All About Using Hops

Hop Usage & Utilization

  • What are Hops?
  • The Science of Hops
  • When to Use Hop in Your Beer

What Are Hops

Hop AnatomyCross-section_of_hop_cone.svg


IBU stands for International Bittering Unit but what does it mean?

“Bitter” vs. “Hoppy”

  • Uinta Hop Nosh IPA – 82 IBUs
  • Unita Detour DIPA – 95 IBUs
  • Unita Dubhe Imperial Black IPA – 109 IBUs
  • Pilsner Urquell – 40 IBUs
  • Sierra Nevada Pale Ale – 37 IBUs

The Science of Hops

  • Alpha Acids
    • humolone
    • cohumulone
    • adhumulone
  • Not bitter and not soluble in water
  • Alpha Acids are “isomerized” in boiling wort, becoming iso-alpha acids.
  • In addition to bittering, these acids are responsible for foam stability and bacteria inhibition.
  • Beta Acids: Do you care?
    • Beta acids do not isomerize, but will break down through oxidation, adding bittering compounds.
    • Beta acid oxidation can also contribute unwanted aromas.
  • So what is “utilization?”
    • The percentage of available alpha acids that are isomerized during the boil
    • Typically around 30%
    • Affected by boil vigor, duration of boil, wort pH, wort density, kettle geometry, etc.
    • Don’t forget, our water boils at a lower temperature here!
  • Does the percentage breakdown of various alpha acids matter?
    • Cohumulone is the most efficient at utilization.
    • Cohumulone also drops out to a lesser degree during fermentation.
    • “Perception” of bitterness
  • Consider the SNPA vs. Pilsner Urquell example:
  • SNPA: Cascade Hops (37 IBUs)
    • 33-40% cohumulone
  • Pilsner Urquell: Saaz Hops (40 IBUs)
    • 23-28% cohumulone
  • One experiment, in which equal amounts of humulone and cohumulone were isolated and used to brew two different beers found the cohumulone beer to have 62% more IBUs!

So is it useful?

  • Provides a basis for standard measurement, allowing brewers to be consistent.
  • It’s not a measure of iso-alpha acid content alone
  • Based on an assumption that iso-alpha acids make up 5/7ths of the total bittering compounds in beer.
  • This was based on the fact that, many years ago, hops were much more oxidized than they are today.

So what to do?

  • Short of lab analysis, everything we do is an estimate.
  • When using low cohumulone hops, consider increasing hops up to ~40%
  • Also, IBUs drop by about 20% post-fermentation due to the drop in pH decreasing alpha acid solubility.

Bottom Line

  • IBU is just a measuring standard. Don’t focus on what the number is, instead focus on acheiving consistency over multiple brews, regardless of what that number is.

Hops: Flavor and Aroma

Essential Oils

Flavor and aroma are found in essential oils:

  • Myrcene
  • Humulene
  • Caryophellene
  • Farnesene

These oils are degraded by heat

Myrcene makes up the largest portion

Myrcene in hops:

  • Amarillo: 68-70% total oil (1.5-1.9ml/100g)
  • Hallertau: 35-44% total oil (0.6-1.5ml/100g)

Whirlpool/Hop Stand Additions

  • Account for temperature
    • Above ~180F, isomerization is still occurring, though at a lower rate. (5-15% utilization)
    • Below ~180F, isomerization is essentially shut down, but the lower temperature will require longer time to extract the oils.
    • (Andrew) typically uses 175F for 30 minutes

Hops: Dry Hopping

Dry Hopping

  • Extraction of essential oils via alcohol and pH.
  • Higher temperature will speed extraction
  • Fermenter geometry will affect contact time