The balance between bitter hops and sweet malts has always been important in crafting world class beer. This week we take a look at the bitterness ratio and how you can use it to improve the balance of homebrewed beer recipes.
The sweetness of malted barley and specialty grains must be offset by bitterness. Early beers used all kinds of herbs including ginger, caraway, cinnamon, citron, coriander, juniper, mint, myrtle, saffron, hysop, dill, thistles, and many others to counterbalance the sweetness of malt. Most modern beers use hops for bitterness, though some specialty beers like Belgian Wit still make use of other spices.
The idea of trying to quantify the bitterness to sweet malt balance is also not new. English brewers regularly used “pounds of hops per quarter of malt” for the last several hundred years to characterize the hops-malt balance. Modern brewers started using the modern equivalent, called the bitterness ratio or BU:GU ratio many years ago. The measure, determined by simply dividing the number of IBUs in a beer by the number of gravity units, provides a rough estimate of the balance between hop bitterness and malt sweetness. It is featured in Ray Daniel’s Designing Great Beers book where he lists the average bitterness ratio for many popular styles.
To calculate the bitterness ratio we start with the number of international bitterness units or IBUs. For example, lets say we start with a beer that has 30 IBUs. We then take the original gravity of the beer (for example 1.048), take the fractional portion (0.048) and multiply by 1000 to get the number of gravity points. In this example 1.048 would simply be 48 points. Now we take 30 IBUs and divide by 48 points to get a bitterness ration of 0.63. If you are using BeerSmith, the estimated bitterness ration (IBUs/OG points) is displayed just below the color on the recipe design page.
Obviously the bitterness ratio needed varies depending on the style of the beer. A hoppy India Pale Ale is going to have a much higher desired bitterness ratio than a barely hopped Weizenbier. To determine the correct target bitterness ratio, one needs to know the average IBUs and starting gravity for different beer styles. Fortunately the BJCP style guideline provides just such a resource. To calculate your target average style BU:GU ration, determine the average IBUs for the style guide and divide by the average OG points for the style. I’ve calculated the bitterness ratio for a few popular styles here from the 2008 guidelines:
- American Amber: 0.619
- Bohemian Pilsner: 0.800
- Oktoberfest/Marzen: 0.449
- Traditional Bock: 0.346
- Blonde Ale: 0.467
- California Common: 0.735
- Ordinary Bitters: 0.833
- American Pale Ale: 0.714
- Brown Porter: 0.576
- Dry Irish Stout: 0.872
- English IPA: 0.800
- Weizen/Weissbier: 0.240
- Belgian Trippel: 0.375
The above is just a sampling, but gives us some idea of the range of average bitterness ratios for different styles. A higher bitterness ratio corresponds to more bitter beers overall. Not surprisingly many of the malty or high wheat German beers such as Weizen and Bock have low average bitterness ratios (0.240-0.345), while IPAs, Pale Ales, and those with high concentrations of dark malt such as stouts have much higher average ratios of 0.800 or higher. Many popular styles lie in the middle range of around 0.500, such as Oktoberfest, Porter, and Blonde Ale.
The bitterness ratio does not tell the whole story, however, as it does not take into account the individual grains making up the grain bill. For example Oktoberfest/Marzen has a malty flavor from its Munich malt grain bill base that is not reflected in its mid-range BU:GU ratio. Irish Stout, which requires a higher BU:GU ratio to balance its high concentration of black/stout roast malt has a relatively high 0.872 bitterness ratio, but the dry flavor of the roasted malt dominates the flavor profile more than hop bitterness.
Still, calculating the bitterness ratio for a given beer and comparing it to the average for your target beer style can help to create a beer with an appropriate flavor balance, especially when traditional ingredients are used. I personally like to do a sanity check on my bitterness ratio against the style guide to make sure I’m in the ballpark when creating a new recipe.
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