I'd like to compile a list of supplies needed for sensory training of our BJCP judges and exam takers.
Does anyone have experience with doctoring beers?
Sorry for the late response to this topic. Here's my experience:
I second Randy Mosher's Radical Brewing as a good source for "improvised" off-flavors.
You don't need to doctor beers to get the point across. Use any handy object which produces the appropriate aroma. It helps if its distinctive or funny so that people remember it. For example, for a session on cider, I wanted to demonstrate to people what "mousy" smelled like. Fortunately, I keep mice. One small plastic bag of used mouse bedding was enough to get the point across. Doesn't have to be mice either, any rodent will do. Anyhow, the people at the session sure remembered the smell!
If you do decide to doctor beers, here's how to do it:
Two weeks before:
Buy a case of relatively cheap, but tasty, beer without extremely strong hop or malt character, so that off flavors stand out. Something like a lightly-hopped blonde ale or a Munich helles is perfect, but a relatively neutral-flavored ale will work as well. I used Saranac Pale Ale because it was local and on discount. I've heard of other people using Budweiser or PBR. Note that doctoring might be obvious in brilliantly clear, light-colored beers.
Gather a horde of small jars so that you can make up off-flavor solutions in advance. You'll need at least 5, and maybe up to 20, depending on how fancy you want to be.
Use a small, reliable syringe or pipette or two to dispense your solutions. Be sure to rinse it off when you switch from one solution to another.
Determine the intensity of your solutions in advance. This will take some trial and error. Use beer poured into 2 oz. sample cups and your syringe/pipette to get the ratios right. Then scale up by a factor of 6 for a 12 oz. can/bottle.
Before the session:
Doctor your beers. Reseal the bottles. Be sure to label them somehow so you know which beer is which. Some might need to be gently shaken to get the doctoring agent into solution.
At the session:
Serve an undoctored bottle of the beer to everyone so they have a base beer to calibrate against.
Bring plenty of dump buckets. You'll need them.
Bring plenty of 2 oz. clear plastic tasting cups, like are typically used for judging.
Your homebrewed flavor kit:
Acetic: White vinegar. The cheap stuff used for cleaning will do.
Acetaldehyde: A) Sour apple candy (e.g., green Jolly Ranchers). Either make a syrup by crushing candy and letting it melt in a sealed jar of distilled water or hand out candies You might have to pick through the bulk candy bin at your local grocery store to get enough, though. B) Sour apple flavor. Available from some baking supply stores. Hard to find, but better than candy. C) Food grade acetaldehyde. Expensive, hard to find. Not recommended.
Alcoholic: Good vodka, from the middle or top shelf.
Astringent: A) Tea boiled in water for 10+ minutes. B) Grape tannin from the winemaking department of your friendly local HB store. It takes a while to dissolve, so let it sit in a sealed jar of distilled water for a few days. C) Rice hulls from your local HB store. Boil those suckers for 20+ minutes to really get the tannins out of them.
Diacetyl: A) Artificial butter flavor, available at most supermarkets or baking supply outlets. The problem is that artificial butter flavor is oily, so it doesn't mix well with beer and kills head, making doctoring obvious. B) Butterscotch candy. Make a syrup as described for Acetaldehyde or hand them out. C) Microwave popcorn - hand the stuff out as munchies. People will get the idea.
Bonus idea: Have people chew on a green Jolly Rancher while also munching a butterscotch candy. Diacetyl and acetaldehyde often go together.
DMS: The juice from a can of corn. Cloudy, so the doctoring is obvious.
Estery: Any artificial fruit flavoring. Banana, cherry, whatever. Easily obtained at the grocery or baking supply store.
Grassy: A) Soak the mankiest, oldest, most lambic-worthy hops you can find in a sealed jar of distilled water for a couple of weeks. B) Fresh grass or plant cuttings allowed to soak in a sealed jar of distilled water in the refrigerator for a couple of days. C) A handful of fresh grass, straw or hay. Hand it around and let people huff it.
Lactic: Food grade lactic acid. Available for adjusting mash pH at your friendly local HB store.
Light-Struck: A) Don't bother. Everyone knows what it smells/tastes like. B) Buy a bottle of green bottle import lager. Let it sunbathe for a few hours.
Metallic: Soak a penny or steel nail in distilled water for a week or so. Maybe throw in a tiny bit of vinegar to hasten the process along.
Musty: A) The juice from a can of canned mushrooms. B) A slurry of blue cheese and distilled water. Let it sit for a couple of days so that the cheese chunks settle. Both options might be cloudy, making doctoring obvious.
Oxidized: A) Leave a bottle of beer in the trunk of your car for a few days during the summer. Let your car sit out in the sun so it gets really hot inside. B) Open a bottle of the beer a couple of days before the session. Pour it roughly from glass to glass. Pour it back into the bottle. Recap the bottle and let it stand at room temperature. You might get some lactic or acetic sour as well! C) Take cardboard or paper, like paper towels or the tube inside the roll. Shred it. Let it soak in a sealed container of distilled water for a couple of days. The liquid can be added to beer with minimal ill effects, other than a desire to not drink more than a sip of beer. Alternately, just let people smell the contents of the jar. D) Go to a beer store infamous for treating its products poorly. Choose the dustiest, cruftiest-looking bottle of low alcohol (below 5% ABV) beer you can find. Look for products no longer being made, from breweries that have long vanished, in countries that no longer exist. Oxidized character can be very different in light-colored vs. dark beers, so if you're really into the topic, you might buy several brands of brutally abused beer for comparison. E) Sherry or sherry flavor. Good for getting the notes associated with strong aged dark beer.
Phenolic: A) Smoke flavoring. Be careful with it, a little goes a very long way. B) Chloraseptic mouth rinse, original flavor Listerine or their equivalents. Again, a little goes a very long way.
Sour: See Acetic or Lactic.
Solventy: A) Cheap vodka. The bottom shelf stuff in a plastic jug, which is normally served al fresco
from a brown paper bag. You can use the rest for airlock filler/sanitizer. B) The heads/tails from your friendly local distiller's latest batch. Be careful, though, not only are they very volatile, they're also poisonous if consumed in any quantity. C) Nail polish remover - BUT ONLY TO SMELL, NOT TASTE!
Sulfury: A) Soak matches in a sealed jar of distilled water for a week or so. BUT ONLY TO SMELL, NOT TASTE! B) Buy asafetida at your local Indian or health food store. Let it soak in a sealed jar of distilled water for a couple of days.
Vegetal: A) The juice from boiled cabbage. B) The juice from just about any canned vegetable: asparagus, baby onions, whatever. These might be cloudy, making doctoring obvious.
Yeasty: A) Fresh yeast slurry off the bottom of your primary fermenter. B) Brewers yeast from from a health food store - crushed and soaked in distilled water for a few days. C) Vitamin B pill - crushed and soaked in distilled water for a few days. D) Marmite - sold wherever the Queen's English is spoken. E) Vegemite - sold wherever Strine is spoken. In the latter two cases, beware the saltiness that goes with the yeastiness.