Thursday, April 18, 2013

Local Lambic - Part 1: The "Bugs"

After reading a blog post by The Mad Fermentationist that Scott (SNB Brewing) sent to me 2 years ago, I decided to brew a beer and ferment it using a local wild starter, thus my Local Lambic project was born.

In order to capture my local wild yeast & bacteria I boiled up some wheat DME with Styrian Golding whole hops - O.G. 1.027 with an IBU of 23. The half gallon of cooled wort was divided into 3 shallow vessels and covered with cheese cloth. A sturdy rubber band was affixed to hold the cheesecloth in place and keep any big bugs and leaves out while the starters were set out overnight to be inoculated.

One was put in the washing machine near my brewing are in our garage.
Both side doors were left open so it would be exposed to a draft breeze all night long.

One was put in the middle of our vegetable garden.

One was put on the other side of our back yard near several citrus trees.

My plan was to allow each starter to ferment individually to see what developed from each inoculation location. Any rank foul starters would be dumped. If any of the little starters goes bad I'll be able to smell and taste it. Only the good ones make it to the next round where I would increase the cell count with a larger starter Hopefully, I'd work up enough yeast and bacteria to ferment a 5-gallon batch of homebrew.

With this approach I wasn’t forced to just roll the dice and hope spontaneous fermentation happened with the right mix of yeast and bacteria after investing the time and money to brew a full batch with the hope that it would ferment into something flavourful.

The wort “Petri” dishes made it through the night OK, but one earwig made its way into the wort left in the garden. Who knows what type of “bugs” were on that bug! In the future, I recommend using a double layer of cheese cloth to keep out the med. size bugs too.

Here's the collection of 3 canning jars with inoculated starters that were nice and safe after a night of running wild in the back yard...

In just 2 days, one of the starters was already starting to show signs of fermentation! Go figure, the one that had the earwig fall into and it’s the one that got going first!

By the 3rd day, all 3 of the inoculated “Lambic sisters” were fermenting away nicely. They all still smelled like fresh wort at that point. No other distinct aromas, but more importantly, there were no noticeable off-aromas!!

At that point it was full steam ahead for the project - Ramming Speed!!

What was collected from my back yard was definitely some type yeast, but the wort could also contain bacteria like lacto., pedio., etc., and probably some brett. I kept my fingers crossed that the earwig didn’t add any e.coli from the planter soil or any other nasty bugs. Luckily, “bad bugs” make beer smell and taste bad and the low pH of fermenting wort kills off e. coli. The blog posting from The Mad Fermentationist that Scott mentioned to me talks about this stuff in detail and is a real eye opener on how to logically and safely collect ambient yeast and bacteria for use with homebrew.

I also created sour starter that used raw grain to create some soured wort that went into the wort once it cooled below 110 degrees. This was done to create add some complexity to the sourness in the beer and help drive the post-boil pH down. It also ensured I had desirable bacteria in the mix.

My plan was to conduct primary fermentation in glass and then age in stainless steel. Both can be easily sanitized afterwards. I couldn't match the oxygen that permeates through oak, but I planned on opening up the corny keg and allow fresh oxygen in to help control the brett., pedio., lacto. & acetobacter. Other than that it's a bit of a crap shoot - as they say "Relax, have a homebrew”

I tried to control what I could, and prayed the rest went down the right road. I’d never done this before, so it’s as much a learning experience as a chance to manage a fermentation that is much more complex than any other I've attempted.

After 3 weeks, all 3 starters had a yeast cake at the bottom, and 2 out of 3 have signs of brett. too. I think the secondary oxygenating I did increased the amount of brett present - nice white film on top of the starter.

Because all 3 starters came out so well, I combined them to inoculate a full gallon and a half starter for the Local Lambic. I oxygenate the new starter by shaking it quite a bit in order to grow the max. amount of yeast cells. They'll have to do the bulk of the fermenting of the wort after all. The rest of the bugs in the mix would do their thing afterwards with the “scraps” after primary fermentation was finished.

