What A Lab Report Can Tell You About Hops

AAR Lab Blog Post - understanding hop COAs


HotMC: What drew you to brewing chemistry?

AAR: In the early 2000’s I had been working in a food chemistry lab and we received a request to analyze several beers for organic acids, I began a lot of research and found it to be both interesting and fun.


HotMC:  What made you decide to start your own lab?

AAR: At the time I was conducting research in many different areas of food and dietary supplement chemistry. Having the ability to drive and focus my own business, working directly with customers without interference. Simply helping people find the truth in what they do, really appealed to me.


HotMC: Can you describe the process of testing hops?

AAR: Hops are valued for their aroma (essential oil) and bitterness (alpha acids). At AAR, we use solvents to extract wet, whole cone or pellet hops, and then separate a portion of this sample extract on a HPLC (high-performance liquid chromatography). The machine separates and graphs the amounts of each acid on a computer which we then compare to known amounts. To evaluate the oil content, we have 10 steam distillation systems to boil and collect the oil that condenses over 4 hours. This is the “Total Oil in mL/100g”, and then a portion of the oil is analyzed by Gas Chromatography (GC). This allows us to quantify the individual amounts of each of the major essential oils in hops. The oil “fingerprint” is very consistent based on the variety of hops. We help people understand the differences from the expected amounts of the individual oils or terpenes and how these can be attributed to issues with harvest timing, drying, or pelletizing. This is the basis for our Aroma Quality (AQ) test package.


HotMC: What does the Hop Storage Index tell us?

AAR: Hop storage index is the ratio of oxidized vs. non-oxidized alpha acids. The result is obtained by looking at the specific wavelengths each form absorbs with a spectrophotometer. For example, an HSI of 0.300 could basically be interpreted as 30% oxidation.

Oxidation in hop acids and oils yields off-flavors: cheesy, onion, or wet cardboard aromas in a finished product. Therefore, a lower HSI means lower oxidation, and a better hop. In addition, HSI is beneficial to the grower and processor in terms of evaluating their processes, after each step, results for acids and HIS could be obtained to identify and hopefully resolve steps that cause losses or excessive oxidation.


HotMC: What is the importance of Cohumulone in Alpha Acids?

AAR: Cohumulone is one of the three different alpha acids that make up the “Total % Alpha Acids” result. The % of cohumulone in the total result is very consistent and different for each variety. For harvest timing it is quite important, as the amount increases as the hop ripens. When the cohumulone hits the expected range, it is ready to harvest. This can be particularly valuable information for a variety like Cascade that does not have a significant alpha acid “peak.” For Brewers, a hop with high cohumulone also is considered to impart a harsher first note of bitterness.


HotMC: On the results for the Columbus hops I sent in, the Cohumulone was a lower percentage than the typical range. Is there a common cause for that?

AAR: In most cases, this would suggest the hop was harvested too early. Yet, this also depends on where it was grown. The further South, the lower the cohumulone will be. This is one of only a couple clear examples we have found of "terroir" in U.S. hops. AAR Labs - US Hop Terroir

We are working to develop a sliding range for quality and harvest timing, but basically, folks growing at lower latitudes should aim for the lower end on the varietal range and conversely if you grow in the north, target the upper end for harvest.


HotMC: Does that impact the utilization or long-term storage of the hops at all?

AAR: No.


HotMC: What is the importance of Colupulone in Beta Acids?

AAR: Next year we hope to develop ranges for each variety of hops and use this data similarly to cohumulone as another harvest indicator and quality parameter.


HotMC: How do Beta Acids contribute to bitterness?

AAR: In the boil, beta acids are not nearly as soluble as the iso-alpha acids that form. These iso-alpha acids are the main source of bitterness. The role of beta acids in brewing is not well understood.


HotMC: Is there a significance behind the alpha/beta (a/b) ratio on a Certificate of Analysis (COA)?

AAR: These ratios are common tools used to evaluate harvest timing, quality, and varietal

specifications. The A/B ratio is more often applied in older methods that don’t include cohumulone analysis in the total acids result.


HotMC: Do the more detailed hop analysis reports that you run help farmers adjust their practices to help improve future crops?

AAR: Absolutely, our Aroma Quality (AQ) and Comprehensive profiles give growers and processors great insight to the effects on quality. Keep in mind we have analyzed hundreds of hop samples and the oil profiles for each variety are very consistent across the country.

Monoterpenes, myrcene, pinene and esters are highly susceptible to losses due to heat and friction during processing. These compounds comprise of the lighter flower/fruity bright first notes that are very important in balancing the herbal/spicy notes (sesquiterpenes) that often comprise of the finish in a beer. If drying or pelletizing is done at too high of temperatures, these compounds can be completely lost. This results in a much lower “Total Oil (ml/100 g)” content. In addition, it yields a brew that has no front-end brightness, and leaves a one note herbal finish on the palette.

By testing hops at each step of the process, hop growers and processors can tune their oasts and  die temperatures to yield the best results. Our AQ reports provide direct comparisons to the expected varietal ranges which allows growers and processors to adjust time and temperature settings to maximize quality and improve throughput. It a balancing act, but small growers should be seizing the opportunity to use low or no temps, as they are typically not as pressured to get hops processed quickly through the drying step.


HotMC: How much variation do you see from year to year in a hop yard?

AAR: After a year or two of conducting some pre-harvest tests, typically, a grower can narrow down a 7 to 10-day window that is reliable for each variety year after year. Harvest timing and the ability to dry hops to an 8 – 12% moisture level are the two most critical steps to be successful. Harvesting too early or late, or a poorly dried hop, can yield an unsellable product.


HotMC: Is there a drop off in variation after the plans are established, say after three or four years?

AAR: First year crops are typically low in acids and oils, especially the high alpha varieties. Noble varieties and Cascade typically do OK, but are low in oil.

Second year, and beyond the plant matures and alpha and oil production typically hit the mark and continue to improve.

From year to year, we’ll see better crops for a particular variety in a particular region. It’s cool, because when one variety has a down year in let’s say the Pacific Northwest, typically that variety will have a great year somewhere else. “Don’t put all your eggs in one basket” applies to the hops industry as a whole and on a smaller level, the diversified grower with multiple varieties in production. This will allow the industry to keep a stronger supply chain, and elevate the number of high-quality flagship brews.


HotMC: In addition to testing hops and beer what else do you do at the lab?

AAR: As a TTB Certified Chemist and Laboratory we conduct many tests on a variety of beverage products, including wine, ciders, seltzers, kombucha, and mead. We produce full “Nutritional Facts” panels & conduct legal testing for interstate and international commerce. This winter we are expanding our capabilities to include volatile off-flavor analysis,vicinal diketones (VDK’s) and much more.


HotMC: Do you brew beer as well? If so, what do you like to brew?

AAR: I am very interested in setting up a small system, and hopefully within the next year we’ll have something up and running to experiment with or just have fun. I’d like to try Belgium styles; IPAs and experiment with various dry-hopping techniques.


HotMC: What else should we know?

AAR: My goal with AAR is to provide access to high quality analytical services at a great price to anyone who wants to produce great products.


Hop Certificate of Analysis for Columbus
Hop Certificate of Analysis - 2020 Kansas Grown Columbus Hops

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