1. Common Off Flavor Training
Tommy Yancone-Technical Brewer

2. Overview Welcome & Introductions Purpose of training Guided tasting
Off flavor discussion (What? Why? How?)
Tiffany Pitra: Hop Sensory Coordinator
Tommy Yancone: Technical Brewer
Adam Moses: Regional Sales Manager, North East
Steve Thompson: Regional Sales Manger, Central
Unfortunately, we’ve all tasted bad beer, but we may not necessarily know why it’s bad, or how to describe what the awful flavor we’re experiencing. At Yakima Chief, we train all of our in-house sensory panelists on off flavors so they can identify when something has gone wrong.
The purpose of today’s training is to familiarize yourself with 6 common off flavors found in beer. At the end of our time today, you should walk away with a term and definition for each off flavor, along with a deeper understanding of why these occur and how to avoid them. You’ll also be able to experience each off flavor by smelling and tasting the samples in front of you. You’re welcome!

3. How to optimize your training experience
Directions:
Taste the control sample
Taste the test sample as directed by the instructor
Reveal and discuss the off flavor
Record the sample number in the correct off flavor box
We are tasting Sam ‘76 dosed with standards at ~6x threshold
You have 6 test samples and one control. Each sample has a 3-digit code. As a group, we’re going to taste one sample at a time. Please don’t jump ahead! This is an interactive group training session, and the conversation will flow much more smoothly if we taste at the same pace.
After you’ve tasted the sample, we’ll reveal what the off-flavor is. It’s up to you to write the sample number in the correct off-flavor box. We’ll discuss the off flavor in greater detail—what causes each one and how to eliminate them from your beer. Feel free to take notes on the placemat and take it with you when you leave.
Start by tasting the control sample. You may retaste this sample for reference. Raise your hand throughout the session if you require more control beer, and we’ll refill your glass.
As you taste the test samples, you may have trouble smelling some. It can help to cover the glass and gently swirl the sample. Remove your hand and sniff the sample. There is also a chance you may be less sensitive or blind to some of the off notes.

4. Taste Sample #283

5. Diacetyl (2,3 Butanedione)-283
Aroma & Flavor-Artificial butter or butterscotch, slick mouthfeel in high concentrations
Rarely a desirable compound
Sometimes referred to as “VDK” along with 2,3 Pentanedione
Natural part of the fermentation process
Can be a very common off flavor in beer
Has a very low odor threshold
α-acetolactate
Diacetyl
2,3 Butanediol
oxidation
Time
Yeast
No aroma
Butter
No aroma
Like all off flavors, it can be harder to pick up in more heavily flavored beers (whether by hops or adjuncts)
α-acetolactate is an intermediary step during the formation of valine by the yeast cells. Usually there is an overabundance of α-acetolactate produced, and some of it will escape outside the cell. Once there, it oxidizes and becomes diacetyl. If given enough time at normal fermentation temperatures, the yeast will absorb the diacetyl and convert it into 2,3 butandiol, which doesn’t effect the flavor of the beer.
If yeast cleans it up naturally, where’s the issue? Since α-acetolactate is odorless, it can make its way into your final beer. If this happens, it will eventually oxidize into diacetyl
How to protect yourself:
1-Test for diacetyl
-after dry hopping, take a small sample ~100mL and put it in a covered container shake and vent 3 times to remove some of the carbonation
-place in a water bath at about 135F for 45 minutes to an hour
-take it out of the water and let it cool to room temp
-smell and taste the sample-it will taste weird, because it is warm, but you should hopefully be able to pick out any sort of butter flavors/aromas
-if you do taste something, let the fermentation ride, and check again in a day or two. Eventually the yeast will reabsorb it
-if you don’t taste anything, you can continue processing without fear of diacetyl
2-Bottle conditioning
-luckily for those of you who bottle condition, the small amount of yeast leftover in the bottles will hopefully clean up any leftover α-acetolactate in the bottle (as well as the tiny amount made by fermenting the priming sugar)
Another common source of diacetyl is from contamination, usually in draught lines. Beer spoiling bacteria can produce diacetyl and it can ruin an otherwise diacetyl-free beer.
Its very important for those of you who keg to clean your lines reguarly
hop creep

