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Science Friday: Beer Label 101

Sep 18, 2015 Comments (0) Science Friday: Beer Label 101


Do you ever wonder what all those abbreviations on your beer label mean? IBU, SG, and °Plato can seem like gibberish, but once you unravel the mystery it becomes quite simple and can give you a lot of information about the beer you’ve got in your hand.

Shannon, the one who does approximately a million tests on every batch of beer to make sure it's the highest quality possible (more like 30 something, but who's counting? Answer: she is.) walked us through a little Beer Label 101 so we can better understand what all of the numbers and words on the label tell us about the beer we love to drink.

Below are the definitions and explanations of how we measure some of the most common analytical beer label terms:

Specific Gravity (SG): Gravity describes the concentration of dissolved sugars in wort (Bonus term: wort, the malt-sugar solution that is boiled prior to fermentation. As we like to say in the business: brewers make wort, yeast makes beer.). There are a couple of different ways breweries measure and report the gravity.

On Ninkasi's labels, you'll see the Original Gravity (OG), which is the beginning gravity of the wort prior to fermentation and provides the brewer with an estimate of the alcohol potential of the beer. The higher the OG, the higher the alcohol. OG can range anywhere from 1.028 as in a lite American lager all the way to 1.120 as in an Eisbock or Russian Imerial Stout.

Another way you might see this listed is as the Final Gravity (FG), which is the gravity measured at the completion of fermentation. A beer with a higher FG will have some residual sugar leading to a sweet finishing beer, while a beer with a lower FG will have a dry finish. Different types of yeast can be used to achieve the desired amount of residual sugar in your beer. You may have noticed some IPAs are drier than others and this is most likely due to the type of yeast used.

°Plato (not the famous philosopher), is another measure of the fermentability of wort. °Plato is the percentage of sucrose in solution by weight. (Editor's note: that's a fancy way of saying "how dense the sugar is in the wort".) °Plato was derived empirically, so 100 grams of a 12 degree Plato wort contains 12 grams of mostly fermentable sugars.  It is commonly used in breweries as an alternative for SG and communicates the same information, just in a different number. A beer that is 10-13 °Plato will produce a beer that is about 4-6% Alcohol By Volume (ABV).

How we measure gravity: Gravity is traditionally read using a hydrometer, a bobbing instrument that floats in the wort to give a reading (editor's note: kind of like the buoy on top of a lobster trap, only there's no delicious shellfish waiting to get boiled, buttered, and scarfed up.). More sophisticated methods are also available to measure gravity; including a device with an oscillating U-tube (no you can’t watch cat videos with it). 

IBU: International Bitterness Units, usually referred to as simply "BU", is a measure of the bitterness of beer derived from the isomerization of alpha acids in hops (editor's note: "isomerization" means the chemical reaction that happens when the hops are added to boiling wort). When hops go in to this boiling wort, the hop resins are able to become utilized and dissolve into the wort. The ultilization of hop acids is dependent on several things, including length of the boil, the gravity of the wort, and amount of alpha acids in the hop variety.

IBUs can range from as little as 3, as in a Berliner Weisse, to greater than 100, as in an IPA or American Barleywine. Measured bitterness, however, is different than perceived bitterness. Although an American Barleywine has an IBU range close to that of an IPA, it will not taste as bitter because the malty sweetness provides a nice balance.

It is also important to realize that while IBU numbers can be useful for designing recipes, tasting the beer is the ultimate test! With the advent of dry-hopping, we are now able to add hop aroma and flavor while stabilizing the bitterness of beer. (Dry-hopping is the process of adding hops to beer at any point after the boiling of wort, but ideally it is done late in fermentation. The hop oils are then able to diffuse into the beer without adding extra bitterness.)

How we measure IBU: We measure IBU in the lab using a liquid-liquid extraction method where the alpha acids from the beer are transferred into another liquid phase. We then measure the absorbance using a spectrophotometer and with a little simple math we get an IBU number.

Alcohol by Volume (ABV): The higher the number, the higher the amount of alcohol in the beer (that's science, folks.)

How we measure ABV: We measure ABV in the lab with an Alcolyzer machine. The Beer Alcolyzer makes a direct measurement of the alcohol content of beer using a patent protected procedure employing specific NIR spectroscopy. By using only specific wavelengths, the influence of the beer’s other components is avoided, ensuring accurate alcohol measurement.

Warning!!!: If you have read to the end of this post then you may be considered a beer nerd in some circles. Feel free to drop a little beer knowledge at the water cooler.

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