IBUs: Measure & Calculate The Right Way

by Karl | Updated: March 3, 2020

IBU

IBU, short for International Bitterness Unit, was introduced as a chemical measurement for the number of bittering compounds used in the brew during the bittering process. This unit of measurement can be widely seen nowadays, printed on the labels of bottles and cans.

The measured IBU scale can range from 0 to infinity.

There is no maximum since a brewer could add more and more bittering compounds to make the beer more bitter. There are documented beers with 1000 measured IBUs but are very rare. The acid Iso-humulone found in hops gives beer its bitterness. Hops also contains beta acids that undergo oxidation and slowly contribute to the bitterness of the beer.

Many, though, love it as its bitterness tastes harsher. This oxidation occurs through fermentation, storage, and aging. At the same time, alpha acids undergo degradation to reduce the overall bitterness. Brewers use IBU as it has the closest correlation with the sensory bitterness of beer as a quality control tool. Brewers need to ensure formality and quality with each batch produced.

Typically, beers have an IBU ranging from 5 (very low bitterness) to 120 (very high bitterness). Most beers, however, have an IBU of 15 to 80. 

Try this IBU Calculator out for yourself.

Measuring Beer

There are many aspects of a beer that can be measured and quantified to estimate the quality of a perfect brew. Principally, the variety of flavours and intensity, bitterness, alcohol content, and color can be quantified. Before the early 20th century, there was no way to quantify the bitterness units of beer.

It’s just like there is no way to measure how ‘comfortable’ your favorite shoes are. It is about perception. 

Spectrophotometry

These technique measures beer bitterness units by the number of iso-alpha acids produced in the beer during the brewing process. The most common way to do this is through spectrophotometry. During the boiling process, hydrophobic properties of the iso-alpha acids are increased via reducing the pH levels by acid. An organic solution is then added so that the alpha acids shift out of the aqueous wort into the organic layer.

A spectrophotometer measures the absorbance – which is at 275nm. It is the wavelength where iso-alpha acids have the highest absorbance. With this, we can calculate the concentration of bittering molecules. Other techniques used are such as HPLC, mass spectrometry, and fluorescence spectroscopy.

Importance of IBU

It is important to note that IBU levels do not necessarily reflect the overall taste of beer as it is about the balance of ingredients and taste. For example, brews with more roasted malts or strong flavours will need a higher proportion of bittering agents. This is because strong flavouring agents cancel out the bitterness.

To illustrate, a pale lager with an IBU of 30 might taste more bitter than an imperial stout with an IBU of 50, due to its lower flavor intensity. It is also important to note that after 100 IBUs, our taste buds cease to tell the difference in bitterness despite adding more hops into to increase bitterness.

Although generally used by breweries as a quality control tool, this information can also be useful for consumers. While they do not affect the taste of beer, knowing the IBU of the Beer you drink can help you find your preferred IBU zone and build your own beer palate.

At the end of the day, these measurements help consumers find a sweet spot by matching preferences to the measurable facts displayed for your information.

IBU Charts

Here’s a handy reference IBU graph of the aveage by beer style that will give you a good idea of where your own recipes fall into the IBU scale.

The Ingredients & Brewing Process that Effect IBU’s

Beer comes in all forms of shapes and sizes and is widely enjoyed by everyone around the globe. Dubbed the third most popular drink after water and tea, beer pairs well with all sorts of events from lush parties to small gatherings at home.

Millions love the drink, whether while hanging around the bars or just enjoying some time alone. Major sporting events around the world, including football and rugby, have beer companies as sponsors.

Interestingly, the brew is also one of the oldest alcoholic beverages in the world. Even the Code of Hammurabi, as archaeologists discovered, had included laws on the regulation of beer and beer parlours.

Today, the drink is easily accessible and can be found in convenience stores everywhere. There are many ways to describe beer from its taste, color, to its strength. Citrusy, spicy, earthy, and aromatic are fancy all words used to describe the bitterness of a pint of lager. 

