The long road to Descriptive Profiling, part II

This is the second part to a three (?) part set of articles covering how to train a sensory panel to perform descriptive profiling.  It covers Intensity training and descriptive profiling lexicon (ballot) development.

Part iv:  Intensity

As confidence and flavor familiarity builds among your panelists, it will be time to add a new twist to the training regimen:  intensity training.   If we are to build flavor profiles for our brands, we need to be able to quantify the magnitude of the flavors that are found in the samples, so just as we sought consensus in how our panelists describe the flavors, we must now seek consensus in how we rate their intensities.  And just as before, we must use standardized materials and lots of discussions.

The first thing you’ll have to decide when you begin intensity training is what scale you will be using, and care should be taken when deciding so that you do not settle on one that is too narrow or one that is too wide.   If a scale is chosen that is too narrow, it will be hard to find differences between samples.   An intensity rating of 4 on a six-point scale (0-5) is only one step from a 3, despite being about 17% of the available scale.  Similarly, if a wide scale is used, you may find difficulty in getting all your panelists to use the scale the same way; some may prefer to use the upper portion of the scale while others are more comfortable using values at the low end of the scale, leaving room at the upper end for the potential of more extreme samples.

Many sensory scientists like to use an 11-point scale (0-10) because it’s pretty intuitive for us base-10-thinking humans, and it’s pretty close to the “sweet spot” in terms of the size of the scale, as discussed above.  For my panels, I prefer to use a 16-point scale (0-15) because it can be used with the Spectrum Method of intensity training, which is a standardized system for intensity training using widely-available materials as anchor points on the intensity scale.   For example, the aroma intensity of dehydrated milk powder is considered a 4 on this scale, the aroma intensity of Triscuit crackers is an 8, and the intensity of the cinnamon aroma in Big Red gum is a 12.  For each profiling panel, I have examples of these products in small jars on the table for my panelists to reference whenever they need to recalibrate their “intensity meters”.  Other examples of products that can be used to anchor the Spectrum intensity scale are found in Sensory Evaluation Techniques, by Meilgaard, Civille & Carr (CRC Press).

Once you’ve chosen a standard intensity scale, it’s time to see what your panel can do with it.   I start by spiking a few flavors that they are familiar with into beer.  For each flavor that I use, I create a couple of spiked samples at two different concentrations.  I choose levels that are known to be distinct enough for your panelists that they should generate intensity ratings with a significant disparity between them.   During panel, I present these “intensity pairs” of attributes to the panelists and ask them, using the standardized and accepted intensity scale, what intensity they perceive the added flavor at.  As the panel gives their feedback, I record their ratings on a whiteboard so we can all see the variation.   If there are any panelists who look like they are outliers from the group, they should be directed back to the intensity standards (like the Big Red gum) and asked to confirm their rating.  If they are still rating the flavors much differently from the rest of the group, you have some choices:  you can try to get them to bring their scores in line with the panel, or you can accept their uniqueness and let it be included in your data.   After all, everyone is genetically unique, and that uniqueness often translates directly to uniqueness in their ability to detect certain flavors.  One potential pitfall from the latter approach is particularly troublesome if you have small and fluctuating panel attendance.   If, for example, one of your few panelists is very sensitive to the butteriness of diacetyl (tends to rate it high) and you include their normal ratings into the brand profiles, and then later you assess some samples without that panelist present, their lack of influence will be felt in the data by way of artificially lower diacetyl ratings for those samples and your samples will seem “off profile” when in reality you are just missing an influential panelist.  Careful attention to the data your panelists generate is essential, and you will likely face several judgement calls along the way.

In addition to presenting spiked samples to your panelists to investigate their usage of the intensity scale, you can present non-spiked samples of your various brands, preferably ones that have specific flavors that stand out from the others – things like coffee beers, or sour beers, beers with flavor extracts or other flavorful additives.  These are a good segue into full-on flavor profiling of your brands –just choose a specific flavor to focus on and discuss.

