Sophic Suds

A beer-colored, sepia-tone-like picture of glass of beer overlooking a valley
(Image: “When Beer Ruled the Earth” – you should really click through and read the caption that goes with it…)

A fundamental aspect of my personal philosophy is this: If you cannot play with something, you have not mastered it, and if you do not play with it, you will not master it.

I can sit here and read for hours, but it’s time I actually put my hands on some brewing again. I have a pound each of wheat and amber dried malt extract, an ounce of a low-bitterness (~2.9% alpha-acids) pellet hops, a packet of medium-attenuation dried beer yeast, two 39 millihogshead plastic containers that I can use as fermenters, an early-20th-century hand-cranked blower/bellows, a hot glue gun, a gallon of pineapple juice, some air-line tubing, a cabinet full of spices (including, of course, ginger), at least one small room air-filter, several pounds of honey, perhaps half a cup of granular erythritol, glycerol, a whole mess of glass bottles and bottlecaps, a variety of high-caffeine black tea bags, miscellaneous kitchen implements, a couple of copper-coated scouring pads, a selection of two-liter PETE bottles, iodophor concentrate, a hydrometer, a somewhat overstressed and twisted mind, a wife, four cats, and a dog. What shall I make?

I’m thinking I should aim for a mildly sweet brew with a ginger bite, perhaps adding a bit of tea or pepper if the sweetness needs balancing – but of course part of the goal of the exercise here will be to try to adapt to whatever I’m getting along the way…

Suggestions?

The rightful place of science, and “The definition of an intoxicating beverage”

Advocates for the repeal of prohibition carrying 'We Want Beer' signs

Just a brief point first: President Obama in his inaugural address promised to “restore science to its rightful place.” In traditional fashion, this prompted all manner of verbosity on blogs around the web concerning just what science’s rightful place actually is. Let me just take a moment to settle this question:

Science’s rightful place is kneeling at my feet in supplication and doing my bidding! AH, HA HA HA HA HA!!!!!

But that’s not what I came here to post about. Instead, I wanted to mention a paper I finally got my hands on. You may recall that some time back there were a few stories that popped up about what was said to be a “you can’t get drunk on beer” paper published back in the 1950’s. As usual, the people doing the reporting couldn’t be bothered to actually cite the paper in question, but I figured out which one it was. The paper is this one:
Greenberg LA:”The Definition of an Intoxicating Beverage”; Q J Stud Alcohol. 1955 Jun;16(2):316-25.

I have that paper. And I am quite disappointed in it in much the same way I was with Linus Pauling’s paper proposing a triple-helix structure for DNA. I did, though, learn some interesting things from Greenberg’s paper.

It turns out that the paper actually concerns the legal definition of “intoxication” and whether or not, based on this definition, beer should be classified as an “intoxicating beverage”. Greenberg actually raises some good points…but first, some amusement:

“The average alcohol content of American beers is 3.7 per cent[…]The strongest ale is 4.2 per cent” (page 320, paragraph 4)

Unfortunately, this isn’t quite as funny as it sounds, because the part I clipped out of that quote is where he says “by weight”. It’s still kinda funny though, since that would mean, in mass-market-bladderwash terms, that “The Strongest Ale” is Heineken.


This Alcohol-by-Weight-vs-Volume issue may actually be part of why American beers have a reputation for having watery, feeble beers. It evidently used to be that places like Canada were using alcohol-by-volume, while the US was using alcohol-by-weight on their labels. An otherwise-identical beer bottled in Canada would have a higher “percent alcohol” on the label than the US-bottled version, making it seem as though the American version was weaker. So, evidently it’s not really true…things like “Coors Lite” notwithstanding. (See this recent page at Fermentarium.com for more details.)

