Dry Hopping is a crucial part in producing successful Craft beers, especially IPAs. It is an explosive experience for the gustatory system to taste and enjoy all the different fruity, floral and spicy notes which can only be achieved with Dry Hopping. Dry Hopping means adding the (dried) hops in the finished beer. Now you can imagine there are so many ways to do this! Every brewery has developed their own way of implementing dry hopping into the brewing process. It is a process that requires a lot of effort and tweaking.
These are the primary questions for the brewer:
1) Which hop form do I use (cones or pellets or even extract)?
Yes, it makes a difference if you use cones or pellets. There is a lot of romance and nature involved in using cones, but in terms of handling, efficiency and quality you are better off using pellets. Pellets are homogenized and securely packed without oxygen and will give you a pretty consistent flavour. They dissolve quickly and the process of extraction takes place much more efficiently than with cones. Using extracts is also a possibility, many aroma extracts are available, however they often don’t deliver 100% of the dry hop flavour. Very good results can be achieved with a combination of 50% pellets and additional hop aroma products.
2) How much do I put in, based on which criterion, at which temperature and for how long?
Most brewers determine the amount of hops they use for dry hopping on a gr/hl or pounds/bbl basis. Note that hops are an agricultural product and the oil and alpha content of each variety will vary from year to year. The oil composition will also be different every year. Therefore, hopping at a set amount of gr/hl will bring in a different level of flavour intensity for each crop year, maybe even for every batch. The best compromise therefore is to define the amount of hops according to the oil content. E.g. 2ml of hop oil/hl is a good starting point for a dry hopped beer. This means, if the variety you have chosen to use has an oil content of 1 ml/100g. You need 200 g of this hop. The hop oil content can be determined by your hop supplier.
Also, the temperature plays a crucial role in dry hopping. Everything between 0-25°C is possible. The colder the temperature of course the longer the extraction process takes. At higher temperature you might extract additional flavour’s that support the spicy and herbal characters, colder temperatures seem more beneficial for fruity characters. The duration of dry hopping depends on your system. A lot of breweries use a circular extraction, where the beer is either pumped through a chamber with hop pellets/powder, or where a hop slurry is pumped in circles. In dynamic systems like this the extraction is completed after a couple of hours in contrast to static dry hopping where the hop pellets are in the lager tank for up to 14 days.
3) How can I decide when the extraction is completed?
In terms of achieving the right level of bitterness we can measure that with the IBU method or HPLC. With hop aroma components it is way more difficult. With a sophisticated GC system, you are in the position to quantify components like linalool, geraniol, myrcene etc. However, the resulting flavour depends on the exact mixtures of numerous hop aroma components and cannot be measured with single or even a high number of concentrations of single components. It is much easier to use a trained tasting panel for this purpose. Sensory data is very reliable and connects you closely to your product. We have developed a Barth Haas Tasting Scheme that you can train with your panel. www.barthhaasgroup.com
4) How can I remove the hops and minimize the beer losses?
Many breweries use a centrifuge to separate the hops from the beer. However not every brewery can afford one. A good portion of hops can be separated together with the yeast in the conus of the fermentation/lagering tank. In terms of beer losses, it is more beneficial to work with pellets instead of cones. The different equipment suppliers are developing different solutions to minimize the losses.
Since the practice of dry hopping has found its ways into brewing science, many brewing scientists around the world are looking into the different aspects of dry hopping:
- What are the key aroma components in dry hopping?
- How to improve efficiency in dry hopping – less hops; same flavour
- Development of hop products that impart the same flavour intensity as original hops
- Characterization of hop varieties in regard to dry hop flavour properties
Having answers to all this question will help the brewing world to efficiently produce more incredible dry hopped beers!
In general, every hop variety is suitable for dry hopping. The distinction between aroma and bitter varieties is slowly becoming obsolete. And classic bitter varieties can give a powerful and pleasant dry hop aroma. Also note that the alpha content in a hop variety correlates with the oil content. So, varieties like Herkules with a high alpha content also have a high oil content. A lot of the so called flavour varieties (e.g. Citra, Mosaic, Topaz) not only have a high oil content but also a high alpha content. Also, the new German Flavour varieties as Mandarina Bavaria, Hallertau Blanc, Comet and Monroe have impressive Dry hop flavour potential and herald a new area of German hop varieties!
Because of the vast variety of hops, brewers need to a tool to investigate the hop aroma and its suitability for dry hopping in their new or existing beers. Simply done, a coffee press is filled with your beer and your favorite hop to replicate dry hopping without risking large amounts of beer. Add the hops at a dosage equivalent to the normal batch (we recommend to dose on oil, i.e. 1 ml/hl for decent hop aroma). Wait for one hour and then taste. You can save time and beer and achieve similar results to normal dry hopping!