probablement ? tu peux développer ?Jinac a écrit :Et les aacides alpha ne sont probablement pas les seuls composés qui donne l'amertume...
Sinon, y'a des choses intéréssantes sur ce lien : http://beersmith.com/blog/2013/01/21/la ... r-brewing/
Bitterness comes from the alpha acids in hops (in chemistry terms these are the humulones: humulone, cohumulone, adhumulone). During the boil, these alpha acids undergo a chemical reaction called isomerization which transforms them into bitter compounds – the traditional bitterness we taste in beer.
et çà :
Essential Hop Oils
In addition to alpha acids in your bittering hop addition, there are four main hop oils that can add flavor late in the brewing process – each of which boils off at a different boiling point. Most also rapidly oxidize when exposed to air:
Myrcene – (147 F/63.9 C boil point) – The largest of the hop oils, making up 40-60% of the hop oil content in many American varieties (Cascade has 50-60%), though most noble hops are low in myrcene (Saaz: 5-13%). Mercene boils off readily, and can even volatilize in a high temperature steep (147F), so you will lose it if you boil it. It has a herbal note that can be described as green, balsamic, hoppy in small quantities. It also has a slight piney/citrus flavor. As a result of its low boiling point, it is present in much higher quantities in dry hopped or steep-hopped beers. It tends to provide a “green hop” or fresh hop aroma when used in dry hopping.
Humulene – (210F/99C) – Humulene is the traditional noble hop oil, providing a strong herbal component most people associate with noble hops. Humulene is actually widely used in the perfume industry for its herbal characteristic. Over long boils, it also tends to produce a slightly spicy flavor – such as that from Saaz hops in light lagers or Nugget. Because it boils just below the boiling point of water, it usually provides its best characteristics as either a late boil addition or post-boil addition. Humulene will not survive a long boil, and is also prone to oxidize.
Caryophellene – (262F/129C) – Caryophellene is a counterpoint to humulene – and provides a spicy, woody, earthy and even citrusy flavor. Clove and pepper contain this oil in significant quantities. While not a significant in noble hops, Caryophellene is a major aroma component in many traditional English hops such as Goldings and Northdown as well as many US hops such as Mount Hood. In beer it contributes a strong dry wood, pepper and earthy spice flavor. It may even add a citrus finish. Many hops are rated by their Humulene to Caryophellene ratio with noble hops having a high ratio of 3:1 or more. Caryophellene oxidizes rapidly, so fresh hops must be used and are often added late to preserve the flavor.
Farnesene – (203-257F/95-125C) – Found in the coating of apples and other fruits, it provides the “green apple” flavor as well as flowery, citrusy, woody and at the extreme end musty, woody or vegetative. Farnesene is the smallest of the hop oils – typically less than 1% of the hop oil content, but it can be higher in many noble varieties. Again because it oxidizes rapidly it is best preserved as a late or post boil hop addition.