But back to the point of the paper…evidently as Greenberg was writing this paper half a century ago, there wasn’t a clear, quantitative scientific or legal definition for “intoxication”. He points out that you can’t just define it in terms of alcohol merely having noticeable effects on the drinker, since the magnitude of the unpleasant effects at low to moderate drinking levels aren’t really much different than that for (for undesirable effects) lack of sleep, distraction [remember all those studies saying talking on the cell-phone while driving is as bad as being drunk?], hunger and so forth. For that matter, I think we can all see the problem of trying to arrest anyone who is being relaxed and amiable for “public intoxication”.

Greenberg solves this problem by looking at the average blood-alcohol concentration of people arrested for “intoxication” (0.21% back in the 1950’s, evidently), and a couple of previous studies from the 1920’s and 1930’s, and he finally settles on 0.15% Blood Alcohol Concentration as a level he’ll use as the line for “definitely intoxicated”. He then proceeds to go through the common classes of alcohol-containing beverages to determine how easy it is for someone to consume enough to reach this BAC.

In summary – For hard liquor, and average person would have to consume 8 ounces plus one ounce per hour of drinking (for example, 9 ounces consumed over the course of one hour). That’s not a difficult quantity to fit into a typical stomach, so hard liquor is obviously an “intoxicating beverage”. Fortified wines (like Port, Madiera…or Thunderbird): about 18 ounces plus 2 ounces per hour – say, a pint and a half in about 4 hours. Still pretty easy to do. An ordinary wine (like, say, a Gewürtztraminer): 36 ounces plus 4 ounces/hour – or a 7-11 “Super Big Gulp®”-sized portion in two or three hours. Getting to be a fairly substantial amount of liquid, but still plausible.

And then there’s beer. Greenberg comes up with a figure of 80 ounces + 10 ounces/hour. That’s roughly three quarts within one hour, which is quite a bit more than the approximately 2 quarts that a human stomach can hold. He goes on to describe several controlled experiments on beer consumption and the resulting blood-alcohol concentration. By pushing one group to consume a gallon and a half of beer over a period of 8 hours, they were able to get up to an average of just under “intoxicated” (by Greenberg’s definition) at 0.13%. The rate of beer ingestion required to pass the “intoxication” threshhold was more than most test subjects could even manage. Therefore (Greenberg concludes) beer should probably not actually be classified as an “intoxicating beverage”

Now for the party-poopery: Greenberg explicitly points out that this is certainly not the same as saying that beer cannot impair a drinker’s performance or judgement, so just because you haven’t consumed anything stronger than beer it doesn’t mean you should be allowed behind the wheel of a steamroller. Nor does it mean that it’d be okay for an alcoholic to drink beer (since an alcoholic is very unlikely to stop with just beer). Furthermore, these days “intoxicated” is legally about half of the level that Greenberg is using – 0.08% in most places in the US as far as I can tell. By Greenberg’s measure, you can easily get that amount of alcohol out of a pitcher of beer consumed over an hour.

So, Greenberg isn’t crazy, and beer can still make you drunk, just as we all would expect. How disappointing. Still, it’s an interesting paper and I’m glad I dug it up.

On a related note, if I can get my hands on an old paper from the Journal of the Institute of Brewing, I may have found my selection for February’s Giant’s Shoulders blog carnival. Stay tuned, more to come…

Exhaustipated, but I’m home

I had to forgo the pleasures of lounging in the hotsprings, due to the excess of time it took to load up Flagella for the trip back and finish running errands. I had to get out of Idaho while the getting was good, as another storm was on the way. Still, the return trip wasn’t a total loss:

FloppyCow gazes from inside Flagella (my car) at the beer I just picked up at New Belgium Brewing Company - La Folie and Frambozen
I managed to score a couple of bottles of La Folie and a six-pack of Frambozen. FloppyCow is jealous. These brews may make a decent relaxative with which to treat my exhaustipation.

