digestive enzymes, weakens cell walls, and begins the process of converting starch into fermentable sugars The shading indicates the progress of cell-wall weakening and starch digestion Malting is stopped when the growing shoot just reaches the tip of the kernel Bitterness and Aroma Hops provide two different elements: bitterness from phenolic “alpha acids” in their resins, and aroma from their essential oil Some hop varieties contribute a dependable level of bitterness, while others are prized for their aroma The important bittering compounds are the alpha acids humulone and lupulone In their native form they’re not very soluble in water, but prolonged boiling transforms them into soluble structures that flavor the beer effectively (Brewers sometimes use hop extracts that have been pretreated to produce the more soluble alpha acids.) Because boiling evaporates away many of the volatile aroma compounds, another dose of hops is sometimes added to the brew after the boiling, specifically to add aroma The aroma of ordinary hops is characterized by the terpene myrcene, which is also found in bay leaf and verbena, and is woody and resinous “Noble” hop varieties are dominated by humulene, which is more delicate, and often contain pine and citrus notes from other terpenes (pinene, limonene, citral) The American variety “Cascades” has a distinctive floweriness (due to linalool and geraniol) Brewing Beer The brewing of beer takes place in several stages Mashing: ground barley malt is soaked in hot water This revives the barley enzymes, which break starch into sugar chains and sugars, and protein into amino ... myrcene, which is also found in bay leaf and verbena, and is woody and resinous “Noble” hop varieties are dominated by humulene, which is more delicate, and often contain pine and citrus notes from other terpenes (pinene, limonene, citral)...compounds, another dose of hops is sometimes added to the brew after the boiling, specifically to add aroma The aroma of ordinary hops is characterized by the terpene myrcene, which is also found in bay leaf and. .. and citrus notes from other terpenes (pinene, limonene, citral) The American variety “Cascades” has a distinctive floweriness (due to linalool and geraniol) Brewing Beer The brewing of beer takes place in several stages