On Food and Cooking

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