To all you chemists out there.....
What do hops contribute to the wort in terms of WEIGHT.
By this I mean the oils that are extracted into solution during the boil, since the hops dont end up in the final product do to filtration.
other pertinant information...if needed. 5bbl boil volume, average gravity of wort (12-15P) and moderate hopping rates, for a mild pale ale.
The actual hop bitterness portion is equivalent to ppm, i.e. a beer with an IBU of 30 contains 30ppm by weight of alpha acids. However I am not sure what weight of hop oils are typically contained in beer. Obviously this will vary according to the hop type, how long you boil for, timing of hop additions, whether you dry hop etc etc. There will also be small quantities of other hp resins, tannins, salts, proteins and sugars. Again, I have never seen a value quoted, though I expect someone in one of the research establishments has bothered at some stage.
Quite frankly, from a practical point of view, hops comprise a negligible proportion of the final beer, even in some of the bery highly hopped beers.
There is a hop addition calculator on this web site, another on ProMash, and others around I am sure. The hop utilisation depends upon kettle design and operation (boil vigour), wort strength and hop addition time. Since I am used to rather larger plant than probably most visitors to this site, one of the micro brewers is probably better placed to give an indication of their utilisation. As a starting point, I would aim for 30 to 35 %, but....
Hop bitterness is measured in parts per million and are called IBU, International Bitterness Unit. That is the soluable portion of bitterness in beer. The hop material is removed from the wort. Once you are talking in parts per million you are basicly talking about no weight hardly at all in beer. 30 IBU is 0.003% by weight. Essential oils from hops are even smaller quantities and some can be measured in parts per billion. Ignoring the water content, beer is mostly residual unfermented extract, alcohol, protein, and trace amounts of compounds. Many of these trace compounds can have a significant impact upon flavor.