(Last Updated On: January 2, 2019)

Bitterness is a crucial component for most modern beer styles. Even at low levels, bitterness plays an important role in recipe design. But what makes beer bitter?

What Makes Beer Bitter?

First and foremost, bitterness in modern beer comes from hops. Hops have many compounds and properties that make them great for brewing, but the primary contributors to bitterness are known as alpha acids.

We’ll talk more about alpha acids in a bit, but first it’s important to understand that hops are a major ingredient in most modern beer styles. Even those that are not considered bitter or “hoppy” styles.

Side note: There is a big difference between bitterness and “hoppiness” in beer… keep reading….

Other ingredients can also contribute to bitterness in beer. Roasted grains, coffee, or other adjuncts all impart flavors than can add to perceived bitterness. But hops are the primary bittering agent for beer.

Even if you don’t perceive a certain beer to be “bitter”, some degree of bitterness is built into the recipe to balance the malty sweetness.

Why Are Hops Used In Beer?

Hops are the main contributor to bitterness in modern beers

Hops have an interesting and ever-evolving role in beer, brewing, and even agriculture.

While the focus of this article is bitterness in beer, let’s take a slight detour and discuss the historic and modern uses of hops in brewing.

History of Hops in Beer

Beer was being made in some form or another long before hops became such an important ingredient.

In fact, some form of beer was being produced for as much as 8000 years before hops became a major ingredient in beer! Only in the last 200 years or so have hops become one of the big 4 main ingredients in beer.

Prior to hops, beer was typically dosed with a combination of spices, herbs, and fruit known as “gruit”. This added some flavor, and for a time in England brews made with Gruit were known as “Ale”, while hopped versions were known as “beer”.

See the resources section at the end of this article for more info on this topic. It gets deep, and is very interesting.

Hops as a Preservative

Eventually, brewers noticed that brews containing hops were less prone to spoilage than those made with Gruit or other herbs.

This improved storage life led to a greater proliferation of hopped beers around the world, as highly hopped beers could now be shipped on long voyages. When these beers arrived on the shores of distant lands not only unspoiled, but still fresh enough to be enjoyed, it’s easy to see how important hop additions became.

As a matter of fact, hops became so important to shipping beers over long distances that a very popular style was born. IPA, or India Pale Ale.

Hop Bitterness

Hops contain resin glands that contain a substance known as Lupulin. Luplin is primarily made up of compounds known as alpha acids.

Alpha acids become isomerized during the brewing process. and the newly formed iso-alpha acids are what contribute to the hop bitterness of a beer.

Interestingly, brewers now have access to concentrated Lupulin in powder and pelletized forms, which allow them to get the same bitterness, flavor, and aroma using only about 50% of the solid mass. This relatively new product is known as Cryo Hops or LupuLN2.

Check out: What are Cryo Hops

It was originally the bitterness and preservative effects of hops that first made them attractive to brewers, but now the delicious flavors and aromas of different varieties are just as important when creating hop-forward styles like American Pale Ales, IPAs, etc.

In fact, these days some hop varieties are grown primarily for the purpose of bittering, while other hops are prized for their flavor and aroma.

What Are IBUs In Beer?

Brewers around the world use a measure known as IBUs to design and describe the bitterness level of a recipe. IBU is an acronym for “International Bitterness Units” (also known as “International Bittering Units“).

This is an absolute, objective measurement of the compounds that contribute to bitterness in beer.

Unfortunately, it’s difficult for home brewers to actually measure the IBU level of a beer. Especially when compared to things like specific gravity.

Measuring IBUs requires lab equipment, while specific gravity can be accurately measured with inexpensive tools such as a hydrometer or refractometer.

Luckily, bitterness (in the form of IBUs) can be predicted via specific formulas, which are used by various brewing calculators to estimate the bitterness of a finished beer.

What Is The IBU Scale?

The IBU scale is a standard developed to describe the absolute bitterness of a beer, by measuring the amounts of iso-alpha acids in the beer.

Generally speaking, humans cannot reliably detect bitterness over 100 IBUs.

Common beers on the market will fall between 5 and 100 IBUs, while the majority fall into a narrower range than that.

Hops, Alpha Acids, and Bitterness

Hops contain alpha acids, which become isomerized (turned into iso-alpha acids) when exposed to heat.

The amount of Alpha Acids in a given hop variety determine the bittering potential of that hop. The true bitterness achieved will depend on how much of that potential becomes isomerized during the brewing process (in particular the boil).

Measured vs Perceived Bitterness

It’s important to note that the measured (or predicted) IBU level of a beer does not necessary describe the PERCEIVED bitterness on the palate.

Most of the mass-market light lagers that are popular in the US have a very low bitterness level. Usually between 5 and 12.

This is because these beers are designed to have very little flavor in general, with only enough hops used to balance whatever malt/adjunct flavor is present.

A beer with lots of malt character would be perceived as quite sweet with such a low IBU rating.

The specific gravity (a measure of the density of sugars and other compounds in a solution) plays an important role in the perceived bitterness of a beer.

For example, a very rich, malty style like an Imperial Stout will have a very high starting and finishing gravity. This gives the beer a very strong malty, flavor. To balance this and prevent the beer from tasting too sweet, a relatively high IBU level is necessary. These beers may have as much as 50-90 IBUs, but will taste less bitter than a lighter style with only 30 IBUs.

The balance of ingredients, gravity, and IBUs will determine the perceived bitterness of any beer.

Balancing Bitterness In Beer

As I mentioned, there is much interplay between the gravity of a beer and the bitterness level.

Generally speaking, the higher the gravity, the more IBUs will be required to maintain a ‘balance’ between the malty sweetness and the hop bitterness.

Bitterness To Gravity Ratio ( BU:GU )

Each beer style has an appropriate correlation between the OG (original gravity) and the IBUs of a beer, which we will refer to as the Gravity to Bitterness Ratio.

We can calculate this ratio with a simple formula:

Ratio = IBU / Gravity Points

Where: Gravity Points are the fractional portion of the OG multiplied by 1000.

For example, let’s assume a beer has an OG of 1.050 and 30 IBUs. The gravity points would be .050 * 1000, or 50.

30 IBUs divided by 50 Gravity Points would reveal a Gravity To Bitterness Ratio of 0.6.

A rough (but useful) rule of thumb is that a ratio of 0.5 would be perceived as balanced between sweetness and bitterness.

Depending on the style, the target ratio may be higher or lower.

If you don’t want to do this calculation yourself, I’ve got you covered with this gravity to bitterness ratio calculator.

Bitterness Ratio By Style

The above mentioned bitterness ratio calculator also has some example bitterness ratios for common and popular beer styles. I’ll include that table here as well.

BU:GU Ratio Of Common Beer Styles

Beer Style Common BU:GU Ratio American Light Lager 0.30 American Wheat Beer 0.47 German Pils 0.66 Irish Red Ale 0.56 Irish Stout 0.65 American Amber Ale 0.65 American IPA 0.95

Resources

I got a lot of information for this article from these fantastic resources you may want to check out.

https://www.chowhound.com/food-news/55095/what-does-india-have-to-do-with-india-pale-ale/

https://www.thebrewenthusiast.com/ibus/

https://en.wikipedia.org/wiki/Hops

http://www.beerscenemag.com/2010/04/the-short-and-bitter-history-of-hops/

Conclusion

I hope this article and the linked resources helped you learn something about modern and historical uses of hops in beer, calculating bitterness, or whatever else you wanted to know.

Please leave me a comment if you were looking for any information I didn’t include in this article!





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