One of the best ways to bring more hop flavor and aroma to your homebrew is adding hops at flameout and allowing extended contact time with the hot wort before chilling. This process, which is popular among craft brewers creating hoppy beers and is being used more in recent years among homebrewers, is known as whirlpool hopping, or performing a hop stand.
Whirlpool hopping gets the best traits of adding hops in the fleeting minutes of the boil and of dry hopping as the hot wort (below boiling temperatures) allows for the contribution of essential oils that are not released in dry hopping temperatures, while also minimizing the vaporization of these essential oils as will happen in boiling temperatures. This process will add some bitterness to the beer, as alpha acids isomerize at temperatures above 175 °F (79 °C). However, the isomerization rate will be lower than in boiling temperatures at or above 212 °F (100 °C), and is generally considered a smoother bitterness than early boil additions. For recipes in Brew Your Own, we calculate a 10% conversion of alpha acids to iso-alpha acids for flameout hops that will be put through a hop stand prior to cooling.
Hop stands are usually performed anywhere from 10 to 90 minutes, depending on the results you are looking for. A longer stand will extract more bitterness (assuming the wort temperature stays above 175 °F/79 °C). For IPAs, a 90-minute stand may make sense, whereas a style in which you are just looking for subtle hop aroma and little to no contributed bitterness, a
15-minute hop stand may do the trick.
As the temperature of your post-boil wort changes, so will the affect it has on your hops. Right off the burner, in a temperature range of 190–212 °F (88–100 °C), essential oils will most easily solubilize in the wort and a greater bitterness will be contributed. Once the wort temperature cools into a sub-isomerization range from 160–170 °F (71–77 °C) bitterness will no longer be contributed from the hops, but the essential oils will be soaked up with little vaporization. When the temperature gets even cooler the vaporization of essential oils will lower even more, but the time required to extract these oils will also increase. The easiest way to perform a hop stand is to allow your wort to cool for as long as you want your hop stand to last (before cooling it to fermentation temperatures with a wort chiller or in an ice bath) but if you are specifically looking for a consistent hop stand temperature around 200 °F (93 °C) to add bitterness you can keep your kettle on low heat. Alternatively, if you want the cooler hop stand, you could use your chiller to bring the wort down to that temperature and then perform your hop stand.
While they are most often considered when brewing hop-forward beer styles, hop stands can be a tool in the homebrewer’s repertoire for many styles. For beers in which bitterness is low but hop aroma is desired, you can forego most of the bitterness hop additions you would traditionally add and instead pick up the desired IBUs from the hop stand. Craft brewers who perform hop stands generally add the hops either in the kettle or a separate whirlpool vessel and create a wort vortex immediately following the boil. This whirlpool vortex is not necessary for homebrewers, however it can be achieved if you use a pump to keep it circulating. Otherwise, after adding the hops, give your wort a good swirl and put the cover on the kettle and let the hops do their thing.
Just like all other hop additions, performing a hop stand should not prevent you from also dry hopping or adding hops near the end of the boil. Both of these additions have their benefits too, so think about what you are trying to achieve and consider each separately, or combined.