Dry Hopping – What is it and why do we do it?

You may have seen in some of our recent posts we’ve been talking about “dry-hopping” some of our seasonal brews like Ukuku & Cub, but what exactly are we talking about and why do we do it? 

Dry-hopping is by no means a new craze with evidence dating the practice back at least a 100 years, but whereas its purpose has changed from preservation to that of flavour it has also become much more prevalent over the last two decades with hop-forward styles dominating the market and arguably favoured by a majority of beer-drinkers. It would be unusual these days, for a brewery to not to utilise a dry hop in any of their product range.

So why do we add hops in the first place? In the process of making beer, we can add hops at various different times for different effects usually to alter Bitterness, Flavour or Aroma. During the boil, heat alters compounds called alpha acids within the hop that isomerise and form iso-alpha acids which give us the perception of bitterness in our beer. The longer we boil a hop, the more isomerisation occurs and the more bitterness we impart. 

But alpha acids aren’t the only useful compound within hops that we are looking to exploit. Hops are full of essential oils, mostly monoterpenes, that are responsible for the strong smell and flavour we associate with the Hop plant, these are much more volatile than alpha acids, and will evaporate and alter readily at high temperatures within the boil. So to account for this, we can move additions for flavour and aroma towards the end of the boil to try and retain some of those volatile compounds, or into a cooler whirlpool stage or even cooler still we can add during or post-fermentation.

The latter being what we refer to as “Dry-Hopping” – Simply adding Hops into beer at a cooler stage during or post fermentation.

Simple on the surface perhaps, but as brewers, we can play around with the parameters of our dry hopping regime to tweak our products to fit our brief. The main parameters at play are;

• Amount/Varietal – Our beers range from 2-10 grams/litre of dry hopping, which equates to around 6kg-30kg in a full batch. Generally speaking the more we add the more intense the hop flavour/aroma will be. We can also change which hop varieties we add and in what ratio to each other to build specific flavour profiles.
• Temperature – The temperature of the tank when we add hops, can affect how quickly and which oils we extract, in the higher ranges we can extract more of the fruity, citrus oils, whereas a lower dry hop temperature might give more grassy, pine and wood notes.
• Time of addition/ Contact Time– We can add hops at any point whilst the beer is in tank, most commonly we add “during” fermentation (around half way), at the “tail end” of fermentation (about a quarter remaining) or “post-fermentation” (when we have reached our final gravity or ABV), these differ in their effect due to a type of dark magic we call “bio-transformation” – when active yeasts interact with hop compounds they can transform them into completely new aromatic compounds with different properties. We can mix additions in a “Double Dry-Hop” at different stages to help us create products with a broad and interesting depth of flavour.
• If this is a great way to extract flavour compounds, Why wouldn’t we just do this all the time? Well with all good things there is a trade-off and Dry-Hopping is no exception.
• Cost – Hops are expensive things and when we add 30kg into a batch along with the original hot side additions, things can get pricey which as producers we then have to swallow or pass onto the consumer.
• Yield – Hops are also thirsty things, being plant matter, once added they expand and soak into the product and have to be crashed and filtered out of our final product, this means our yield is much much lower than that of an non-dry-hopped product. This combined with the high cost of manufacture again can lend itself to expensive liquid. 
• Process Complications – In short, a dry hop can sometimes be a right faff, getting them in with minimal oxygen ingress, getting them out again for the product to be packaged and cleaning dry-hopped tanks after is a pain. 

We also have to look out for an effect called “Hop Creep” whereby if we add a large amount of hop matter, we also add a large amount of enzyme found in the hop leaf or bract, these enzymes can break down previously unfermentable sugars, which any residual yeast will happily consume, leading to our gravity “creeping” down and our ABV “creeping” up. Not only is this an issue for the strength of our beer, but if done at lower than fermentation temperatures we could cause off flavours in our beer which wont be cleaned up by any active fermentation process, or even worse if we leave fermentable sugars in beer that is then packaged with residual yeast we could get re-fermentation in package, leading to off-flavours or even worse potential for popping bottles and cans which nobody wants.

All in all, there are pro’s and con’s, but such is life. Dry hopping when used effectively gives way to some incredible tasting beers, hopefully one of which is hiding in my fridge for me to go and seek out. 

Much Love 

Rob