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.

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…

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Overall Difference Tests

Let’s change tack a little bit here and discuss a specific set of sensory tests: overall difference tests.

Deciding whether two samples of beer are different is not as easy as it may seem. Everyone perceives their senses slightly different than others, so what one person may find to be a noticeable difference may only be detected by few, if any, others. Various types of bias may also lead people to find differences that don’t exist. On top of this, the need for accuracy in your data means that you often need more than just a few people to be able to truly say whether there is a difference. So, as with all laboratory procedures, there are standardized methods and tests that are used when searching for differences in food and beverage systems. Even under the heading of “overall difference tests” there are a number of different tests that can be used, each with their own pros and cons.

Overall difference tests are used to find whether there is any detectable difference between two samples. Where exactly that difference originates is not necessarily part of the goal of the difference test, although you can usually pull out some hints to help guide your progress. This type of test differs from the more specific “attribute difference test” which seeks to determine whether a difference exists on the basis of one specific aspect of the sample, whether it is the color, the bitterness, the phenolic aroma, etc. I’ll discuss attribute difference tests later, but before we move on to the tests themselves, a word about error first.

In statistical tests such as these, there are essentially two types of error: α-error, and β-error. α-error is a numerical representation of the risk you are willing to accept for the possibility of finding a false-positive, or finding a difference when one doesn’t exist.  β-error is the same type of numerical representation, but it signifies the risk you accept for possibly finding a false negative, or missing a real difference that exists between the samples. In practical situations, you must balance which risk you want to minimize over the other, since minimizing both requires many more panelists and samples than most production environments can accommodate. For overall difference tests it is usually the alpha that is minimized, while the β-risk is allowed to be large to keep the number of assessors reasonable. The default value for α is usually 0.05 meaning you, as the administrator, are accepting the possibility that there is a 1/20 chance that the results will indicate a difference when one doesn’t actually exist. An α of 0.05 isn’t required by any means, but it usually offers a good balance between risk-management and panel size.

What follows is a breakdown of a few of the more commonly used types of tests that can be used to find an overall difference between test samples.

Brewing Technology Blog

I was just going through some of the links that have been sending traffic to my blog, and I noticed one of them was from a Tweet that Bill Simpson (from CaraTechnologies) made awhile back, calling it a “great blog about beer tasting”; awesome! Although he may not recall it, I’ve met Bill Simpson before and he is quite knowledgeable about beer and brewing. I suppose you’d have to be if you were a consultant for any number of brewing-related issues. Anyway, he’s sent some traffic my way, so I’ll send some to him. His blog is The Brewing Technology Blog and has lots of great information. Now, I’m telling you this in confidence that you won’t run off to some other blog and forget about this one. Fortunately, he seems to update his blog slightly less often than I do, but he also covers a broader range of topics than I do, too.

At any rate, check it out. It may be more suited for commercial brewers than homebrewers or beer drinkers, but there is information there that can be used by anyone.

Can’t find the beer you want? Trade for it.

Many of you readers are already Redditors so some of you are already aware of this system, but I certainly think it’s worth mentioning for the people who don’t know about it.

Reddit.com is a unique on-line community which is essentially a user-driven news aggregator. Various types of links are constantly being submitted to the site, and they are voted on by the community as to their worth. The highest voted articles get to the front page for maximum visibility. The submissions can range from breaking headlines, to personal stories about tragedy or triumph, to the ubiquitous “lolcats” pictures. Fortunately, Reddit supplies the capability to subscribe to certain “subreddits” (hundreds of them) in which the various types of submissions are categorized, so you can usually filter out the stuff you don’t want to see. It’s a great community with an active and fervent user-base. Best of all, it’s free.

Anyway, they have a subreddit specifically for trading beer. If there is something that you enjoy but can’t find in your area, you can probably find someone who is able to locate it and is willing to trade you for something. Check the rules and guidelines for the various restrictions and procedures that are in place.

So go forth and create! … a user account so you can get that beer you haven’t been able to find since your trip to that other state or country. Also, while you’re there, check out r/SnackExchange (same principal), and r/homebrewing, and r/beer, where lots of discussions take place about those topics.

Looks like someone beat me to it: how to find fresh beer.

I wrote a post last week asking for requests for production information on beer labels, in an effort to accumulate a database that you can reference in your quest to buy fresh beer.

Well, one commenter has enlightened me to the fact that this has pretty much already been done.  What a load off my back!  This could have been a huge and on-going project, and I’m a bit relieved that I don’t have to assemble and maintain such a list.

I’ve had a look over it and it’s huge, and from the entries I’ve seen, pretty accurate too.  Of course, breweries change their labels and equipment all the time, so there may be some inaccuracies hiding in there somewhere, but it’s a great start.

Fresh Beer Only.