I learned a few things playing with my prototype “Where Was I? application for Asterisk. For one thing, I need a longer greeting message, so that my asterisk box will still be listening when my cellphone finally obeys me mashing on its keypad and sends the tones. For another, Suddenlink may be screwing me over on my outgoing data (I’m supposed to be getting 384k outgoing, which ought to be plenty of bandwidth, but strangely enough from outside my VOIP packets are getting completely screwed up. I need to research this to see if it’s really them.) In any case, I had fun playing with it, and now have a better idea of how to (re-)design it for regular use.

Meanwhile, though, now that the car is finally unloaded again it’s time to rest and try to remember everything else I needed/wanted to get done during the holiday break.

Oh boy. This is “bad”.

(Note the “scare quotes” around “bad” up there…)I woke up kind of late this morning, which is probably just as well as I think I really needed the sleep before I load up the car with stuff from the old house and make the ~1600 mile (about 2575km or 83.45 picoparsecs) return journey. As a bribe to myself for making this trip, there are two places I had been considering stopping for a bit on the way back. One of those two is New Belgium Brewing Company in Fort Collins, Colorado. In order to do this, though, I obviously need to arrange to be going through Fort Collins (around 8-9 hours from here) while they’re open. The thing is, there’s really not much point in stopping from my perspective unless they happen to have what I’m really interested in – their not-always-available limited-release “La Folie” (link from the image goes to the page describing it) and possibly their seasonal “Frambozen“. Last time I went by it appeared they always had some La Folie on tap at the tasting counter but not in bottles for take-out.

It turns out New Belgium is open on Saturday until 6pm. And they have both La Folie and Frambozen in bottles there right now.

The other possible stop is Lava Hot Springs, Idaho, where I find it very enjoyable to lounge in the hot springs amid all the snow. However, they open at 9am, so even if I get up really early to make it to Fort Collins before New Belgium closes, I can’t spend any time in the hot springs until 9am anyway, so I’d never make it from the Hot Springs to Fort Collins on the same day. I could, of course, lounge at the hot spring today and then hit Fort Collins tomorrow morning, stopping somewhere between Central Wyoming and Fort Collins tonight, but that could mean the return journey spanning three days rather than two.

However, the weather on this side of Idaho and Wyoming looks most passable today especially later in the afternoon when the roads have been cleared off well, and it looks like getting across the bad wind and snow on the Eastern side of the Wyoming may be safer and better tomorrow morning rather than today.

So, basically, the entire Universe (or at least that portion of it in charge of weather for this region of the country) is obviously telling me that I should take my time loading up and getting out of town, and then go ahead and stop at Lava Hot Springs for a little while to relax before continuing on to somewhere around Rawlins or so, and then resume in the morning which should just coincidentally put me going through Fort Collins in the Late-Morning to Early Afternoon time frame, when New Belgium Brewing is open.

I mean, I don’t want to stop and enjoy myself. Really, I want to be a good boy and drive back in the quickest, most efficient way possible, but who am I to thwart what is the Obvious Will of the Universe? (Supernaturalism makes some of the best excuses…)

In other news, I did manage to fix the Stupid Mistake™ in my little “Where Was I?” application for Asterisk, so now not only do the location updates happen but also the conversion of the associated voice update to MP3 for listening now happens automagically as well. I also fixed the hard time-limit, so updates shouldn’t cut off at 30 seconds like the one from Fort Collins did on the 24th. If you keep an eye on the page and everything goes well for me, you may catch an update from Lava Hot Springs later in the day. If you are especially bored (or are being paid by a Secret Government Agency or Vast International Conspiracy or Santa Claus to spy on me) I will try to do an update from there while sitting on the steps in view of the East Webcam. If so, I’ll be the tiny figure waving at the camera from the steps. If you happen to be watching at the right time, you might catch me there to gaze upon my magnificent pixellated spiffitude. Just don’t look directly at it or you may go blind…