6. Taste Sample #770

7. Acetaldehyde-770 Aroma & Flavor-Solvent/Green Apple/Squash
Usually a yeast based off flavor
Precursor in the conversion of glucose to ethanol
High acetaldehyde levels indicate either an incomplete fermentation, or unhealthy yeast
Make sure you are pitching enough yeast, make a starter if necessary
Glycolysis
Yeast
Yeast
Glucose
Pyruvate
Acetaldehyde
Ethanol

8. Taste Sample #965

9. Dimethyl sulfide (DMS)-965
Aroma & Flavor-Cooked or creamed corn or cooked vegetables
Very low threshold
Is usually present in all beers at some point
S-methylmethionine, which is present in barley gets converted into DMS during the malting process
Kilning for longer, or roasting at higher temperatures will reduce the amount of SMM present in the malt
Its low boiling point (~100F) makes it easy to volatilize DMS by boiling
Yeast
Heat
S-Methylmethionine
Dimethyl Sulfide
(DMS)
Dimethyl sulfoxide (DMSO)
homoserine
Dimethyl sulfide, or DMS as its usually referred to is a very common off flavor in craft beer.
It has a creamed or canned corn flavor, sometimes getting more vegetal
Its not a desired compound in beer
Since it is a sulfur containing compound it has a very low odor threshold for humans, however, in my experience it is a compound that many people are blind to
Production and Removal
During the malting process, s-methyl methionine, which is present in barley, begins to be converted to DMS this happens above about 80C/175F
Malts that are kilned or roasted for longer will have less residual SMM, therefore lightly kilned malts will have the highest levels of SMM
Some of this DMS as well as unconverted SMM gets transferred into the wort during mashing, where the SMM will continue to convert to DMS as it is heated
Luckily DMS is easy to get rid of. It’s boiling point is around 100F, so during the boil it will volatilize, as long as your kettle is uncovered, and you have a vigorous boil for at least 60 minutes
More SMM can be converted throughout the boil, but that small amount of DMS that is produced should be scrubbed out by the CO2 bubbles
Some yeasts can convert SMM’s other byproduct DMSO into DMS as well
half life of SMM is 38 min at 100C
homoserine is an α-amino acid

10. Taste Sample #521

11. Oxidation-521 Aroma & Flavor-Sweet, paper, cardboard, sherry
Produced when beer is exposed to oxygen
The rate of oxidation is determined by oxygen level, temperature, hopping level, and time
There is no way to produce a 0ppb O2 beer
Bottle conditioning can help, since yeast will clean up most of the oxygen at packaging
Make sure you purge your kegs completely
This beer is only a few weeks old, but has been sitting in a hot car for 5 days
keg purging method
splash as little as possible if not kegging

12. Taste Sample #448

13. Isovaleric acid-448 Aroma & Flavor-Cheesy, parmesan, sweaty
Usually derived from hops
Isovaleric acid is produced during the oxidation of alpha acids in hops
This can be caused by poor processing methods, or improper storage
Can also be derived from Brettanomyces strains
IVA is desirable in aged hops
fermentation + aging
isovaleric acid
ethyl isovalerate
processing
storage conditions
brett can be on purpose or contamination

14. Taste Sample #191

15. Lactic acid-191 Aroma-Usually not present, unless in high quantities
Flavor-Clean sour
Desired in sour beers, but an off flavor in other styles
Less flavorful than other acids such as acetic or butyric
Lactic acid is produced by lactic acid bacteria which are used in yogurt and other fermented foods
LAB is relatively easy to kill with sanitizer or heat, but if cold side equipment isn’t sanitized properly
The low pH/alcoholic/hoppy nature of beer will help prevent infection by LAB, but it is still possible

16. Any Questions?
Thank You to the Yakima Chief Hops employees who volunteered to make this session a success:
Tiffany Pitra Bri Valencourt Megan Yusi Jaryl Pence
Kristin Lindsey Wade Brummett Victoria Garza Kayla Thomas
Thank you for attending today’s training!
We would like to thank Aroxa, Yakima Chief Hops Marketing Team and all the employees who volunteered to help execute this session.