Dry hopping is a term we hear and use a lot when it comes to craft beer. Let's take a closer look at it, so that it can give you some ideas too, maybe 😉
Article written in collaboration with Alexandra Berry
Overview
As we all know (sisi ;-)) hops are composed of essential oils which bring theAromatic, andalpha acids which when isomerised give the bitterness to the beer. This isomerisation takes place at a temperature of over 85°. Thus, the earlier the hops are added to the boil, the more bitterness they will impart. However, hops contain terpenes and hydrocarbons such as linalool, myrcene, humulene and geraniol, which evaporate during the boiling process. Myrcene is the most abundant essential oil in hops, accounting for up to 60% of the chemical composition of the gland, and is the most likely to be affected by over-boiling. Each of these components imparts particular flavours to the hops which are found in the finished mastered product. If added too early in the boil, they will have no impact Aromatic on the brew. On the other hand, when added to a cooled brew during fermentation, these aromas are sublimated and are easily extracted when in contact with the liquid.
Dry-hopping is a technique that consists of adding hops after the boil, i.e. during fermentation or when the beer is put in the cask. This short contact with the beer allows the flavours to be extracted without too much bitterness or astringency. The dry hop can last a few days at a temperature of between 4 and 20°. It is advisable to stir the beer once a day in order to promote the extraction of the components.
However, it is possible to use hops with a high alpha acid content in a hot dry hop. This will allow the acids to be isomerised to add bitterness, while revealing the aromatics of the hops.
It should also be kept in mind that during a dry hop, the yeasts are still active in the fermentation tanks and can transform the hop components. The brewer must therefore decide whether to keep or remove the yeast before dry-hopping.
There are no restrictions or recipes to follow for dry hopping; it is up to the brewer's creativity to imagine what type of beer he wants to obtain and what aromas he wants to emphasise. In order to control his dry hop, the brewer must know the chemical characteristics of the chosen variety (its aromatic components and itsalpha content) but also its place of origin, its harvest date, its ideal isomerisation temperatures...
The technique can also be adapted to the type of equipment used by the brewery and the quantities brewed. It is a technique that seems to be made for microbreweries: the more the hops are in contact with the liquid, the more they can transfer their aromatic compounds. It is therefore perfectly suited to small tanks.
The suspended yeast can, however, metabolise the dissolved oxygen, thus preserving the beer from oxidation.
Shape of the hops
The hops used for dry hop can be in cone or pellet form (or even in extract):
- The cone offers natural extraction but will tend to float to the surface absorbing more must. Thus, during filtration, the loss of liquid is quite high (about 7%).
- The pellets will dissolve, which leads to a better extraction of its components. On the other hand, the pellets can cloud the beer if a cold crash is not performed after the dry hop.
For dry hop, pellets are generally recommended. As the hops have already been crushed, their lupulin mixes easily with the liquid for a better extraction Aromatic.
The extraction is between 5 and 10% more efficient with the pellet than with the cone.
Whatever form it takes, it can be contained in a hop bag, a hop tube or added directly to the wort. The hop bag makes it easy to remove all the hops, but limits the extraction and contact of the components with the liquid (not to mention the fact that the bag becomes very heavy to take out of the vat soaked when going over large quantities).
Different Dry Hoptechniques
Duration of the Dry Hop
The extraction of compounds during raw hopping takes between 1 and 3 days. Several studies have shown that the greatest extraction takes place within 24 to 36 hours. Thus, hops can infuse for 3 to 5 days, but it is not advisable to leave them longer, as this may give the beer a grassy taste.
The ideal temperature is between 10 and 14° to avoid hop creep.
Hop Creep: when hops release enzymes that hydrolyse dextrins. This transformation produces fermentable sugars, called over attenuation. This leads to a taste defect, a change in alcohol content, and above all the creation of CO2. It is best to keep the hops in contact with the beer for 3 days at a temperature of about 10°.
