brewing efficiency using 4.2 kg and 75.6% CGAI, your brewing efficiency jumps up to 79.2%. It depends on whether you want to take the moisture of each lot of malt into account outside of your brewing efficiency, or just assume that the moisture content is going to be fairly consistent across different lots of malt, and take it into account as part of a lower overall brewing efficiency.)
The equation can also be re-arranged to calculate the grain bill necessary to brew 20 liters of a 12 P wort. For this example, let’s use our standard brewing efficiency of 75%. The equation becomes:Malt (kg) = [(Wort Volume x Wort Density x SG) x °P] / (% FGDB x Efficiency)Malt (kg) = [(20 L x 1 kg/L x 1.048) x 12%] / (80% x 75%)Malt (kg) = [(21 kg wort) x 12% extract by weight] / (60%) = 4.2 kg of malt Notes:1. The calculations can also be conducted in gallons and pounds by using the water density constant of 8.32 lbs. per gallon.2. I should mention that commercial brewers are most likely to use the coarse grind, as-is (CGAI) number from the malt lot analysis sheet, because that number takes the moisture loss into account, and helps them more accurately plan their malt usage and maintain better process consistency. On a homebrewing scale, we can be less rigorous and base our efficiency on the more readily available FGDB number. To take moisture into account, multiply the dry basis number by the percentage of dry weight. For example, 80% FGDB at 4% moisture becomes:80% x 96% = 76.8% FGAI If the F/C difference of the malt is 1.2%, then the CGAI would be:76.8% - 1.2% = 75.6%Substituting this CGAI number for FGDB into the malt quantity calculation above gives 4.4 kg required versus 4.2 kg. (Although if you recalculate your brewing efficiency using 4.2 kg and 75.6% CGAI, your brewing efficiency jumps up to 79.2%. It depends on whether you want to take the moisture of each lot of malt into account outside of your brewing efficiency, or just assume that the moisture content is going to be fairly consistent across different lots of malt, and take it into account as part of a lower overall brewing efficiency.)
Summary
So there you have it, the key to understanding malt yield, extract efficiency, and determining your grain bill for all-grain brewing. A malt analysis sheet will list the maximum yield as %Extract, Fine Grind, and we can convert that weight percentage to specific gravity points, or HWE, or °P. By comparing the collected wort gravity with maximum calculated yield, we can determine our extract efficiency, and by knowing our efficiency, we can calculate a grain bill for any wort we want to brew. Cheers!