Naturally, a live update from New Belgium Brewing Company is planned for tomorrow as well. After I return I can work on making my little application more interesting (embedded audio player, nicer presentation, maybe an embedded map, ability to come back later and attach related pictures…) and masssaged into a condition that wouldn’t be too embarassing to let others use. This “live neogeographical netcasting” thing is too much fun to keep just to myself. (I wonder how hard it would be to interface this with the Laconica microblogging system?…)

Further bulletins as events warrant…

“Antibiotic Susceptibility Testing by a Standardized Single-Disk Method”

Okay, one last post in the Classic Science Papers challenge before my time’s up:

Bauer AW, Kirby WM, Sherris JC, Turck M :”Antibiotic susceptibility testing by a standardized single disk method.” Am J Clin Pathol. 1966 Apr;45(4):493-6.

Petri dishes containing bacteria, showing inhibition of growth by certain substancesThe “Kirby-Bauer” antibiotic susceptibility test is another standard method that you should cover in microbiology class. The method involves getting a pure culture of the bacteria you want to treat, and then growing it in a petri dish. By putting paper disks soaked with various anti-bacterial substances, you can identify which ones are most effective at killing (or at least stopping) the bacteria in question – for example if you’re trying to figure out what kind of antibiotic to give to the guy coughing up some unknown plague in your doctor’s office… The anti-bacterial substance that the paper is soaked in slowly diffuses into the area around it on the petri dish, getting more dilute the further it gets from the paper. You can then estimate how powerfully anti-bacterial the stuff is by how far from the paper the bacteria stop growing.

The authors here didn’t invent this trick. Not all antibiotic-susceptibility tests are “Kirby-Bauer” tests (the blurry picture there is of an experiment I did involving the beer ingredient hops, and is not a Kirby-Bauer test. Click the picture to go to my “Beer Cures Anthrax” post from long ago…). What this paper describes is a method that finally standardized this test. Instead of having to use multiple paper disks with different amounts of the same substance, the “Kirby-Bauer” test prescribes specific concentrations of each antibiotic, and specific nutrient agar formulations, and so forth, so that determining which antibiotic your mystery bug is best treated with can be done in a way that gives consistent results regardless of who is performing the test.

The method is regularly updated to account for new antibiotics, but is still referred to as the “Kirby-Bauer” antibiotic susceptibility test to this day. Incidentally, the American Society for Microbiology kindly hosts a reprint of this paper as a .pdf file, so you can read it yourself if you’d like.

(UPDATE 20110328: new URL for the reprint of the paper. Thanks, Alex S!)

I’m not a real hillbilly, but I play one on the internet…

My first “Will It Ferment” project is now in process.

See, I’m stuck with a somewhat unpredictable schedule and a need to travel frequently, cramped spaces to work in at the moment, and a streak of gustatory perversion that I just can’t help an urge to rebel against purists at the moment.

Quick bit of background on that latter statement: I’ve noticed that people seem to think there are only two-and-a-half kinds of “real” non-commercial fermented beverages. There’s beer (which is apparently defined as a strong tisane of hops, flavored by mixing it into fermented malt), there’s wine (which is always made of grapes of course), and out on the fringes of respectability is Mead (“Honey wine”) which seems to be slowly gaining some acceptance as a mildly exotic brew. The attitude is that anything else you might want to brew (say, a beer flavored and preserved with something besides hops, or a wine made out of anything but grapes) is probably some quaint “country” (i.e. hillbilly) thing for people who either live too far from civilization or are too poor to just buy a “real” beverage, or are too ignorant to know the difference. Either that, or it’s just some desperate attempt to make something to get drunk on. Might as well be making pruno.

The attitude kind of annoys me, so I’m trying to make a sort of “free person’s pruno”. I figure if the end result is as palatable as it could be, it’ll probably resemble “Zima”. Uh, no, I don’t expect it to be great – this is merely an experiment. My must has an Original Specific Gravity (“O.G.”) of approximately 1.054, about the same as most lagers start out. As I write this, my gallon of must is on the stove in a stainless steel pot. I’m going to try to heat it to boiling and let it boil for a few minutes in hopes of driving off much of the benzoic acid in it, so as not to inhibit the yeast fermentation.

