The Case Against Whirlpooling

 

Whirlpool port on a homebrew sized boil kettleWhirlpool port on a homebrew sized boil kettle

 

Introduction

We get asked quite often why we don't whirlpool or recommend whirlpooling on homebrew sized setups, so we figured a guide was in order to explain the pros and cons as well as answer the most common questions.

First, let's define the term 'whirlpooling' as there is much confusion surrounding it:

Whirlpooling is a method used to separate debris (mostly hop pellets and trub) from wort after the boil. In large commercial setups the wort is usually pumped into a separate whirlpool vessel while at the smaller homebrew level it's usually pumped back into the boil kettle. Both are done at rapid velocity with the wort entering at an angle to follow the outer wall of the vessel, which causes the wort to start spinning like a whirlpool. Some homebrewers on very small setups attempt to replicate this by simply stirring quickly. The spinning wort is then allowed to settle which causes the hops and trub to form a cone in the center of the vessel. The wort is then carefully drained from the edge, leaving the debris behind.

Whirlpooling is not to be confused with steeping hops or hop stands (both of which we do regularly in many of our recipes). Whirlpooling has nothing to do with adding hops.

 

What are the benefits to whirlpooling?

There is one (and only one) benefit to whirlpooling: It keeps hops and trub out of the fermenter.

 

What are the downsides to whirlpooling?

  • Adds time to the brew day as wort must first be circulated quickly and then allowed to settle into a cone. Expect an additional ~30 minutes on typical homebrew sized setups.
  • The hops continue to steep in near boiling wort during the extended whirlpool and settling period, converting late addition hop oil flavours and aromas to bitterness. That may not be what you want, but you have no choice given that you must allow the hops and trub to settle in a cone before draining. (For some of our beers we like to start chilling immediately after the end of boil hops are added). 
  • May introduce hot side aeration (HSA). While HSA is a controversial subject that brewers do not agree on, we try and limit it regardless. Oxygen is not desired in hot wort because it can combine with lipids, melanoidins, tannins, and other elements to produce undesirable compounds which may stay in the wort through fermentation and end up in the finished beer and promote staling. Staling is a complex set of organic chemical changes that occur in beer over time, transforming its flavour and causing it to diverge from the desired and expected flavour and appearance.
  • May require extra equipment (whirlpool inlet, pump, etc.).

 

Commercial brewers whirlpool so isn't that better?

Not necessarily. There are different ways to get clear wort without having to whirlpool and allow the required settling time.

We find that many homebrewers think whirlpooling is the best option because that's what commercial brewers do, and therefore model their equipment and processes after commercial breweries without realizing why. Because of the large scale of commercial operations, commercial brewers operate under constraints that most homebrewers (or even small scale commercial brewers) don't have.

One of the steps larger commercial operations will employ is this whirlpool to help collect debris in the center of the kettle to minimize the debris downstream in their processes. Often a completely separate vessel is used with a whirlpool (tangential) inlet such that the boiling wort is pumped in at high speed and naturally whirlpools.

Commercial whirlpool vesselCommercial whirlpool vessel. Image (c) portlandkettleworks.com

Hob/trub cone after whirlpooling on a large commercial setupHop / trub cone after whirlpooling on a large commercial setup. Image (c) bitesnbrews.com

Homebrewers of course also want to minimize debris, but given the differences in scale more options become available for homebrewers.

Additionally, while a whirlpool can work in principle on a homebrew scale, we've seldom seen one that works so well as to actually "pile" debris in the center of the kettle as you need significant flow. Typically, homebrewers use small pumps that don't generate the flow rate necessary to really spin the wort. You almost need a vortex to really get trub accumulation and leave clean space around the edges of the kettle for the dip tube.

 

I thought you had to whirlpool to extract hop oil?

No. The amount of hop oil extracted is a function of contact time and temperature (longer and hotter has higher extraction). The hops do not need to be in motion. Steeping is fine.

We feel that much of this confusion comes from the fact that large scale professional brewers that have to whirlpool have been calling hops added during this last step as 'whirlpool' hops. New brewers may have misinterpreted that to mean that the hops must be whirlpooled (stirred) which isn't true.

