GNBrews

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What mechanism is responsible for keeping the aroma of a late hop addition in the wort? Are the aromatic oils really that soluble that they can be extracted into the wort with a 2-5 min contact time? I'm looking to increase my aroma addition efficiency, and would like to know what is going on in those few minutes.

Thanks!

carnevoodoo

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The brew wiki has some information on it.

Hop chemistry - Home Brewing Wiki

"When added to boiling wort, alpha acids go into solution almost immediately. However, the bitterness they impart to beer appears only gradually, as the alpha acids are slowly isomerized in the boil to form isomerized alpha acids or iso-alpha acids. This is why bittering hop additions are normally done at the beginning of a boil of 60 minutes or longer."

carnevoodoo

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Also:

"While alpha acids contribute most of the bitterness to beer, most of the hop flavor and aroma is contributed by volatile essential oils. Hop producers generally indicate the total percentage of essential oils by weight in a given hop, and sometimes identify specific oils by percentage of total oil.

Because hop oils are highly volatile, traditionally the aroma and flavor characteristics of hops were obtained by late hop additions or dry hopping, allowing the oils to be absorbed into the wort but not leaving them in the boil long enough to boil off."