So, find your favorite breweries in this list, and make a note of where and how they put their information on the label (hopefully they put something on there; there’s a disturbingly high number of packages that have no information whatsoever on them). Then when you’re standing in front of the beer aisle at the store, don’t be afraid to shuffle the bottles around in order to find the freshest. You deserve it.

Bias: How easily we’re fooled.

In sensory science, we deal directly with extracting information from tricky and fickle systems:  humans which, as we know, are animals with brains just advanced enough to get them into trouble.  Particularly, we focus on what the subjects are experiencing from a sensorial standpoint and that, on its own, is a system which is easily confounded. This article is about the things that fool us:  the phenomena that occur around us which influence us and how we perceive reality.  It’s rather startling just how easily we can be tricked and even manipulated, and there are long and growing lists which detail our understanding of the “failures” which can be triggered in our sensory systems.  Of course these are general tendencies and not concrete rules that every human unknowingly follows.  But bias is a clear and present threat to the validity of all sensory data, and care and vigilance must be exercised by panel administrators in order to mitigate its effects.

First, we’ll discuss some of the more general ways that humans can be fooled, some of which you’ve probably seen before, then we’ll move into how it directly affects a sensory panel and even the average beer taster.

Probably one of the most famous examples of these failures of the human brain’s perception abilities is the selective attention test by Daniel Simons and Christopher Chabris from 1999. Basically the video shows you a small group of people passing basketballs back and forth and asks you to count how many times the balls are passed. If you haven’t seen it, follow that link and watch it. It’s only a minute or so long, I’ll wait here. — Great, did you see the gorilla? At one point in the video someone in a gorilla suit walks across the screen, right through the basketball game. The point of the exercise is, if you’re so attentive to the basketballs you can miss something which is right in front of you, even if it is quite absurd and out of place. It’s probably so famous that it’s hard to fall for it anymore, but it is a well documented experience.

Help Me Help You Find Fresh Beer

I’ve already mentioned, buying fresh beer is very important to me, and it should be for you. The problem is it’s so hard to find out whether the beer in front of you at the grocery store is fresh. Some breweries don’t label their beer with any production information, some put it in hard to find locations, some use a format which defies decoding, and some use a “Best By” date rather than a “Born On” date (which makes it difficult to tell how old the beer is since you don’t know what the brewery considers their beer’s shelf-life to be).

So what I propose, and it just may be a bit daft to try, is for us (you and I) to attempt to compile a collection of label information for various breweries. If we can get enough information gathered together, maybe people can start to find the fresh beer that they deserve. Of course, just because the label says it’s a young and fresh beer doesn’t mean it hasn’t been abused.  It doesn’t take long for elevated temperatures to adversely affect beer flavor; just a few days in the trunk of your car in summer is enough to trash something like a lager or pale ale (something like a stout or imperial IPA might hold up a bit longer).

More after the break…

Jackpot! The Beer Fishbone Diagram

This PDF is a bonanza of information, enumerating the multitude of factors involved in all sorts of beer phenomena. It’s called a Fishbone Diagram, and the reason is obvious once you see it. I can’t even begin to explain everything that’s in here, I mean it would takes hours (days?) to pick it apart.

It’s pretty easy to interpret, although it is a bit of an information overload. Each page explains the various factors that influence a particular quality issue in beer. For example, below is a screenshot for the one of the pages [!] about how packaging and brewing issues interact to promote or limit beer oxidation. Other issues covered are controlling beer pH, fusel alcohols, H2S levels, foam quality, beer stability, yeast flocculation/vitality/viability, etc etc etc.

Brewing/Packaging Parameters and Beer Oxidation

You can find it here:
[see below]

Please excuse the rotated table of contents; I rotated the PDF so that the first page was the only one (of 42) that you needed to crane your neck to read. Better yet, print it out and enjoy it with a pint or two of your favorite beer. I’m going to go get a blonde ale out of the fridge right now.

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Edit, 1/6/11:  Looks like these fishbone diagrams were developed by Greg Casey, recently (currently?) of Coors Brewing.  I hope it’s OK that they’re posted here…

Edit, 1/2/13: I’ve recently been informed that the file on the host site disappeared, so I’ve rehosted it at another site. If it disappears again, shoot me an email and I’ll try to get it back up.

Edit, 1/23/13:  At the moment, the free file-hosting websites I’ve been using don’t seem to have much of a shelf-life.   Either that or Greg Casey has a Google Alert on “beer fishbone diagram” and every time he sees the file posted he submits a takedown request to the hosting site.

Anyway,  I’m going to do this on an on-demand basis.   If you’d like a copy of the Beer Fishbone Diagrams, email me (found on “About” page) and I’ll get you a copy within a couple days.  

The HopUnion Variety Book

One thing no homebrewer should be without is the Hop Variety Book (PDF) from our friends at HopUnion in Yakima, Washington. This wonderful book has information for dozens of domestic international hop varieties, including their alpha acid, beta acid, and essential oil content, and so much more including some decent aroma descriptors as well.