Measuring Beer - A Lesson In Hops and Color

Hops Who would have thought that something as subjective as 'bitterness' could be measured and quantified? But thanks to the ingenuity of brew chemists, that's just what has been done. 'Brew chemist'. How's that for a career idea to warm the heart of every college sophomore.

Hops are cone-like flowers which grow on vines in temperate regions of Europe and North America. At the base of the petals are lupulin glands that contain the oils that contribute to the brewer's art.

Historically, hops were used more as a preservative than a flavoring agent. With modern brewing technology, that's no longer necessary, but the flavoring aspect is still extremely important.

Bypassing a lot of complicated chemistry and math, hops are bitterness rated by a measurement called IBU, or International Bitterness Units. An important component of IBUs is a factor called AAU, or Alpha Acid Units. It's the alpha acids in hops that provides most of the bittering effect that helps balance the sweetness from the malt sugar used. Beta acids form only about 10% of the total.

When added at the beginning of the boiling process that is the initial phase of fermentation, the hops contribute more IBU than if added later. Knowing the IBU rating for a sample of hops allows home brewers to control, to some degree, the bitterness level of their output.

Calculations are now more or less standardized and ratings range from less than five for a weakly hopped brew, while an India pale ale or Barleywine can reach as high as 50 IBUs or more.

Though the numbers are standardized, the results are not. The largest factor that affects the final outcome is the boiling time. Boiling causes the hop oils to break down and combine with the wort (the malt sugar liquid used for fermentation), which partly determines the amount of bitterness of the final brew.

The second largest factor is the specific gravity (SG) of the wort. Hop utilization decreases as the SG of the wort rises, since the higher concentration of sugars - and thus the greater SG - leads to fewer alpha acids dissolving into the mixture.

Measures of IBUs and tables of the quantity of hops to add are typically on the package or in the brew kit sold by your vendor.

Most beers are made largely from pale malt and a large percentage of specialty brewers prefer the two-row barley malt variety. But other malts are sometimes used to control the color and tailor the taste of the final product.

Like coffee beans, malt is roasted to caramelize the sugars and increase sweetness and produce attractive darker colors. Also like coffee beans, roasts come in all degrees. Some produce only a slightly tanning effect, while others nearly burn the malt giving a very dark brown. Roasted malts are typically added in graded amounts to produce just the degree of browning desired, from amber to chocolate.

Malts, like hops, have now a standard rating, in this case the so-called 'Lovibond' scale. Using the Lovibond number can help a home brewer tailor his color, just as IBUs are useful for honing bitterness.

For example, ten pounds (4.5 kg) of 40L malt would produce the same color as 40 pounds (18.2 kg) of 10L malt. The normal range is from as low as about two for very light American beers, to around 40 for a good British stout.

Again, the package or home brew kit should provide the number, which you can use as a starting point for creating your own unique brew.