One question that you’ll likely face from the panelists who are paying attention is:  “Should I be considering the extreme ends of the scale as ‘what is possible in beer’ or ‘what is possible in anything’?”   For example, if we’re rating the intensity of carbonation, do we consider a 15 (or whatever your scale’s maximum value is) to be the highest carbonation found in beer, or the highest carbonation level imaginable?   Sourness:   is the maxmimum considered to be something from an intentionally soured ale, or something like straight lemon juice?    There is no perfect answer to this, and chances are that some flavor attributes will lend themselves better to the “in beer” approach, while others may work better with the “absolute” approach.   The only thing I can suggest is that you open these discussions with your panelists (with appropriate standards in front of you), find some consensus that everyone understands and is willing to follow, and strive for a consistent application of your decision.

As I eluded to previously, each person has a unique response to a given flavor, and the differences between people can make life difficult for taste panel leaders.  If you can find and train enough panelists (10 or more) then the variation between panelists is probably going to be fine and won’t affect the data too much if people come and go.  The data you generate in profiling is an average of all your panelist’s scores, so as long as each of your panelists is consistent in their use of the intensity scale then individual variations will just become part of your data and won’t cause any discernable problems.   Issues arise, however, when your panelists are not consistent in their ratings or when you have a small panel with poor attendance levels.


Part v:  Lexicon development

The first thing to do when arriving at this next level is to pick one or two brands to focus on first, usually your high-volume flagship brands.   Once you’ve decided which brands to look at first, put several samples of them in front of your panel and through intensive discussions you’ll build a lexicon of attributes that apply to those products.  You should ideally have several flavor standards present so that the panelists can reference them in their discussions.  Write down each of the suggested attributes on the whiteboard and when the list is finished you’ll need to help the panel decide which of them are the most appropriate flavor attributes to describe the flavor of your brands.  Trim down the list to something like 4-6 “Core” attributes, which are the “marquee” flavors of the brand.  Additionally, you should develop a list of attributes that are applicable across all your brands; I call these “Standard” attributes, and they are usually things like astringency, carbonation, sweetness, sourness, turbidity, and bitterness.  Lastly, develop a list of potential “Negative” attributes that can potentially arise in your products.  These could be flavors like isovaleric, papery/oxidized, lightstruck, acetic, metallic, etc.  Your particular brand mix and the styles of beers you specialize in will dictate what the Core, Standard, and Negative attributes will be.  For example, a Core attribute for bottled Corona should include lightstruck, while that attribute would be in the Negative category for a Sierra Nevada Pale Ale.  Choose what’s appropriate for your production environment.

The next article will cover flavor profiling, reporting, and data management.  See you then!

The long road to Descriptive Flavor Profiling

What do we have here?  Another Beer Sensory Science article?   Yeah, maybe a few.   I just recently gave a talk about something related to this, so I thought it might make a good subject for a blog article.  It’s a lengthy topic, so I may be breaking it up into multiple entries.   The trick will be posting them all within the same calendar year…

Continue reading

It’s alive!

I’ve just finished relocating to a new city so it seems like a good time to dust off the ol’ blog and create some content!  Let’s pretend that I haven’t left you all hanging for more than a year without any new beer sensory science content and get down to it with a short literature review:

Many brewers and beer aficionados already know that one of the first ways that beer degrades as it ages is by the loss of the hop aromas which are often considered to be marquee flavors in many products and styles.  As such, if one wants to know how to extend the shelf life of beer and maintain a fresh-tasting product for as long as possible some investigation into how these aromas are lost is warranted.

This paper explores the various ways that hop oils (a major source of hop aroma) are lost throughout the shelf life of beer and focuses mostly on the loss of the aromas into packaging materials like the rubbery plastic liners under the bottle caps or crowns.  It was published in the Journal of the American Society of Brewing Chemists in 1988 and written by Val Peacock and Max Deinzer – a former AB chemist and hop guru, and an experienced analytical chemist from the Oregon State University chemistry department, respectively.   Both of these men have been extensively involved in beer research for years, and hop research in particular, so they know their hop chemistry; I can’t think of many too many more researchers more capable of attacking this question.  Let’s see what they have to say about this.

