Hops

[benno1973]

In two litres of what?

Wort = good. Water = bad.

Not trying to start a Bum fight.... what is the theory behind it?

From Mr Wizard (BYO mag):

When hops are added to wort and boiled the pH is around 5.2 and there is protein present to precipitate much of the polyphenols extracted from the hop leaf. Boiling time is important and most beers that have hop aroma use late additions. During the boil, hop acids undergo numerous chemical changes and the resultant mix has a profound influence on beer bitterness and the quality of bitterness. When the pH of wort boiling is increased by adding alkaline buffers, hop utilization increases but bitterness is reportedly unpleasant. If you boiled hops in water as opposed to wort, the pH would be higher and the flavor would lack.