Troubleshooting - Hop Creep

What is hop creep?

Hop creep refers to the phenomenon observed in the brewing industry where dry-hopped beers, especially those with high hopping rates, can undergo a secondary fermentation due to the release of fermentable sugars from the added hops. This unintended fermentation can lead to a range of issues in the final beer, including over-carbonation, diacetyl formation, extended fermentation time, and the potential for exploding bottles or cans.

Here's a breakdown of how hop creep occurs:

Dry Hopping: This is the process of adding hops to beer post-primary fermentation. These hops can contain fermentable sugars and enzymes.

Enzymatic Activity: The hops added during dry hopping can introduce enzymes like amyloglucosidase. These enzymes can break down the dextrins (longer sugar chains that yeast cannot typically ferment) present in the finished beer into simpler, fermentable sugars.

Secondary Fermentation: The yeast present in the beer can then ferment these newly available sugars. This fermentation process produces additional alcohol and carbon dioxide. Typically the beer ferments an additional 0.5 to 2ºP during hop creep.

The root cause of hop creep is amylase enzymes (e.g. amyloglucosidase) present in hop material when added to beer during the dry hopping process. These enzymes cause partial breakdown of longer chain sugars/dextrins which can now become fermentable. For example, maltotetraose (4 chain sugar, unfermentable) can be turned into glucose + maltotriose (both fermentable).

What impacts hop creep severity?

Hop creep can vary both in degree of creep (amount of additional fermentation, anywhere from 0.5ºP to 2ºP) as well as timeline (how long the beer takes to finish fermenting). The degree of creep tends to be impacted by upstream wort production process such as mashing procedures. The timeline of hop creep is largely dependent on yeast health and yeast management.

There are two main factors that impact hop creep severity:

1. Mashing procedures (temperature, thickness, and pH creating a wort rich in maltotetraose and other "almost fermentable" sugars)
   1. To mitigate risk of severe hop creep, we recommend targeting a standard mash thickness, mash pH in the 5.3-5.5 range, and ensuring complete starch conversion in your mash (avoid short or hot mashes).
2. Yeast management
   1. Poor yeast health will lead to a longer hop creep.
   2. In particular, ensure your wort has adequate FAN and Zinc. Several brewers have noted dramatic improvement in hop creep timeline when ensuring the right amount of zinc is added to the fermentor.
   3. Poor wort oxygenation before fermentation can also be a root cause of extended hop creep.