First, the researchers present data from some analyses they performed on commercially-available products:  a “super premium American brand” (Beer 1), a “Central European Import” (Beer 2), and an “American product from a mini-brewery” (Beer 3).  Flavors were extracted from these beers via continuous liquid-liquid extraction with dicholormethane and prepared with 2-octanol as an internal chromatographic standard.  In addition to analyzing the beer itself, they removed the foamed-PVC crown liners and extracted them in hexane prior to being made up for gas chromatography/mass spectrometry analysis.  Relative concentrations of analytes were calculated by finding the ratio of the amount found in the beer vs. the crown liner.  Analytical results for roughly 36 flavor-active compounds (15 from hops) are presented, with concentration values for both the beer and the crown liner indicated.   Overall, they found that the more polar, or less oily, the compound, the less it migrated into crown liners.  Therefore, alcohols and the water-soluble esters (like isoamyl alcohol and isoamyl acetate) were not found in liners in any appreciable levels (0% and 2% found in crown liners, respectively), while the non-polar compounds, like the hop terpenes and sesquiterpenes myrcene and humulene as well as the long-chain fatty acid esters, were found only in the crown liners.  Other hop aromas, like terpene alcohols, linalool, and geraniol, were only found in the beer.

In order to understand the rate of uptake of some of these compounds into the crown liners the researchers created model systems of non-carbonated 3.5% and 3.0% (v/v) ethanol/water solutions and spiked known amounts of several hop-derived compounds, then re-crowned the bottles and stored them for 18 and 28 days, respectively.   In the 18-day 3.5% ABV model, 79-87% of the hop-derived hydrocarbons (myrcene, caryophyllene, and humulene) were lost to the crown liners.  As was seen in the commercial beer analysis very little, if any, of the water-soluble compounds were detected in the crown liners.  In the 3.0% ABV model system after 28 days of storage, the researchers found that only small amounts of the oxygenated hop compounds (alcohols, epoxides, and diepoxides) were captured by the crown liners.  Some of the results ran counter to what was seen in the previous analysis, and it was speculated that either some of the compounds degraded by oxidation after they were captured by the liners, or that the 3.0% uncarbonated model system was different enough from the other beers analyzed and that this unpredictably affected the results.

Finally, the researchers looked at the rate of decomposition of four hop aroma compounds which they had spiked into a “premium American beer” (implied later to not be a pilsner):  linalool, geraniol, humulenol II, and humulene diepoxide A.  Beers  were stored at room temperature for about 60 days to simulate warehouse and market storage.  11% of linalool was lost after 57 days, and the steep-then-level nature of the decomposition curve indicates that the degradation of linalool is not a first-order reaction and implies that there are other factors at play in the decomposition of linalool – either that there is an equilibrium that is reached or that linalool is reacting with beer components that also get depleted over time, such as oxygen.  Breakdown products of linalool were analyzed in the final (57-day) sample and the amounts found only account for 10% of the lost linalool, which is somewhat puzzling – perhaps there are other breakdown products which were not realized in this study.  Geraniol behaved similarly to linalool:  12% lost in 56 days, with the majority lost in the first couple weeks and few anticipated breakdown products detected.  Humulenol II degraded much more rapidly than linalool and geraniol, with 66% being lost after 61 days.  While the decay curve isn’t as “curvy” as the previous compounds, it still leveled off somewhat.  They also found some additional compounds in the final sample which they guessed were humulenol II breakdown products, as there was none of these detected in the fresher samples, nor in the linalool/geraniol samples.  GC-MS results implied that both oxidation and acid-hydrolysis were at play.  Lastly, humulene diepoxide A decayed the fastest of the four compounds, where 84% of it was lost at 56 days in a nearly-linear rate.  Numerous supposed degradation compounds were detected, but the reactions are so complex that identification was not feasible.

Overall, this paper provided an interesting look into a couple of the main reasons that hop aroma is lost in aging beer:   adsorption/absorption into crown liners (and likely aluminum can liner material as well!) and oxidation/acid hydrolysis reactions leading to their conversion to other compounds, both flavor-active and not.  When one considers both the importance of hop aroma to so many craft beers and the fragile nature of hop aroma, it seems like some attention should be paid to maintaining sufficient hop aroma over time.


Fate of Hop Oil Components in Beer. Val E. Peacock and Max L. Deinzer, Department of Agricultural Chemistry, Oregon State University, Corvallis 97331. J. Am. Soc. Brew. Chem. 46:0104, 1988.

ASBC/MBAA meeting was very nice!