To your right, you should see the ingredients used in this project. Yes, those two bottles in the background are there on purpose. I’m trying to make…Mountain Dew Wine.

Here’s the plan:

  • Last night, I took a couple of clean glass 1 Qt milk bottles, rinsed them with iodophor solution to sanitize, let them dry. Then, I put about 12 ounces of tap water (unchlorinated) into one and dumped the contents of both yeast packets you see in the picture into it to rehydrate.
  • The yeast packets were opened over a year ago – I don’t even recall what I did with the tiny amount of yeast I poured out. They’ve been sitting in the ‘fridge since then. What’s more, they had expired in December of 2006 to begin with.
  • The two yeasts (Red Star Montrachet and Red Star Flor Sherry) were both mixed into the same container in hopes that I could encourage a yeast orgy, giving me as much genetic diversity as possible from the two strains and maximizing the chance that I’d be able to get a culture which can grow in flat Mountain Dew and whatever benzoic acid (from Sodium Benzoate) might remain in it. I had read that V8 juice was actually an excellent medium for inducing yeast sporulation. Since sporulation occurs as a result of yeast cells mating, I made a huge leap of logic towards thinking the V8 might maximize my chances of getting some yeast mating going on.
  • After a few minutes to rehydrate, I dumped the 12-ounce can of V8 into the bottle and shook well. I also crushed up a children’s chewable vitamin (see bottle at lower-left) and a small portion (perhaps 1/5) of a capsule of the L-Arginine as a nitrogen source and added them as well. I then poured it back and forth between the two bottles a few times to aerate, then split the mixture between the two bottles, capped loosely, and went to bed.
  • As of this morning, fermentation was obviously occurring in the mixture, so sitting in my fridge open for over a year hadn’t killed off ALL of the cells. I opened the bottles and swirled to re-aerate, and added about a tablespoon of “corn sugar” (glucose a.k.a. dextrose) to wake the yeast cells back up. Since then, I’ve been pouring a bit of Mountain Dew right out of a third bottle into each of the yeast starter bottles every couple of hours. The amount of bubbling I see suggests to me that fermentation is still going on (and is not just from the carbonation of the Mountain Dew). Hopefully this will help the yeast culture acclimate a bit to the benzoic acid.
  • I dumped the other 2 2L bottles of Mountain Dew into a stainless steel 8-qt pot and heated to boiling, whisking with a steel whisk frequently to help get the dissolved gases to bubble out (hopefully along with some benzoic acid in the steam). At this moment, it’s up to 75C (about 165F) according to the thermometer I have stuck in it. It’s steaming a bit, and I can smell some of the citrusy aroma boiling off, unfortunately. I was afraid that’d happen. UPDATE: our ancient stove with one working burner seems to have trouble getting this much liquid above 200F without cranking it up all the way and risking the bottom getting too hot. Since there’s a substantial amount of hot water vapor coming off, I’m going to hope that’s carrying away some benzoic acid and just let it start cooling down. I’ll stir it vigorously and frequently with the whisk until the temperature drops to about 160F and then I’ll cover it for the night.
  • Meanwhile, before I go to bed, I’m going to recombine as much of the two yeast culture bottles as I can into one bottle, then rinse out the other. In that one, I’ll mix up about 12 ounces of tap water and enough corn sugar to reach a gravity of about 1.050-1.055. I’ll crush up another chewable vitamin and about half of the remaining arginine capsule into it, mix well, and warm it with a quick spin in the microwave (no exact measurements, just until it’s “obviously warm” to the touch after mixing). Then I’ll shake the V8 culture well to mix, and splash about a tablespoon’s worth into the new bottle.
  • In the morning, I’ll re-aerate the new culture and add a tablespoon of corn sugar to wake it back up, then once it’s going, I’ll start adding the now-cooled cooked flat Mountain Dew to it in small increments. Assuming it keeps going, I’ll dump in the remainder of the L-Arginine capsule, crush in one last chewable vitamin, and them combine the new culture with the rest of the cooked flat Mountain Dew in a nice plastic 2-gallon “water” container that I picked up (already rinsed with iodophor and dried). Cap it with a latex glove attached with a rubber band as described in the “Pruno” entry in Leon Kania’s “Alaskan Bootlegger’s Bible” (Click image for link) just because I thought it was the funniest airlock design I’d ever run into. Yes, I am easily amused.
  • If I’m lucky, there’ll be so much live and active yeast in the second culture at that point that the fermentation will finish quickly, because I’m driving to Texas the following day. Alternatively, I may be lucky and the remaining benzoic acid will slow the yeast down, so I can safely leave it fermenting (sitting in my sink in case of overflow while I’m gone) for the week that I’ll be gone.

