Whirlpooling

By Mike Retzlaff

The whirlpool method of trub and hop separation from boiled wort started commercially around 1960 by Molson in Canada.  It is based on a phenomenon which is counter-intuitive.  The initial purpose of whirlpooling was to separate wort from hops and trub.  There are other methods to accomplish this important task.  One that has been used for hundreds of years is the Hop Back or Hop Jack.  It is basically a lauter tun in which the kettle is drained after boiling the wort.  The hop back has a layer of hops strewn across the bottom to add hop aroma & flavor and also to help filter out kettle hops and trub.  With the relatively massive amount of wort in a commercial brewery and the propensity of oxidation of hot wort during transfer, whirlpooling is decidedly a better option.   

It isn’t known when the “Tea Leaf Paradox” was first observed.  However, James Thomson offered the first correct physical explanation back in 1857.  Einstein solved it in a paper he wrote in which he explained the erosion in the bends of river banks in addition to the curious deposits in a teacup.

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Whirlpool trivia: (by Ashton Lewis – Siebel Institute & Springfield Brewing)

Some tea drinkers who use loose tea and no tea ball separate the tea leaves by stirring their tea after the leaves sink to the bottom of the cup to cause the leaves to migrate to the center of the cup.  Albert Einstein thought this phenomenon was pretty nifty.  He developed a general explanation, called the Teacup Effect, of why pressure changes cause solids to migrate to the center instead of to the perimeter, where it seems like they should migrate.  His explanation came in 1926.  Molson Breweries in Canada is credited with first using the whirlpool in commercial brewing.

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Other techniques are piggy-backed onto the whirlpool such as late hop additions to add flavor and aroma without a big IBU contribution.  Some commercial brewers are now chilling the boiled wort to 170o to 180o F to bypass hop isomerization thereby limiting excessive bitterness.

I had a conversation with a professional brewer (over 30 years with Coors) who told me of several instances of other brewers bragging about the great deal they got on a whirlpool tank.  Upon inspection, he found that these units apparently had been built for the South American or Australian trade as the whirlpool jets were oriented to provide the wrong rotation of flow for the northern hemisphere.  I suspect they worked okay anyway; after all, draining these tanks isn’t quite like flushing a toilet.