Hop Growers of America

Happy Hopping for Craft Brewers

February 24, 2021

Happy Hopping for Craft Brewers

Navigating Bitterness and Balance when “Ramping up the Hops” – Practical Tips for Brewing your next Hoppy Brew

Introduction

     Hops (Humulus Lupulus) can enhance and complete a beer to perfection or poor execution and imbalance can distract and ruin an otherwise perfect brew. The hop plant plays many roles in beer. First, is the responsibility of the hops to provide bitterness or lack thereof to the beer for balance. Second, is the decision to bring hop flavor to fruition or diminish it. Lastly, the ever-so-desired hop aroma we have grown to love offered up by late hop additions and/or dry hopping is manipulated. Needless to say, it is imperative that the craft brewer understand how to calculate bitterness, enhance or dissuade both hop flavor and/or aroma. Knowing how to maneuver hops throughout the entire brewing process is a must for the modern-day craft brewer.

Bitterness

     Hops contain alpha-acids that are converted to iso-alpha acids during the boiling process, as well as during whirlpool and hot stand, post boil. Isomerization of alpha-acids to iso-alpha acids occurs when the hop resins, which contain the alpha-acids, are heated, changing their molecular geometry and making them soluble in wort. Isomerization begins at 79.5C and reaches its maximum potential at boil (Palmer 75, 2017). Pro Tip 1: The proper amount of bitterness measured as International Bitterness Units (IBU's) is crucial in creating a well-balanced and highly drinkable beer. To calculate a more accurate IBU rating, many things must be considered. First, the brewer must know the alpha-acid percentage of the hop they are planning on using. This information should be provided to the brewer by the seller via a QC code located on the hop bag and/or an information sheet provided along with hop shipment. For g/L calculation for IBU: BU=weight of hops x % AA x % utilization x (10/final volume).

For oz./gal calculation of IBU: BU=weight of hops x % AA x % utilization x (75/final volume).

Example: Jennifer's Ale calls for 2oz. (1oz=28gr.) of 7% alpha acid cascade hops, boiled for 60 minutes, assuming a 30% utilization rate for a 60-minute boil with a final volume of 38 Liters.
*BU= 56gr x 7% x 0.30 x 10/38
56gr x 0.07= 3.92
4.06 x .30=1.18
1.18 x .263=.31
31 BU

      Pro Tip 2: When boil times are reduced and original gravity vary, utilization rates must be adjusted accordingly. For an in-depth dive into calculating utilization rates based on boil time and original gravity please review the work by Glenn Tinseth cited below or John Palmer's 5th Edition" How to Brew" 79, 2017. For a generalization to quickly calculate utilization rates use the following guide. Boil times of 30 minutes or greater=30%, 20-30 minutes=25%, 15-20 minutes=20%, 10-15 minutes=15%, 0-10 minutes=10%, above 79.5C Stand/Whirlpool=5%-10%. The above guide and calculation to determining ones BU content is not the complete story behind how bitterness can present itself in a beer. Recent research indicated in Scott Janish's book, The New IPA: A Scientific Guide to Hop Aroma and Flavor, reveals that dry-hopping rates above 2#/bbl. reduces the iso-alpha present in a beer due to the addition of humulinones, resulting in less bitterness (Janish, 125 2019). In addition, some brewers and hop researchers believe that quality of bitterness is tied to the hop variety and also, placement of hops in the boil. Traditional techniques for bitterness development placed noble-type hops, which typically have lower alpha acids, at the beginning of boil. Pro Tip 3: I tend to develop soft, high quality bitterness when over 50% of my total BU's are placed no later than 30 minutes to end of boil.

Flavor and Aroma Development

     It is commonly known that late hot side hopping can increase both hop flavor and aroma. I do believe through my brewing trials this to be true, especially in my session beers. Recent research with 34 commercial lager breweries cited in Janish's book, revealed dry hopped beers had the highest level of phenolic, polyphenol and humulinone concentration, presenting a harsh bitterness experience in sensory analysis. The same study revealed that beers using tetra and pre-isomerized iso-alpha acids compared to traditional late hot side hopping, displayed a smoother bitterness (Janish 106, 2019). The suggestion was put forth that when a beer is being produced to enhance hop aroma and dry hopping is going to take place, it may behoove the brewer to reduce late hot side hopping. Although late hot side hopping can increase hop flavor and aroma, it is important to remember it also raises total iso-alpha acids, increasing BU level. Although the research measuring the qualitative sensory analysis of quality bitterness vs. harsh, astringent bitterness due to late hopping is limited, I have always perceived late hot side hopping to produce a harsher bitterness.