However, there is a unit measurement to quantify the bitterness of beer called IBU. While not a widely used unit of measurement, people who work in the beer industry, as well as beer connoisseurs, are no strangers to it.

Beer brewing process

So, what does your favorite brew have? Here is a look at the process in detail.

Malt

Brewing refers to the process of making the beer. All the ingredients are mixed together and left to ferment for a period. The essential ingredients to making beer are a starch source, yeast, and water. The starch source is the main factor affecting the strength and flavour of beer, and cereal grains are usually the first choice.

Most widely used grains include malted barley, though wheat, maize, and rice. Some brews can also be made with a secondary carbohydrate source, which is termed an adjunct. There are also other less widely used sources such as millet, cassava root in Africa, potato in Brazil, or agave in Mexico.

Most breweries these days use malted barley as its husk offers protection against damage as well as acting as a filter for better fermentation and subsequent flavors. The malting process involves soaking the grains in water and allowing them to germinate, and then drying the partially germinated grain in a kiln.

Malting is essential to produce enzymes that later converts the starches into fermentable sugars. The same grain can produce malts of different colors by controlling the roasting times and temperatures. Today, you can also find gluten-free beer by substituting gluten-containing grains with sorghum.

Water

Great water makes for great beer. 90-95% of the drink though is water. It is involved in every step of the brewing process and it takes roughly seven gallons of water to produce one gallon of beer. Although it doesn’t bring much to the flavor, its mineral content largely affects the quality and type of beer produced.

The ‘hardness’ of water depends on its mineral content. Hard water refers to water with relative quantities of dissolved minerals such as Calcium and Magnesium; Soft water is usually treated and only contains sodium ions.

As different regions have varying mineral contents in their water, different brews can be identifiable by regional characteristics. For example, Guinness originates from the Irish. Regional geology accords that Dublin’s hard water is suitable for making stout.

The existence of Gypsum in the waters of Burton, England, makes it suitable to produce pale ale. Different minerals contained in water have different uses. Calcium helps promote flavor and clarity. Sulphates emphasize bitterness, making the beer drier and crisper. Magnesium is an important co-factor for Yeast activity.

Yeast

The fermentation process for beer is catalysed by Yeast as it transforms the starch source into the wort, a sugary liquid. Yeast is added into the wort (liquid from boiling malted grain), which then metabolizes the sugar extracted from grains to produce alcohol and carbon dioxide, ultimately producing beer. Besides fermenting beer, yeast also influences the character and flavor.

There are two types of yeasts used in beer production: Ale yeast (Saccharomyces cerevisiae) and lager yeast (Saccharomyces pastorianus). In the olden days before fermentation and yeast were understood, fermentation occurred naturally via airborne yeasts. Several styles, such as lambic beer, still use this method today. (see How to make a Yeast Starter)

Pure yeast cultures were introduced in 1883 by Danish biochemist Emil Christian Hansen and are now used as the main fermenting source worldwide. Ale yeast is added to the top of the wort at a higher temperature, and it yields more flavor. Lager yeast, on the other hand, is added to the bottom of the wort at low temperatures and usually takes a longer time. This produces “crispier’ beer.

Hops

By the 15th century, another ingredient was discovered that was a gamechanger in the beer industry. Hops, specifically the cone-shaped flower of the female hops plant, gained its popularity in the beer-making industry as the main flavoring ingredient.

Before this time period, other plants such as grains of paradise or a mixture of aromatic herbs and berries were used as flavoring.

Some companies such as the Scottish Heather Ales company and French Brasserie-Lancelot company are still using other plants as flavoring in their beers. Hops are added to the boiling stage of the brewing process and usually takes a long time (an hour) for it to release its bitter acid. The choice and timing of beer hops addition will determine the type of brew produced.