If I’m UNlucky, either it won’t ferment at all (and I can then use it to try to develop a Mountain Dew Tolerant strain of yeast), or it’ll ferment but taste utterly disgusting (in which case I can use it to try to obtain some Gluconobacter strains and make Mountain Dew Vinegar), or it’ll be “infected” and will already BE Mountain Dew Vinegar, which would also be pretty funny anyway. So, other than completely unforseen results, this experiment can’t be a TOTAL waste.

[Update 20080727: Preliminary results of this perverse project may be read In this more recent post…]

I finally got to Bristol Brewing Company…

Signage in front of the Bristol Brewing CompanyAfter spotting the company’s mention in Jeff Sparrow’s “Wildbrews“, I’ve been wanting to visit Bristol Brewing Company, particularly since they may be the only such brewery using local yeasts and bacteria that they isolated themselves from their local environment.

Since we’re moving from Southeastern Idaho to Southeastern Texas, I’ve been going back and forth between the two location. It just so happens that along with New Belgium Brewing Company, Bristol Brewing is actually right along a convenient route between the two locations. (Let’s see if I can figure out how to work the Google Maps plugin):

How’s that look? How does it work? (Those of you reading this on the RSS feed: The interactive map only appears on the website, it would seem. Please check it out here.) I made the KML file myself…

Bristol Brewing is a cozy little brewpub, and the people there are encouragingly helpful. They were in the middle of bottling, so there were no tours. Also, there were not currently any of the skull-‘n-bones beers available. However, I did get an educational series of tastes of their current brews on tap (thank you to the employee I spent most of the time talking to whose name I’ve embarrassingly forgotten, but who I believe was Tad Davis judging from the photos on the web site). I also lucked out and their microbiologist, Ken Andrews, happened to be there. I asked about their native Colorado brewing flora. Turns out Bristol Brewing isn’t quite as bold as I originally thought. They’re still doing their primary fermentation with “normal” brewing yeasts. What they’ve done is inoculated some wine barrels with the locally-isolated yeasts and bacteria, and they use the barrels for a secondary fermentation and aging instead. Much safer if you have to worry about having a drinkable product at the end, and of course it makes me feel like more of a crazed rebel for wanting to isolate my own local bugs for the main fermentation. So, a great visit overall.

Incidentally, it seems they’ll be tapping a new Skull-‘n-Bones brew in a couple of weeks, at 5pm on Tuesday, May 27th (2008). It sounds like they’ll probably have some available for a few days before it all disappears, so I’m hoping my return to Texas can be timed such that I can swing by and at least get a taste.

WANT: “Teamaker” hops

Just a brief “aw, crap, has it really been over two weeks since my last post?” post, really, but I thought this was interesting.