    Pro Tip 4: Therefore, when deciding how to impart hop flavor and aroma into hop forward beers, I suggest placing approximately 20% of total hop BU's 15 min to end of boil, inspiring hop flavor and 15% of total BU's at end of boil and whirlpool. In addition, hop varietal, along with total polyphenol and humulinone contribution, should also be considered when discussing quality of hop bitterness. A study contemplating late kettle hopping with liquid carbon dioxide hop extract revealed that late kettle hopping is important in hop flavor development when compared to only utilizing a dry hopping method (Janish 41, 2019) 

     Pro Tip 5: Using a **hop back before the heat exchanger and flowing the finished, hot wort through whole flower hops prior to being cooled can also greatly increase hop flavor and add to an increase in hop aroma.

Dry-Hopping Techniques

Dry-hopping is the process of adding hops to the cooled wort and/or beer, post boil after cooled or post fermentation. There are many opportunities and techniques for adding hops after the wort has been cooled and/or fermented to enhance hop flavor and aroma

     (Cold Side DH) When cold side dry-hopping upon knockout, prior to fermentation at one of the breweries I managed, the sensory analysis of this particular dry-hopped beer was quite grassy and vegetal. The grassy character became a signature flavor feature of the beer. Temperature is an important factor to consider when dry hopping a beer to properly attain the type of hop aroma the brewer is looking for and should be considered when deciding the proper dry-hopping technique to employ.

     (Recirculation DH) Another dry hopping procedure used amongst craft brewers in North America is adding either whole flower hops into a * "hop back" or hop pellets directly to the beer, approximately 2-3#/bbl., post fermentation and recirculating the finished, dry hopped beer. I conducted a sensory analysis experiment where my team pulled a sample of the warm (19C) ale to be dry-hopped prior to dry-hopping and a sample every 3 hours during recirculation. Samples were pulled at 3 hours, 6 hours, 9 hours and 12 hours and compared to the control, non-dry-hopped sample. We conducted the experiment 2 different times on the same ale, which was fermented with 1056 (similar to SR 005) with the same hops. It was a unanimous decision that recirculating the hop pellets for 3 hours made a mild difference in hop aroma and flavor. The largest jump in amplified, pleasant fruity aroma and flavor from the cascade hops used was seen post 6 hours. It should also be noted that very little difference was perceived after 8 hours. The recirculation process can work very well to amplify hop aroma and flavor however, it is crucial that no oxygen enter the recirculation loop at any moment. In addition, it is important that all recirculation equipment and hoses used have been thoroughly cleaned and sanitized prior. Lastly, the recirculation should be conducted softly, approximately at 35 hz./minute.

     (Tank Pellet DH) One of the most common ways to dry hop in N. America occurs after fermentation is complete and diacetyl rest (24 hours post fermentation) is complete, the beer is cooled approximately 3C to encourage the yeast to flocculate to the bottom of the cone. The yeast is collected so it can be used again, the tank is SLOWLY evacuated of any CO2 in the vessel. Once the yeast is out and there is no pressure in the vessel, hops are added thru a port by a brewer on a ladder.

     Safety Tip: This is a 2-brewer job. It is imperative the brewer on the ladder has an attendant to hand hops to him/her, to protect against a fall and it is preferred that the brewer dry-hopping is harnessed in if the fermenter is tall. In addition, if the beer being dry hopped has carbonated in the fermenter, it very likely that once the hop pellets are added they could provide the co2 a nucleation site to adhere to and cause an eruption of pressure. This can be a very dangerous process and all safety measures must be taken to protect that this eruption does not occur. Once fermentation is complete with a soon-to-be dry hopped beer, no more than 3-5 PSI head pressure should be placed on the beer. If the head pressure rises too high prior to dry hopping, it is highly likely an eruption will occur when the hop pellets are added and could harm the brewers. Please do not take this lightly. In addition, there is an extreme loss in beer volume when an eruption happens.