 

If you don't whirlpool, how do you separate wort from hops / trub?

We use a filter called the Hop Stopper as it gives us the benefit of being able to start draining immediately after the boil without the need for a whirlpool and settling time.

This helps better lock in those bright late addition hop flavours and aromas for beers that need it the most (IPAs / NEIPAs, and so forth) by minimizing the conversion of hop oil flavours and aromas to bitterness. We will still steep hops post boil for certain beers (for example, Electric Hop Candy) using what's called a 'hop stand', but usually at lower temperatures in order to limit the isomerization of alpha acids into bitterness.

Hop Stopper installed in a boil kettleHop Stopper installed in a boil kettle

Hops added at the end of the boil will impart larger amounts of aroma if the wort is cooled quickly and immediately after the hop addition. During our boil kettle draining process, much of the finishing hops also settle on the Hop Stopper screen while hot wort flows through it, much like a hop back (such as the Blichmann HopRocket). The wort is then immediately chilled in-line to pitching temps, locking in the oils and flavours / aroma. We do have a hop back, but other than some initial experimentation many years ago, it now sits on the shelf unused.

Our lonely hop back sits unused

If clean wort and maximizing hop flavour and aroma is the goal, an effective screen type filter like the Hop Stopper is very simple to implement on a homebrew scale and requires no extra processes or equipment other than the screen itself.

 

So why don't commercial brewers use hop screens?

On the commercial level a screen type filter cannot be used as it just isn't practical. The home brewer has a distinct advantage because of the smaller batch size. On a homebrew scale, a hop screen is a very practical way to get all the clean wort benefits of the whirlpool without the extra time.

 

What's the fastest way to chill?

When we designed our home brewery, time was important to us so our processes were designed to be as time efficient as possible without affecting the quality of the product or system flexibility.

Luckily the fastest chilling also happens to produce the best product for us. In-line chilling is the fastest chilling method, period, so that's what we use. While we have seen the quick chill times on some of the high performance immersion chillers available, they don't take into account the total amount of time for the overall process which is chilling plus draining (they only ever include the chilling time, never the transfer time to the fermenter).

In-line chilling combines draining and chilling into a single step. Turn off the kettle, and a few minutes later you have wort in the fermenter with all of the hop flavours and aromas are locked in. This just isn't possible with immersion chillers. In addition, a well designed in-line chiller is more efficient and will chill the same amount of wort faster, and use less water than an immersion chiller.

For more information see our Wort Chiller guide.

 

Doesn't in-line chilling put the cold break in the fermenter? 

Yes. In-line chilling puts the cold break in the fermenter, while immersion chillers leave it in the kettle.

We've tasted world class beers using both processes. We've also tried fermenting with and without cold break (by allowing the cold break to settle out in the fermenter and then racking off) in sparkling clear light tasting lagers as well as cloudy IPAs. All were fantastic, so today we always ferment with cold break in. It can actually be beneficial and help with fermentation as it contains essential fatty acids.

Cold break is different for every beer as the composition is directly related to the ingredients and mash schedule used. Try it both ways with your favourite recipes to see if you have a preference (we don't). We find building a properly sized yeast starter prior to fermentation, proper aeration / oxygenation, and maintaining optimum fermentation temps are miles more important than whether or not you are fermenting with cold break or not. In fact, if you aren't doing those three things, very little of what you do upstream will matter much at all.

 

Should recipes be altered based on whether a whirlpool is used or not? 

Yes. Hop additions in recipes should be tailored to match the post boil brewing process that is used simply because the longer hops are steeped at high temperatures, the more hop oils that are converted bitterness.

For example, a commercial brewer with a very large setup may only add hops at 0 minutes (end of boil) because they know that their whirlpool will take 30 minutes. Given the volume of wort involved in large commercial setups, the temperature will stay close to boiling due to the thermal mass available. They are therefore effectively boiling their hops for an additional 30 minutes. It's not uncommon to take a recipe from a large commercial scale setup and have to move all hop additions backwards 30 minutes to get similar results on a homebrew scale.

All of our recipes are tailored for our brewing process which uses a fast in-line chilling method as described in our Brew Day Step by Step guide.

 

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