| UPDATE: This is an interesting 'guide' but I have found that its easy to fall outside the parameters just by yeast selection, i.e. attention changes. Also some quality brews produced by the likes Sierra Nevada don't comply with 'beer balance'. None the less its interesting. It can only advance the knowledge of brewing! |
| I found this on the net. Don't know who the authors are but their theory makes compelling reading and is something I will apply to my future brewing. There will be a BV (Balance Value) rate shown in all new recipes and any I rebrew. Also refer to the BJCP Guidelines. A handy PDF copy can be downloaded.
You can find a Beer Balance spreadsheet here to play with when tasting and designing new beers. It's a work in progrees but you can update it to suit your needs. |
Sweetness, Bitterness, and Balance |
| Hop bitterness and sweetness from unfermentable extract are two primary factors which determine a beers balance. Beers which are perceived as neither bitter nor sweet are termed in balance, though this is largely subjective and can mean different things to different people. Nevertheless, it is helpful to quantify the relationship between sweetness and bitterness, leaving the individual to decide what's balanced. In his excellent book, Designing Great Beers, Ray Daniels suggests looking at the ratio between a beer's International Bitterness rating (expressed in IBUs, mg of iso-alpha acid per liter of beer) to the beer's starting gravity expressed in 記eschle (what many people refer to as Gravity Units). He refers to this as the BU:GU (for Bittering Units to Gravity Units) ratio. |
The BU:GU Ratio |
| Let's consider three beers: a Bock, a Vienna, and a Dry Stout. Most people would say the Bock is sweeter than the others, the Dry Stout more bitter, and the Vienna somewhere in between. What do the numbers tell us? Check out the table below. |
| Bock | Vienna | Dry Stout | |
|---|---|---|---|
| IBU | 22 | 22 | 40 |
| OG,記e | 66 | 50 | 40 |
| BU:GU | 0.33 | 0.44 | 1.00 |
| Table 1. BU:GU Ratios for selected styles. | |||
| Most people would agree that these numbers track, at least in an ordinal sense, their perception of each beers bitterness relative to its sweetness. The Bock tastes the sweetest and it has the lowest BU:GU ratio; the Stout is the most bitter and it has the highest ratio. Seems to work great!
Nevertheless, some beers refuse to fit in. Consider a Dubbel. It should certainly be malty, but not especially sweet. Most experienced beer tasters would place a classic Dubbel between the Bock and the Vienna in terms of sweetness/bitterness balance. Let's see how a typical Dubbel fits in: |
| Bock | Dubbel | Vienna | Dry Stout | |
|---|---|---|---|---|
| IBU | 22 | 22 | 22 | 40 |
| OG,記e | 66 | 66 | 50 | 40 |
| BU:GU | 0.33 | 0.33 | 44 | 1.00 |
| Table 1a. BU:GU Ratios for selected styles. | ||||
| This says the Dubbel is as sweet as the Bock, and we know thats not the case. Dubbels are more balanced than Bocks, and closer, in terms of balance, to something between the Bock and the Vienna. The BU:GU ratio has, in this case, led us astray. That's surprising, as the BU:GU ratio has proven quite useful, and seems to work well for many beer styles. What went wrong? Can we do anything about it? |
Attenuation and Real Terminal Extract | |
| The three beers examined in Table 1 all had roughly the same Apparent Attenuation (AA), about 72 percent. We compute AA as: | |
| AA = (OG - FG) / OG | (1) |
| The BU:GU ratio works quite nicely for beers with similar apparent attenuation ratios. The Dubbel is highly attenuated, so its starting gravity belies its dryness relative to the Bock. Thus, the BU:GU ratio is less useful for beers which are relatively over- or under-attenuated. Can we take attenuation into account?
We refer to the ratio given in the formula above as apparent attenuation because it fails to account for two simple facts:
1. Some of the extract has been converted into alcohol; and We may approximate the Real Terminal Extract (RTE) with a formula by Balling (here, slightly simplified): | |
| RTE = (0.82 x FG) + (0.18 x OG) | (2) |
| We submit that RTE is a better measure of a beer's sweetness than its Original Gravity. | |
A New Measure of Balance | |
| In order to account for differing levels of attenuation, we replace the GU, the beers original gravity in 記e, with its Real Terminal Extract, expressed in the same units. For a reason we'll explain later, lets multiply the ratio by 0.8. We compute: | |
| BV = 0.8 x (BU / RTE) | (3) |
| where BV stands for Balance Value.
