The Pellicle Brief

The Pellicle Brief

©2018  Ross Williams

I brew my own beer.  As a result, I get better beer for the money I spend.  Of course, it takes time, effort and a basement that hangs out in the mid to upper 60s.  Luckily, I have all three.  I can get 36 pints of an excellent Russian Imperial Stout for the cost of four pints at a local beer hall, or six at the liquor mega-store.

At this point I don’t even count the cost of the equipment in the equation.  Those costs have long ago depreciated to nothing.

The hobby started a few years back.  I told my wife that if she wanted to get me a Valentine’s Day present guaranteed to please, make it a brewing kit.  I’d watched Alton Brown’s Good Eats show where he demonstrated cooking a beer and figured if the Egyptians could do it without knowing a damn about biology or chemistry, I − a high school science geek − could do at least as well.  Seemed simple enough.

And honestly, it is.  I don’t go getting all pedantic about it.  I just sample commercial microbrews for styles I haven’t had.  If I like the beer I buy a similar beer kit.  Then I cook it, and struggle with the bucket down the basement steps.  The one major problem with making my own beer is carrying five gallons at a time up and down a staircase after having had spinal surgery.

At this point in my life, I’m content letting the beer geeks do all coping with the alphas and lovibond scales.  When they finish geeking out and get a recipe they’re happy with, I’ll buy it − or not − and compliment or criticize the result.

The only issues I have are relatively minor.  I mostly address them by ignoring them.  I encountered one issue multiple times, however, and decided that I wanted to find out more about it.  Every six or eight batches of beer, I’d notice patches of dry, powdery schmutz on the surface of the beer when I opened the fermenting bucket.

I did a quick google − nothing.  So I went to the dot-com I buy my beer kits from to talk with their beer geeks.  Surely they’d know.  They didn’t.  The beer geek I talked to kept trying to tell me that the white powdery patches on top of my ferment was soap powder − I had mentioned that sometimes I clean my beer buckets with soap.  I use cheap liquid dish soap, the kind which, for what it’s worth, doesn’t leave a powdery residue.

When I reminded the beer geek that this happened whether I cleaned my equipment with soap or not, he changed his answer to a chemical reaction between an ingredient in the beer and the chlorine bleach I sometimes use [at Alton Brown’s suggestion] to sanitize my equipment.  When I reminded him that this happened whether I soaked in a mild chlorine solution or not, he changed his answer yet again.

 
In short, he had no clue.  But I was still scolded about not buying one of the expensive chemical “food-safe” sanitizing compounds they sell on their website which absolutely, positively do not alter the taste of beer.  …they claim.

Thanks, no, I’m good not indulging a fallback into gratuitous chemical additive.  The beer I made tasted fine whether I ignored small amounts of this schmutz, or skimmed off the larger patches.

Still, unsatisfied with the Beer Geek Solution, I googled some more.  Finally, after about the twentieth combination of search terms [which I cannot duplicate to this day to find again what I found before], I happened across a scientific blog entry made by a guy with a PhD in microbiology who also brews his own.  His scientific essay was upon the formation of pellicle.

Pellicle is, essentially, an “extracellular extrusion” [i.e., microbiological poop] made by single-celled organisms such as the yeast which ferments the monosaccharides in a cooked beer.  These extrusions are sticky and tend to form chains.  Enough chains make a web-like structure.  When these form on the top of a liquid − such as fermented beer in a bucket − they will trap tiny gas bubbles and rise to the surface, giving the liquid the appearance of a [comparatively] dry, powdery film.

Furthermore, all single-celled organisms − yeast, algae, mold, bacteria, etc − have the gene to make pellicle.  But the yeast used for brewing have been selected in the hundreds of years of formal brewing, and the millions of generations of yeast those hundreds of years entailed, for the mutation which turned off the activity of that gene.  The microbiologist identified, by name, the gene in question.

Commercial brewing yeasts are sold from the stock having this pellicle-free mutation.  Yet mutations, being what they are, remutations can and do occur which turn this gene back on in commercial brewer’s yeast.  The result is pellicle formation on top of a fermented beer.

This happens in commercial breweries as well.  When it does, the batch of beer, all million gallons of it, is discarded.  The batch is considered “contaminated”.  The yeast stock, which the brewery’s yeast department cultivates, is tested.  If the mutation is in the source stock of yeast rather than occurring in the yeast growing in the vat, the yeast is also discarded and a prior generation of yeast replaces it.

When this happens in homebrew, the natural inclination is to say “Eww!”  No one wants to drink fuzzy beer.  Homebrew suppliers are only more than happy to enable this contamination line of thought by selling another kit, or guilting the homebrewer into dousing brewing equipment in a chemical bath … witness my conversation with the dot-com’s beer geek.  This wouldn’t stop pellicle formation in any event.

The microbiologist concluded his essay by saying that you can throw away your fuzzy beer if you like, but it’s probably unnecessary.  Your beer is most likely perfectly fine and no one will know the difference.

Knowing that the substance is called pellicle, I googled some more.   What I found − and what all beer geeks working for homebrew dot-coms should know without having a novice explain it to them − is that white pellicle is from yeast or other benign organisms − like lactobacillus.  If you see white pellicle on your beer, it’s either from the commercial yeast you pitched having lost the non-pellicle mutation, or a ubiquitous wild yeast that migrated in before you closed your bucket, or a ubiquitous and wild lactobacillus.  Lactobacillus is sold in pill form as probiotics and, in combination with wild yeast, makes sourdough bread so uniquely delicious.  White pellicle may appear beige to light brown if the beer you’re fermenting is an amber or a stout.

Green pellicle is bread mold.  Unless you or your beer drinking guests have an allergy to penicillin you’re going to be fine.  But I would still dump the beer.

It is black or red/pink pellicle that is a true contaminant.  It can be anything from common shower mildew to something far, far worse.  Seeing these would inspire me to wash my equipment with soap, then soak in a high chlorine solution, and then wash with soap again.  And maybe once more.  Even then, I might just go buy new fermenting buckets and start the whole depreciation game from scratch.

Ignoring issues has limitations.

Now, if you’ll excuse me, I have a pint of excellent Russian Imperial calling my name.  It cost $1.25/pint to make.  I can stand a little fuzz.