HotDry Hop: first fermentation
A hot dry hop consists of adding hops at the end of the boil, in a beer at about 19°. In this brew, the yeasts are still active and feed on the sugars extracted from the hops, thus causing fermentation. The pH, alcohol content and mash density will therefore be altered accordingly, as well as seeing a greater concentration of hop components and an increase in alpha acid content (and therefore perceived bitterness).
This primary fermentation is accompanied by agitation and CO2 production. Both will have an impact on the evaporation of the essential oils and will result in a loss of flavour.
ColdDry Hop: second fermentation or storage
In order to extract and enhance theAromatic of a hop, it is advisable to do raw hopping at the end of the secondary fermentation, or in other words the ageing period.
Once the hopping is complete, it is advisable to cold crash the brew, which consists of lowering the temperature for a cold storage. The particles suspended in the brew will fall to the bottom of the tank to obtain a clarified liquid.
It is advisable to make a cold crash of 2-3 days at a temperature of about 3° before packaging.
Dry Hop static
Static dry-hopping refers to simply adding the hops to the fermentation tank. Stirring is usually done by hand, so this technique reduces extraction time but involves contact with air and therefore promotes oxidation of the hops. This can lead to the extraction of polyphenols and therefore more herbaceous and astringent aromas. To avoid this, some tanks allow the addition of hops from the bottom, which allows contact with the liquid without the risk of oxidation.
Dry Hop Dynamic
Invented in the 2000s, the dynamic dry hop circulates the beer between the fermentation tank and an external unit containing a filter. The latter can be tangential or plate filter, in which the hops are placed. The circulation of the beer between the two units allows for better extraction, hopping and the required quantities of hops (-50% compared to static).
Hop Gun
The use of the hop gun is recommended for traditional tanks because the addition of hops is done by CO2. This allows the residual oxygen to be expelled and all the aromas to be retained. However, the addition of CO2 can lead to an increase in foam in the finished product.
Iso-Mix External Drive
In 2017 the ISO-MIX EXTERNAL DRIVE was created; a rotary jet mixer that is placed under the tank. This allows the solids to be dispersed with a homogeneous suspension of the hops in the tank. This reduces the required doses by 20% and the hopping time by 15%. In view of the cost and operation, it will be of most interest to large breweries with large tanks and capacities of 100HL.
Warnings
Raw hopping, although used to flavour the beer, can however increase the perceived bitterness and measured bitterness of the brew through the transformation of its components. Hops are a bittering plant, and any addition of hops also adds bitterness 😉
A dry hop can be very frothy and if not properly controlled can lead to gushing, you know, when the beer gushes out like a hop fountain!
Dry Hop, Double Dry Hop, Triple Dry Hop...
So we get it, the dry hop consists of adding hops to the brew after it has been boiled, but with the fashion for IPAs and aromatic American or New Zealand hops, many brewers are going much further.
As mentioned, it is quite possible to hop during the first fermentation in order to add a little bitterness and to bring out theAromaticof a beer, before proceeding to a second hopping during the aging process, before the cold crash, in order to emphasize only the aromas. For this second hopping, varieties with very strong characteristics are used: Nelson SauvinSorachi, Sabro, Citra® or Motueka among others.
For a triple dry hop, not surprisingly, three stages of hopping are required. The last one can be done just before packaging.
Each brewer will find his or her preferred technique depending on the Aromatic profile he or she is looking for, the equipment available and the hop varieties chosen. With the expansion of hop research and innovation, the recipes are multiplying and allow us to discover new flavours in our glasses every day.
For more information...
Janis, S., (2019), The New IPA: Scientific Guide to Hop Aroma and Flavor, ScottJanish.com.
Hieronymus, S., (2012), For the Love of Hops, The Practical Guide to Aroma, Bitterness and the Culture of Hops, Brewers Publication.
Steele, M., (2012), IPA Brewing Techniques, Recipes and the Evolution of India Pale Ale, Brewers Publications, Boulder, Colorado.
https://wildabouthops.nz/dry-hopping-beer.html