Because the RTE will never be higher than the OG, we shall wind up with a larger quotient. In fact, for beers with typical levels of attenuation, the new formula will give results which will be about twice as high as those given by the old one. This shouldn't bother us, as long as we recognize that the two formulae will produce numbers on different scales. How do the beers we've already examined rate in terms of their Balance Values? Let's compute them for our familiar examples as well as for a couple of extra styles (Dortmunder and Pilsener): | |
| Bock | Dubbel | Vienna | Dortmunder | Pilsner | Dry Stout | |
|---|---|---|---|---|---|---|
| IBU | 22 | 22 | 22 | 26 | 35 | 40 |
| OG,記e | 66 | 66 | 50 | 52 | 50 | 40 |
| FG,記e | 18 | 14 | 14 | 14 | 14 | 10 |
| RTE,記e | 26.6 | 23.4 | 20.5 | 20.8 | 20.5 | 15.4 |
| BV | 0.66 | 0.75 | 0.86 | 1.00 | 1.37 | 2.08 |
| Table 2. Balance Values for selected styles. | ||||||
| Here we see the proper ordinal relationship between the beers, particularly the first three. The Dubbel is essentially midway between the Bock and the Vienna in terms of its balance. This seems quite reasonable.
Why the factor of 0.8? With it, the Dortmunder, a beer which belongs to a style which the Beer Judge Certification Program (BJCP) Style Guidelines claim is balanced, has a Balance Value of one. Sweet styles will have lower Balance Values, and more bitter styles will have higher BVs. Here, we see a BV of 0.86 for the Vienna, which is slightly sweet, and a BV of 1.37 for the Pilsener, which is bitter. Not only does the 0.8 factor make the new values about double those produced by the old formula for beers with typical attenuation levels, but it places what many consider to be the line of demarcation between sweet and bitter very close to unity. Handy! |
Using The Balance | |
| There are a number of ways in which the Balance Value may be applied. One way is helpful in beer appreciation. Compare the Balance Values for several styles of beer. Compute the Balance Values for commercial examples when the necessary parameters are given, and taste the beers. See how the Balance Value tracks what you perceive as the balance between sweetness and bitterness.
Another application is in recipe formulation. When formulating a recipe, one usually starts with a target Original Gravity. If you know what apparent attenuation to expect, you can predict the Real Terminal Extract: | |
| RTE = OG x (1 - (0.82 x AA)) | (4) |
| where AA is the Apparent Attenuation, expressed as a decimal fraction. Typical values are 0.70-0.76, depending on the yeast strain and the fermentability of your wort, and other factors. If you have a Balance Value in mind (based, perhaps, on a commercial example you like, or computed from the mid-range of the parameters of the BJCP style guideline for the style you're brewing), you can compute a target Bitterness Level, in IBUs: | |
| BU = 1.25 x BV x RTE | (5) |
| Equations (4) and (5) may be combined: | |
| BU = 1.25 x BV x OG x (1 - 0.82 x AA) | (6) |
| You can then compute hopping rates according to your favorite method. | |
| Example | |
| Let's use Equation (6) to determine the bittering level of a Northern Brown Ale. We want an OG of 1.046 (46 記e), and an apparent attenuation of 0.74. The BJCP Style Guidelines say that a Northern Brown should possess a "Gentle to moderate sweetness . . . . Balance is nearly even". We want something that is leaning just a tiny bit towards sweet. Let's use a Balance Value of 0.97, which should be nearly even in balance. Plugging these figures into Equation (6) yields:
BU = 1.25 x 0.97 x 46 x (1 - 0.82 x 0.74) = 1.25 x 0.97 x 46 x 0.3932 = 21.9 We would round this to 22 IBU, which we see is near the middle of the range of 15 to 30 IBU. | |
Conclusion | |
| A new method of computing a beer's balance between sweetness and bitterness was presented. It accounts for attenuation, as well as the beer's original gravity and bittering level. The new value is referred to as the Balance Value, and assumes values close to unity for beers which many regard as balanced. It is computed from the beers original and final gravities, expressed in 記eschle (Gravity Units), and the beers bittering level, expressed in International Bittering Units (IBUs).
Practical applications of the new quantity were briefly discussed. The metrics use in determining a bittering level in recipe formulation was illustated through an example. The new value does not take into consideration complex factors, such as ester levels and types, roastiness, phenol concentration, and how the terminal extract is distributed between sweet and flavorless components. Therefore, it cannot be expected to perform perfectly. Rather, it is offered as an improvement over an existing formula which has proven quite useful. Hopefully, the new value will prove even more useful. Finally, it was suggested that the logarithm of the Bitterness Value would better track the perceived balance. This has the advantage of placing the balance point at or near zero, with sweet beers having negative log Balance Value, and bitter beers having positive log Balance Values. We think that the BU:GU ratio is a useful tool. Like nearly any simple formula not derived from first principles, it has numerous limitations. Yet, in spite of these, it has served the craft and homebrewing communities well. Our aim here was to provide an alternative which remains almost as simple, but is more robust (and, hence, hopefully even more useful), not to rip apart someone else's suggestion. We're building on someone else's suggestion. And that's how progress is made. |
| *** Also see Attenuation from Realbeer. It explains that 0.8 that mysteriously appeared in the above formula and Real Attenuation. |