The “Brewing Summit” (the joint annual meetings of the ASBC and MBAA) in Chicago just concluded last Saturday and it was a lovely time.   It was the second time I’ve been to Chicago, and this time I was able to bring my spouse along with me and between the seminars, the sightseeing, and the friends/colleagues we saw, we had great fun.  I even got to wear a “Presenter” ribbon on my name tag – a first for me at an annual meeting for these organizations.   Hopefully I’ll get that opportunity again.   Although I didn’t cover the material quite as well as I’d like, I got some great feedback and plenty of compliments, so that was very nice.  That’s normal, though:  I often try to set my standards just out of my reach so I usually wind up a bit disappointed in the result.   It’s hard to feel confident in your material when you’re sharing the stage with some of the Titans of Sensory Science.

I also picked up a brand-new copy of Charlie Bamforth’s new book “Flavor” and got it signed by the Pope of Foam himself.   It’s not a big book, but it’s a great overview of many beer flavor issues, and it’s written in Bamforth’s conversational style so it’s quite entertaining as well.    Another high point was the “Pearls of Wisdom” talk where Oregon State’s Dr. Tom Shellhammer and Firestone Walker’s Matt Brynildson “debated” various hop topics, such as pellets vs. whole cone, Noble vs. American hops, kettle vs. dry-hopping, etc, only to be put in their place with facts from MillerCoors’ master hop chemist Pat Ting.  Very entertaining.  Wish you were there.

Best food I had while I was there?   Breakfast at West Egg Cafe on Fairbanks.   Their omelettes and potatoes were large and delicious, and service was fast, prices were good.

I took over 13 pages of notes for the events I attended, so once I get the electronic proceedings I’ll do some write-ups on the things I saw.   I promise!

Now I just need to dig out of this backlog of work and get this productivity train rolling again.

So, yeah…

…I’m going to put that last topic on the back burner while I reassess how I want to proceed with it.    That post was originally going to look at the claims of a type of household cleaning product we have in our home, but the microbiology data came back confusing and difficult to explain.   I’ll look at redesigning the test and try to get it posted before next year.

I’ve had a heck of a year in this new position.   Developing, installing, and maintaining QC databases, learning VBA and writing macros to manipulate QC and sensory data, making and shipping training standards for our far-flung taste panelists, preparing to move closer to corporate headquarters, managing product specifications, participating in the ASBC Technical Subcommittee on Sensory, and putting out the various fires that come up in our quality labs.

Anyway, the real reason I’m resurrecting this zombie blog today is to mention that I’ll be heading to Chicago next week to attend the American Society of Brewing Chemists and Master Brewers Association of America annual meetings / Brewing Summit. I’ve been asked to present some information during one of the workshops,  so that will be pretty exciting. As of yesterday, there were about 900 people registered for the event in total.   I’ve been to Chicago once before to attend a Siebel class, and it was a relatively nice place.   I like where I live better, but it was nice.

I’ll probably be taking many notes and posting up some of the more interesting things I find, so check back a few times over the next couple weeks and hopefully there will be some new content for you to enjoy!

Now, back to work.   Taste panel is in 45 minutes and I’ve got more data wrangling tools to put in place!

Good news: A new post is coming!

Bad news:   It’s not exactly beer-related.   But is is related to microbiology, food safety, and kitchen sanitation!    And there is a dearth of real information about this specific topic on the web right now so I figured since I can address the topic with original “research”, I’ll put it up here on the blog so others can gain knowledge from it as well.

That’s all I’ll say about that until the results are in.  Expect it in 1-2 weeks, but I have a backpacking trip scheduled for next weekend, so I hope to post it before that.

I’ll also consider what other topics I can post about that are beer-related, as I know I’ve been VERY delinquent in that regard.


Considering new material, and a relevant event announcement

Hello BSS readers,

I know that it’s been awhile since I’ve written, but that should come as no surprise by now.    I have been spending some time recently thinking about how guilty I feel leaving this blog inactive for so long, and considering some material I can post soon.   I’ll do my best to get something up when I can.

Also, I’d like to mention that I’ve received correspondence from a colleague of mine about a beer sensory workshop that he will be running during Seattle Beer Week.    On May 18th at Pyramid Brewery Alehouse in south Seattle, there will be two 90 minute sessions where Ian McLaughlin, of Craft Brew Alliance, will explain sensory science and beer flavor, and will present a number of flavor standards and other types of samples.  It sounds like essentially the same type of material that goes up on this blog, so it could be pretty interesting!

Here is a link to the workshops.  It is $30, but it sounds like that could also get you a free tour of Pyramid Brewery and discounts on food and drink.   And if I can swing it, maybe you’ll even see me there…