Hops have been called the spice of beer, and the analogy is apt: They have flavor and aroma qualities that can evoke tropical fruit just as easily as they can a pine forest. One hallmark of a skilled brewer is his or ability to add just the right hops at just the right times to achieve the desired profile.
It’s only somewhat recently, however, that hops have become as prized for their organoleptic properties (aspects we can experience via the senses) as they are for their bittering potential. Indeed, breeding programs historically aimed to improve alpha-acid levels while keeping cultivars classically “hoppy,” which usually meant keeping the herbal and floral aromatics so prized in noble varieties.
Boiling hops in water or wort transforms alpha acids into iso-alpha acids, which deliver bitterness. And the degree to which this happens is known as hops utilization. Hops utilization is the fraction of the available alpha acids that both (1) transform into isomerized forms and (2) remain in the finished beer, so the number is always less than 100 percent. In most cases it’s closer to 25 percent. An incredible number of variables influence this number, and the following tend to enhance utilization:
- Hotter water
- More vigorous boiling
- Longer boil time
- Larger boil volume
- Higher wort pH
- Lower wort gravity
- Longer post-boil chill times
- Smaller amounts of trub material