Chapter 12 - What is Malted Grain?
12.3 Extraction and Maximum Yield
All of these grains can be used to produce the fermentable sugars that make up the wort. But to brew the same beer recipe consistently, we need to be able to quantify how much yield we can expect from each type of grain. Under laboratory conditions, each grain will yield a typical amount of fermentable and non-fermentable sugars that is referred to as its percent extraction or maximum yield. This number ranges from 50 - 80% by weight, with some wheat malts hitting as high as 85%. This means that 80% (for example) of the malt's weight is soluble in the laboratory mash. (The other 20% represents the husk and insoluble starches.) In the real world, we brewers will never hit this target, but it is useful for comparison.
The reference for comparison is pure sugar (sucrose) because it yields 100% of its weight as soluble extract when dissolved in water. (One pound of sugar will yield a specific gravity of 1.046 when dissolved in 1 gallon of water.) To calculate the maximum yield for the malts and other adjuncts, the percent extraction for each is multiplied by the reference number for sucrose-46 points/pound/gallon (ppg).
For example, let's look at a typical pilsner base malt. Most light base malts have a maximum yield of 80% by weight of soluble materials. So, if we know that sugar 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 pilsner base malt, at 80% solubility, is 80% of 46 or 37 ppg.
The typical maximum yields for the malts are listed in Table 9. 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 a scaling factor to the maximum yield and derive a number we will usually achieve - a typical yield.