Applications of natural ingredients in alcoholic drinks - Natural Food Additives, Ingredients and Flavourings - page 361

aroma extract dilution analysis (AEDA) to compare the beer aromas derived from
Challenger and Saaz hop pellets. State-of-the-art analytical techniques have also
been used more recently to:
• Study the decrease and increase of several key hop derived terpenoids during
boiling (Kishimoto et al. 2005).
• Study the odour-active compounds in the spicy fraction of hop essential oil
from four different varieties (Eyres et al. 2007).
• Compare odour-active compounds in unhopped wort and beers hopped with
different hop varieties (Kishimoto et al. 2006).
• Identify and characterise new volatile thiols derived from hops (Takoi et al.
2009) ( Fig. 16.2 ).

During the harsh boiling and subsequent fermentation stages of beer production,
large quantities of aroma compounds are lost through evaporation and by
numerous chemical transformations. However, brewery controls using a particular
hop variety should ensure that the hop character of the fi nished beer remains
reasonably constant from batch to batch.
Many beers are produced using a single traditional hop variety, but others are
brewed with two or more varieties, often for a particular aroma/fl avour impact
character. It is quite common for high α -acid hops to be added at the start of
boiling, with aroma hops being added toward the end of boiling and post boiling,
or for aroma hop and dual purpose hops to be added at the start and toward the end
of the boiling. The brewery's aim is to achieve an acceptable bitterness and to
preserve the attractive aroma. This aim can also be fulfi lled by the use of isomerised

￿ ￿ ￿ ￿ ￿

Fig. 16.2 Odorous thiols found in Nelson Sauvin (New Zealand) hops. From Takoi et al.

(2009). *New.