Hop Spiders

The name hop spider is peculiar to me since these devices don’t resemble any spider I have ever seen! But they are effective in retaining hops and minimizing carry-over of hop debris after the boil. They can also reduce wort loss for brewers who stop wort transfer when debris is seen in the line to the fermenter. So in general, I think hop spiders make sense and are a very useful tool form the homebrewer.

Your question is primarily about hop utilization. The primary factors that influence hop utilization are boil time, wort density, and wort pH. Secondary variables include hop type (pellet versus cone), kettle geometry, kettle size, and contact between hops and wort. The latter is the variable of concern with hop spiders. If hops are not able to fully hydrate and/or have limited contact with wort, then a reduction in utilization is likely to occur. This is pretty easy to address by simply making the netting large and non-restrictive, which it sounds like is not a problem in your case. In a crude sense you could line your kettle with a grain bag that could be removed after the boil to lift all of the hops out of the kettle similar to the inner portion of a lobster pot.

I don’t know how hops that end up in the trub pile in a whirlpool differ in their contribution of aroma and bitterness compared to hops that may be floating around in the whirlpool. In commercial brewing operations, even relatively small ones, pellet hops intended for late hop character are added to the kettle at the end of the boil and the wort is either pumped to a separate whirlpool vessel or it is pumped back into the kettle to cause the wort to swirl. Following this step the wort is allowed to rest for about 20 minutes. This rest period is long enough for wort movement to effectively stop and for the trub pile to form, and the total time from hop addition to the beginning of wort cooling is at least 30 minutes, usually closer to 40 minutes. This is ample time for aroma extraction and my guess is that hop aroma would not differ if an experimental beer were brewed with the same contact time with the aroma hops and no whirlpooling, and hence less hops in the trub pile.

There is a very real practical consideration with this question, however, and that has to do with the contribution of bitterness with aroma hop additions. Back in the days before ultra-hoppy beers many brewers, both homebrewers and commercial brewers, either ignored the contribution of bitterness of late hop additions or assigned a fairly low utilization rate for the addition. This made sense for most beers where the last addition was typically less than or equal to the other hop additions. A mistake in the assumed utilization was not a big deal because the last addition was not large enough to contribute much bitterness.

The truth is that aroma additions can significantly contribute to bitterness because the utilization of this addition can be much higher than assumed when pellet hops are used. Just check out some of the current tables about hop utilization and you will find that almost all of these tables relate utilization to boiling time, where late hop additions typically have predicted hop utilization rates around 5% based on a few minutes of boiling. The problem with this is that most of these tables show the utilization to be 0% with no wort boiling. While this is true of dry hopping, it is not true when hops are added to hot wort, as is the case with hops added at the end of the boil and hops added to the whirlpool.

My guess is that this mindset began before hop pellets became so prominent in the world of brewing. Some breweries still add pretty large, sometimes massive, late hop additions to the kettle using cone hops and almost immediately transfer the wort to a whirlpool or hot wort tank. During the transfer the cone hops are removed and the contact time with hot wort is greatly minimized. Instead of being in contact with hot wort for 20 minutes during transfer to the whirlpool, followed by a 20 minute whirlpool rest followed by up to 60 minutes during transfer to the fermenter (these are typical commercial brewery times) the contact time is about 20 minutes; a full 80 minutes less. This is a very significant difference as the utilization associated with the late hop addition increases from somewhere around 5% up to about 20%, depending on wort gravity and contact time with hot wort. Add this threefold difference in utilization to the sometimes incredible increase in late hop addition rates and the result is beers with a lot of bitterness directly related to late hop additions.

The cool thing about the hop spider is better control over your bitterness, if you are so inclined to want to nerd out! I am that sort of brewer who likes knowing how my beer is affected by what is done in the brewery. With the hop spider you can make those massive late hop additions, using pellets or cones, extract the aroma from the hops and pull the hops out from the wort before contributing bitterness that is not so easy to calculate. Hop on Spider Man!

 

Response by Ashton Lewis.