It would seem that there’s a variety of hops that’s been registered recently known as the “Teamaker” variety. It’s got all the magic bacteria-stopping power of a hops plant, but composed of almost entirely the non-bitter component. I’m not sure how hard it would be for me to get them to send me a plant or two to evaluate it’s usefulness for yeast cultivation (as an anti-firmicutes antibiotic) and for controlling the growth of bacteria in fermented foods and drinks…

House-hunting (“Yep, these are house droppings all right. Fresh ones too…” [everybody’s seen that Monty Python bit, right?]) in southeast Texas and the related travel (both in the area here and between here and the other abode in southeastern Idaho) is eating my life at the moment, but I’ll try not to neglect the blog so much.

More to follow.

The care and feeding of Saccharomyces

Let me pause now for a moment to review what I’ve learned so far:

  • Yeast are filthy little jerks
  • No, seriously. I’ve previously reviewed their promiscuous sex lives,
    their sexually-transmitted diseases, and their toiletry habits. Somehow, though I still want to do more brewing, so let’s continue.

    Bag of 'Parodina Yeast Chow'.  I am not affiliated with Purina Mills corporation!  This image is PARODY!

  • Yeast need to be fed particular sugars
  • The three major elements needed by pretty much every living thing for “food” are Carbon, Nitrogen (as reduced “amino” nitrogen), and phosphorus (as oxidized phosphate) (Reduced sulfur is also needed in small amounts for proteins). Glucose (“dextrose” or “corn sugar”), fructose, or sucrose (“table sugar”, each molecule of which is made of a molecule of glucose attached to a molecule of fructose) are all used as carbon sources by Saccharomyces yeasts. Possibly also Galactose under certain conditions[1]. Saccharomyces yeasts don’t appear to be able to use lactose (“milk sugar”, each molecule of which is made of a molecule of glucose and a molecule of galactose), so some recipes include lactose in order to ensure there is some residual “sugar” in the mix at the end, for flavor and “body”.

  • Yeast need reduced nitrogen (amino nitrogen or ammonia…or urea)
  • Aside from sugars, this seems to be possibly the most important yeast nutrient. The most
    “natural” source of this nutrient would seem to be amino acids or very short peptides (2-5 amino acids long). Apparently urea (carbamide) also makes a good yeast nutrient, but:

  • You don’t want TOO much nitrogen available to the yeast, or there’ll be excess urea dumped back into the brew
  • This could combine with the ethanol to make “ethyl carbamate”, which is considered
    a probable carcinogen, at least if it’s present at a high enough level. Obviously if you use urea as a
    yeast nutrient, that’s only going to increase the possibility of a problem.

  • Saccharomyces yeasts are effectively incapable of using proteins for nutrition.
  • Proteins can be a source of amino nitrogen (and carbon and sulfur), but like all real microbes, yeast cells cannot just “eat” chunks of protein. They have to be broken down into very small chains of amino acids or even as individual amino acid molecules before the yeast can suck them up and use them. Saccharomyces yeasts do not appear to normally excrete protein-digesting enzymes, so by themselves they cannot make any use of protein for nutrition[3].

  • Yeast need oxygen
  • Oxygen is necessary for making certain components of the cell membrane, in addition to it’s more obvious role in respiration. Without a way to replace used up membrane components, the yeast stop reproducing and eventually fall apart and die. There seems to be some suggestion that to a certain extent one can substitute some raw membrane material for oxygen here (either as “yeast hulls” or possibly even certain of the natural waxes on some fruits).

  • If you give yeast oxygen, though, they consume the sugars entirely instead of making alcohol…
  • …or do they? Between the “Crabtree effect” (when there are high concentrations of glucose, alcohol production continues even in the presence of oxygen) and indications in scientific papers[2], it seems SMALL amounts of oxygen may not be a problem, and might very well be beneficial.

  • Yeast need vitamins and minerals
  • B1 (“Thiamine”) is commonly mentioned, though apparently the need for it varies from strain to strain. Also potentially important are Pantothenic Acid (B5), Niacin (Nicotinic Acid, Vitamin B3), Biotin, Inositol, as well as Potassium, Magnesium, and trace amounts of calcium and a few other minerals[4].