     (Hop Cannon DH) One of the best ways to prevent any injury from an erupting tank is to use a device called a hop cannon for dry hopping. Please realize that “hop cannon” is just a name and other similar, stainless steel small infusion vessels that can hold pressure, can be used as well. Reach out to your equipment provider(s) for ideas on what works for your brewery. In this instance, the brewer usually does not need an attendant and stays on the ground while adding hop pellets to the fermenter. This piece of equipment needs to be purchased by the brewery and it needs to safely hold enough pressure to send pellets up the side arm of the tank and into the beer. Eruption can still occur if the beer has enough carbonation and beer loss will occur, however, the brewer reduces their risk of injury greatly. There are numerous brewing equipment manufactures in North America and beyond that produce different size hop cannons. After removing any pressure from the fermenter prior to sending the hops up the arm, the side arm valve must be removed from the vessel to allow hop pellets to easily rise to the top and not clog the butterfly valve. A larger hose is usually needed for this process, a 2 to 3-inch hose usually suffices.

     Quality Tip: When introducing hops after fermentation, it is very important not to introduce oxygen to the fermented beer. One way to reduce this introduction is by having positive co2 flow entering the vessel while upper ports are open, to create a co2 environment Co2 is heavier then air and this will help protect the beer from becoming oxygenated while the hop pellets are being poured into the vessel. When using the hop canon, it is suggested to "bubble" co2 thru the hop pellets in the cannon from bottom ports installed on the cannon, 10-15 minutes prior to sending the hops up thru the tank side arm and into the beer.  

(End of fermentation DH) Recently in the last 3-5 years, many brewers have been trying their hand at adding hops 1-3 plato before fermentation is complete. The goal is to encourage the interaction between active yeast still in suspension and hop-oil derived compounds, otherwise often generally referred to as bio-transformation (Hieronmymus 26, 2012). Although the subject is too large of subject to breach here, it does ignite a large conversation within a group of brewers. Recent research released in 2017 by The Journal of the American Society of Brewing chemists on hop timing further indicates that whirlpool hopping is what encourages the biotransformation process. Their findings concluded hops must be added to the whirlpool, not at the end of fermentation, to gain the most from the bio-transformation of geraniol to B-citronellol (Janish, 49, 2019).

Conclusion

When deciding to ramp up the hop bitterness, flavor and/or aroma of one’s beer there are numerous variables to take under consideration. For instance, one must consider the hop varietal being used, total oil content, process, temperature, volume of beer, contact time, grist make up and more. I encourage brewers to try simple, affordable techniques that fit their brewery and budget. If the results are pleasing to the beer, then keep forging on. What works in one brewery and for one beer, might not necessarily be work for another. Clearly there are many paths to take when using one of beers most elusive ingredients. Good luck and happy, safe hopping!

**Hop Back: a small, closed vessel that houses a screen basket inside which can hold back the leafy material of whole flower hops during a recirculation or pass thru of hot wort. There needs to be a port on the top of the vessel, as well as exiting the vessel so hot wort or finished beer can pass through the whole flower hops.

Janish, Scott. 2019. The New IPA: A Scientific Guide to Hop Aroma and Flavor. ScottJanish.com.

Hieronymus, Stan. 2012. For the Love of Hops: The Practical Guide to Aroma, Bitterness and the Culture of Hops. Boulder, Colorado: Brewers Publications.

Tinseth, Glen "Glen's Hop Utilization Numbers," 1995 accessed Palmer, John)"How to Brew" 5th Ed. p.77, 2017.

Author Bio: Jennifer Talley’s brewing career began in Utah as brewmaster at Squatters Pub Brewery in Salt Lake City. She honed her skills through a variety of positions at Salt Lake Brewing Company, Redhook Brewery, Russian River Brewing Company and Auburn Alehouse in Auburn, California.
With more than 20 awards from the Great American Beer Festival® and World Beer Cup℠, Talley is also a Cicerone Examiner, craft beer industry speaker, technical committee member for the Master Brewers Association of the Americas, and a national and international beer judge. Talley was awarded the Russell Schehrer Award for Innovation in Craft Brewing in 2011.
She is the author of Session Beers: Brewing for Flavor and Balance and currently sits on the Board of Directors of the Brewers Association, and is the owner/brewmaster at Talley Fermentation’s in Grassvalley California.

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