A hop stand is something JK has been doing since he first met Luke Nicholas of Epic Brewing in New Zealand. Luke has been making and still makes some of the best beers in New Zealand for one very good reason, he went to the US and learnt from the top brewers over there. JK remembers it was one fairly boozy night in 2008 at the Malthouse in Wellington, he was drinking either Epic Armageddon or Epic Mayhem and was amazed at the aroma and at the flavour… “how could I brew beer like this, everything I was reading told me that I was doing things right…I should have better beer?” He thought. So he asked Luke who very kindly divulged his knowledge on the subject.
It turns out that what the Americans and Luke were doing was loading their hop additions at the end of the boil ignoring traditional brewing techniques. What this means is that you don’t work out your IBUs and your boil hop amounts first, you do that last. The first thing you do is work out how many grams per litre (g/L) aroma and flavour hops the beer requires. This can be anywhere between 2-10 g/L or more. A nice starting point for low gravity beers is 5 g/L from this you can work out what the bitterness contribution to the beer is.
Alpha acids will continue to isomerise after flameout until the temperature of the wort reaches about 79°C. Homebrewers trying to calculate a beer’s IBUs will need to ‘guesstimate’ how much isomerisation is occurring. The closer the wort is to 100°C the higher the alpha acid isomerisation rate. To do this, we can look to professional brewers for some guidelines. Ultimately, however, the thermal capacity of a professional 60bbl whirlpool vessel is quite different than 20 L of homebrew! So the comparisons can only be rough guidelines at best.
From JK’s own experience with extended hop stands in 20 L batches to 10bbl, a 3-5% utilisation rate for whirlpool hops seems reasonable.
|Use this table to work our your hop utilisation rate for your whirlpool hops|
So instead of the traditional additions at 30, 15, 7, 5 and 1 minutes all the hops are added at the end of the boil, what JK calls a hop stand.
This allows the hops added at flameout to release their essential oils into the wort, while minimising the vaporisation of these essential oils, adding a kick of hop flavour and aroma as well as what can best be described as a smooth bitterness.
At wort boiling temperatures, ALL hop essential oils have surpassed their flashpoints, so a vigorous boil will drive them off fairly quickly. The best way to think about the driving off process is in terms of half-lives. The lower the flashpoint, the faster the oil vaporises and the faster the half-life. The longer the hops are boiled and the lower the flashpoint, the less the essential oil will impact the beer. In effect, hop stand hopping removes the rolling boil (for the hop stand hops), lowering the temperature of the wort and therefore reducing the vaporisation rate of the essential oils, allowing the essential oils to really “soak in” to the wort. The specifics of the “soak in” process is still very much a grey area but the idea is that essential oils will be retained in the beer longer and enhance the hop flavour and aroma of the finished beer.
A hop stand is simply allowing the boiled wort an extended contact period with the flameout hops prior to chilling the wort. Professional brewers typically create a whirlpool either in their kettle or in a separate whirlpool vessel with the hot wort and the ensuing vortex creates a cone shaped pile in the centre of the vessel made up of the unwanted trub and left over hop material. Whether on purpose or inadvertently, pro brewers were giving their flameout hops extended contact time with the wort. This allows the hops added at flameout a period to release their essential oils into the wort, while minimising the vaporisation of these essential oils. In essence, adding a kick of hop flavour and aroma while also adding what can best be described as a smooth bitterness. In short, whirlpool hopping can add significantly to the hop flavour and aroma of beer.
The second factor to consider is the length of your hop stand. There are no right or wrong answers, but anywhere from 10 minutes to 90 minutes can be employed. JK worries a little about leaving his hops to stand for too long, he doesn’t want DMS reforming so as a rule he hop stands for 30 minutes, giving the hops a good stir after 10 minutes.
Try it when you’re next brewing and see the impact it has on your beer.
Great explanation! This will make the bitterness hops added during the boil stay longer in the wort. Will this also bring added bitterness???
Yes, that is correct