Hops bring out the classic bitterness of beer that balances the sweetness of malt, which is usually described as floral, spicy, citrusy, and piney. Hops also have an antibiotic effect that allows the yeast to thrive by minimizing other less desirable microorganisms.

The acidity of hops also allows it to act as a preservative, giving beer longer shelf life. Check the IBU level. You can know how much hops to use in a beer.

Varieties of Hops

In the past 50 years, hop-producing countries have developed at least 50 varieties around the world. Today, hops are developed to meet the demands of brewers for improved yields, resistance to diseases, and improved aroma, soft resin content, storage, and stability.

Although slightly different than each other, every variety contains soft resins, which are the acids that contribute to bitterness and aroma. Brewers generally use bitter or “kettle hops”, and aroma hops. Choosing the best hop variety for beer has been a debate among beer enthusiasts and how they impact the IBU scale of each beer since we could start measuring it.

However, it is quite subjective as it depends on each brewer’s preferred taste. Some brewers stress the importance of where the bitterness comes from, while others demand pleasant aroma specific hop variety. Nevertheless, harsh or mild perceived bitterness can also be associated with the number of alpha acid analogs in the brew.

Here’s an extensive Hops Chart showing all the differences.

The pros and cons of traditional aroma hops

Traditionally, mildly bitter European aroma hops such as Saazer, Tettnanger, and Goldings and Fuggle were preferred due to their pleasant aroma characteristics. However, the supply of these aroma hops has declined over the years due to its complexity is growing. Most commercial hop growers do not prefer it unless special prices are offered making it more feasible.

Aroma hops have lower yields due to the introduction of off-types by careless planting and lack of resistance. These yields are more susceptible to diseases such as downy mildew, powdery mildew, and Verticillium wilt, which further complicates the growing process.

Problems facing traditional aroma hops and ways to overcome

Hop breeders either select higher yielding clones by mass selection or by selective breeding. It helps produce hops with the desired aroma, giving improved yield potential and disease resistance.

A phenomenon called hybrid vigour is partly responsible for the higher-yielding properties in new hop varieties. For the traditional aroma hops, which are over 100 years old. However, hybrid vigour gradually declines over time, causing it to decrease in yield over the years.

Cutting hops vines at harvest also weakens the plants from growing during the following season, as compared to traditional hand-picking methods. Cutting the vines disrupts the food supply for the entire hops plant. Therefore, traditional hop varieties are more affected by modern machine harvesting techniques than new varieties.

Other factors affecting hop production

Hops are not very adaptable plants. The performance – in terms of quality and agronomics – is affected by geographic area, the season, and specific microclimates.

For example, the alpha-acids content in German Perle is 3 to 4% higher in Oregon than Bavaria, where the hop originates. Another example is the Cascade hop variety selected in Oregon.

When grown in Oregon, Cascade has more alpha than beta acids; when grown n the Yakima Valley of Washington, more beta and alpha acids were found. Total levels of alpha acids may fluctuate between seasons and locations, but alpha-acids compositions, as indicated by humulone and co-humulone components, face relatively little change.

Seeded Vs. Seedless Hops

Hops around the world are seedless as they are propagated by cuttings, without the presence of male plants. Growers prefer growing male hops as pollination stimulates the growth of the cone and adds weight in the form of seeds to increase overall yield by 25%. The perianth or seed coating is the maternal tissue, and it develops resin glands found on the cones.

This increases the total soft-resin production of seeded hops due to its larger cone size and additional glands on the seed coat. However, when measured as a percentage of weight, the alpha-acids content expressed is slightly lower due to the dilutive effect of larger cone size and higher yields.

Nevertheless, there are increasing industry demands for hops with lower seed content. Seeded hops pose a problem for traditional kettle brewing as the seeds are uncrushed, and little seed fat can be obtained from the intact hop seeds.

This also poses a problem for hop processors. Experienced taste panels seem to be able to detect differences in seeded and seedless hops.

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