[yso191]

I am writing to correct an error that I have repeated many times.  The error goes like this:  the boiling point of hop oils vary, but it is always far less than that of water.  So if one doesn’t want to lose hop oils, add your flavor and aroma charge at, for example, 170*.  This is not correct.  The boiling point of a solution is reduced a bit by the addition of substances that have a lower boiling point than that of water, but the whole solution boils or none of it does.  Here is a link that goes more in depth on the subject: http://www.kelleybarts.com/PhotoXfer/ReadMeFirst/MagicBoilingMyth.html

[klickitat jim]

Steve, I've often wondered if people overly fear "boil point" of hop oils. It seems like the thought is that if hop oils "boil" at X° that as soon as you hit X° they are gone... instantly. But why doesn't that happen with other substances, like water for instance. Every time I bring water to a boil it seems to not instantly evaporate. While I can't look in the boil kettle and "see" hop oils, by smell and taste it sure seems like a lot of hop oils are staying in there, even though they were at their boil point.

Doesn't time at boil point also play into it?

[Robert]

And don't you need to take into account the rate at which the hop oils oxidize to soluble form, or otherwise become bound to other substances, reducing their volatility? 

[erockrph]

All the major hop oils that I've looked up have boiling points that are greater (and often much greater) than 100C. Type something like "Myrcene" or "Linalool" into Google, and you'll see a summary of some of the basic chemical properties from Wikipedia listed in the sidebar. They are not likely to be boiling off before the water in the wort does.

[Robert]

And again, remeber that none of the hydrocarbons in hops survives in wort, let alone beer, only their oxidation products.  Just considering the properties of the oils themselves misses the point.

[erockrph]

And again, remeber that none of the hydrocarbons in hops survives in wort, let alone beer, only their oxidation products.  Just considering the properties of the oils themselves misses the point.

Interesting, every paper I've ever read refers to the amount of the terpenes themselves (myrcene, cintronellol, linalool, etc,) when assaying beer. Do you have a source for this?

FWIW, if they can detect myrcene and linalool in 1978 in a lightly-hopped American Lager, I'm reasonably sure that a modern craft beer will have them present as well.

http://jfoodprotection.org/doi/pdf/10.4315/0362-028X-41.9.722?code=fopr-site

[Robert]

No, just recall everything I've read refers to the flavors and aromas being contributed by oxidation products and stating that myrcene, farnesene, etc themselves are never found in beer.  Been years, guess I'll have to go find everything I can again.  Could well be wrong.

EDIT in fact IIRC isn't linalool (and geraniol) in beer from myrcene oxidation products? Have to go do some looking.

Further EDIT

Some good info in Briggs, et al Brewing Science and Practice ch 8; good textbook in general.  (Link to a link to pdf in Big Monk's sticky on All Grain board)