Research of Methods to Improve the Processing of Hops (Humulus lupulus L.)

Project Overview

Project Type: Farmer/Rancher
Funds awarded in 2017: $7,500.00
Projected End Date: 10/31/2019
Grant Recipient: Hines Hops Farm
Region: North Central
State: South Dakota
Project Coordinator:
Yvonne Hines
Hines Hops Farm


  • Agronomic: hops


  • Farm Business Management: value added

    Proposal summary:


    Current methods to process hops involve using heat, which causes some of the valuable oils to evaporate and degrade the quality of the product. The hops produce lupulins, or oils that give beer it’s flavor. Specifically for brewing, the two main oils are alpha and beta oils. These oils are fragile and begin breaking down at 120°F and degrade completely at 140°F. This is a necessary loss for large-scale operations, and farms in humid areas.

    There are two stages of hops processing that involve heat levels that degrade the oil content. The first is during the drying or oasting process. Large operations force heated air through the hops cones on drying racks; resulting in over-dried hops on the bottom, properly dried hops in the middle, and wet hops on the upper part of the hops layer. The hops are then mixed, resulting in appropriate moisture levels overall for pelletizing, 8-12%. The second part of processing that can degrade oil levels is the pelletizing. Current methods run the hops through a hammer mill to pulverize the cones, and then are transferred to a pelletizer. The pelletizers commonly used in the hops industry are the same as those used to make wood and alfalfa pellets, which generate enormous amounts of heat. To control this, hops processors cool the machines by frequently stopping the equipment, or use liquid nitrogen. Both of these solutions are time consuming and expensive.

    Experimenting with the methods of processing hops can result in a higher quality product, giving small producers an edge over the large established producers. Providing a premium product to brewers will help strengthen and grow the small-scale hops industry. Also, developing equipment and methods specifically for hops pelletizing could eventually benefit the entire hops industry.


    This harvest season I intend to address both phases of the processing that degrade the lupulins. First, to improve the oasting method I want to experiment with high airflow instead of heat to dry the hops. I will accomplish this by building drying boxes with screen bottoms, and use fans to provide airflow. After the cones are harvested, they will be placed in the racks and stirred occasionally to ensure even drying. I will closely monitor the moisture levels, and will introduce heat with propane heaters only as a last resort to save the crop if the airflow oasting fails.

    To address the pelletizing process, I will use a pill-making machine to create compressed hops tablets. The pillmaking machine will generate some heat during the compression, but significantly less in comparison to traditional pelletizing machinery. Once I determine if making tablets at low temperature is successful, I will then focus future research towards economic feasibly; including time to produce the product, cost of equipment, electrical consumption, etc.

    To properly compare my tablets with the pellets, I will have a portion of my harvest pelletized using traditional methods. I will compare the weight of the hops that enter the processing with the final output. I will also send samples for lab testing to obtain lupulin (alpha and beta) levels.

    I will provide these tablets to the head brewer at the Firehouse Brewery, Mike Kilroy, and a home brewers club called the Ale Riders, both in Rapid City, SD. Their feedback will be valuable in determining how the tablets compare to pellets. I too will be brewing identical batches of beer, with the only difference being pelletized or tablet hops. Again, the Ale Riders will help me compare the flavor of the different beers.

    Project objectives from proposal:

    1. Improve the quality and value of hops for brewing by experimenting with low temperature methods of oasting and pelletizing to increase the final oil content.
    2. Make local hops a more desirable, valuable, and profitable product for growers and brewers alike by researching ways to improve the quality of the processed hops.
    3. Keep more money in the local economy by encouraging brewers to spend funds on local hops rather than import hops from the west coast, and create seasonal and full time job opportunities through expansion of hops farming.


    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.