  • Unhealthy yeasts are more prone to make (EEK!) Off-Flavors and Off-Odors (EEK again!)
  • For one thing, it seems to be a general rule that you don’t want your brew sitting on the corpses of dead yeast (the “lees” of wine, or “trub” of beer), because that is a potential source of (insert dramatic music and crash of thunder here)Off-Flavors and Off-Odors. Yeast dying and falling apart is also a major source of urea being dumped into the brew, too. Some strains of yeast under certain conditions, such as insufficient pantothenic acid, may be prone to producing nasty-smelling sulfides as well.

So, in most cases what we want to do when brewing is keep our yeast as alive and happy as possible, and get them to hurry up and finish our primary fermentation before they start dying off. Coming up: My (as yet untested) plot for accomplishing this – without specialized scientific equipment or materials.

[1] Wilkinson JF: “The pathway of adaptive fermentation of galactose by yeast” Biochem J. 1949; 44(4): 460467
[2] Nagodawithana TW, Castellano C, Steinkraus KH: “Effect of dissolved oxygen, temperature, initial cell count, and sugar concentration on the viability of Saccharomyces cerevisiae in rapid fermentations.” Appl Microbiol. 1974 Sep;28(3):383-91.
[3] Bilinski CA, Russell I, Stewart GG: “Applicability of Yeast Extracellular Proteinases in Brewing: Physiological and Biochemical Aspects.” Appl Environ Microbiol. 1987 Mar;53(3):495-499.
[4] Fugelsang KG, Edwards CG: “Wine Microbiology: Practical Applications and Procedures” 2007; Springer Science+Business Media LLC, New York; pg 17

More on the shocking life of yeasts

(Brief Update: Hello Ontario! Did I attract the attention of a Toronto homebrewing club or something? Anyway – welcome!)

I am amazed at how much depravity I uncover as I explore the mystery that is
Saccharomyces cerevisiae.

I’ve previously discussed how the filthy little beasts have drunken orgies and exchange sexually transmitted diseases with each other. Now I find out the inebriated little jerks are peeing in my beer, possibly to try to give me cancer!

No, seriously. Given enough “Free Amino Nitrogen”, for example in the form of the pirate’s favorite amino acid, like tiny little single-celled bladders, the yeast will start excreting extra nitrogen in the form of Urea all over whatever they’re growing in.

Of course, the whole time they’ve also been excreting ethanol. It turns out, under certain conditions urea (more formally known as “carbamide” nowadays) and ethanol will combine like drunken evil “Wonder Twins” to form Ethyl Carbamate.

Front Cover of the bookI ran into this as I was reading through my shiny new Wine Microbiology book, which has two pages on this yeast pee byproduct. An article linked to from fark.com recently reminded me of it and prompted this post.

To be honest, this seems a lot like the acrylamide media circus (compare the two links…) that popped up back in 2002. In both of these cases, we’re talking about a substance that occurs as a natural result of the preparation process rather than some new industrial chemical, and in both cases the processes in question have been around probably since prehistory. And in both cases, the real situation seems to boil down to something like “pay attention to your preparation technique, and if you try to live entirely on a diet of overcooked French fries and dessert wines, you might be at an increased risk for cancer.” QED. Or perhaps DUH.

Other than not trying to live on a French McDonald’s diet, there are some things you can do when you brew to limit ethyl carbamate formation. Put very simply: don’t overfertilize your grapes because that can directly lead to unnecessarily high levels of nitrogen available in your wine, and don’t leave your bottles of brew in hot conditions for long, because ethyl carbamate forms faster in hot conditions.

There, problem solved. A more detailed “ethyl carbamate preventative action manual” may be found here. Meanwhile, I’m pretty sure our favorite drunken little micro-hedonists are too busy partying and making our wines and beers to be plotting our cancerous dooms.