Hops (Humulus lupulus) are used to:

1. Add bitterness to the beer via the alpha acids that isomerize during the boil → IBU (International Bitterness Unit)

2. Add aroma to the beer via the essential oils and volatile compounds

3. Preserve the beer, thanks to the antibacterial properties of the alpha and beta acids

Types of hops:

• Noble hops: Hallertau, Tettnang, Spalt, Saaz → mild bitterness, herbal/floral aromas

• American hops: Cascade, Centennial, Amarillo → fruity, citrus, resinous aromas

• Aromatic/modern hops: added late or in dry hopping to maximize the aromas

The hopping technique influences the final profile:

• Early hopping (long boil) → dominant bitterness

• Late hopping (end of boil) → aromas and flavors

• Dry hopping (added during fermentation) → intense aromas without bitterness