The yeast, etc. grew nicely in the second starters. Whenever I shook up the bottles, the amount of latent carbonation is amazing!

Houston, I think we are ready to start countdown for liftoff!

While the aroma of the starters was becoming less "worty" I had not tasted it yet. The real flavor of a Lambic doesn't come from the yeast anyway. It smelled fairly clean with a faint lemon aroma.

I'll planned on giving it a taste a week later to see where it was at, but I needed it to ferment for a while to make sure there's no chance of e. coli before tasting it. Luckily, the drop in pH caused by yeast fermentation kills off a lot of really bad bugs. The yeast cake at the bottom is a bit dark, but it's nearly 1/4" thick now!

I wanted to ensure I had all the hallmark bacteria found in lambic fermentation, so I supplemented the wild yeast & brett. I’d captured with bacteria from the grain used in the mash. I made the soured wort as outlined in a BYO article to add to the cooling wort. I boiled 42g. of wheat DME in a pint of water for 20 min. When it had cooled to 110 degrees, I added 1/3 cup of slightly crushed Belgian Pilsner malt. The whole mass came to 100 degrees. It would need to sit insulated with a heating pad under it to keep it between 100 and 120 for the next 3 days. Grain husks have bacteria on it that will attack and eat the sugars in the starter. I hoped yield a good bit of lactobacillus & pediococcus which I planned to pitch into the cool-ship once the wort was about 100 to 110 degrees Fahrenheit. As the wort cools slowly overnight, it will give the bacteria time to grow before the yeast is pitch.

Here are some photos of how I created the Sour Wort Starter

Close up of crushed malt

Starter and crushed grain.

Grain in the starter wort

Starter was snug as a bug. I pushed a food thermometer right through a small hole I make in the lid in order to constantly monitor the temperature accurately.

Starter resting nicely at 100 degrees

4 days since the soured starter was “brewed” and it has really taken off!

The Local Lambic starters didn't show signs of either of these bacteria, but they gave me signs of Yeast and brett. activity. The two starters together should make for a good lambic with some complexity to the sourness.

In Part 2 (due in Mid May) I’ll discuss the brew day, fermentation and final flavor profile of my Local Lambic. How to make your own cool-ship and lessons learned will be included too!

Wednesday, April 3, 2013

Oxygen Flow Meter for a disposable oxygen tank

Years ago Liquid Bread came out with what was probably the first oxygenation setup for homebrewers that included a tank of Oxygen (Bernzomatic), a regulator, hose and a 0.5 micron stone. I still have all of the reusable parts to that kit over a dozen years later.

While I’ve read how much oxygen ppm a brewer should try to achieve, it was impossible to calculate if my method was helping me achieve my goals. I’d open up the valve until I was at a flow rate where the bubbles were gently breaking the surface of the wort, but it was always a guess if that was the right way to do it.

While reading Yeast by Dr. Chris White and Jamil Zainasheff I came upon some solid info. on how to achieve various levels of oxygenation so long as I could ensure my flow rate was 1 liter per minute (lpm).

Unfortunately, the regulator from Liquid Bread is rudimentary and couldn't be modified to attach a quality flow meter. I did not want to use a cheap inline flow meter which would require me to grow an extra set of hands to keep it hanging vertically, so I decided to build my own setup from scratch.

The parts:
  • Pediatric Flow Meter
  • Regulator for a Disposable Oxygen Tank for jewelers
  • DISS 1240 to 1/8” npt Adaptor
  • 1/8 npt female to male Adaptor
  • Plastic Toilet Flange
  • Gas Line Teflon tape

The flow meter scale – 1 lpm was my target….easy to read on this scale! When the oxygen is flowing, the ball hovers and reading the flow rate is extremely simple. The middle of the ball is where I take my reading.

The old "dumb" regulator and the killer new one I built. 

This is the special DISS to npt adaptor from Bay Corp. with the butt end of the flow meter to the left and the standard barb attached on the right.

This is the 1/8” npt female to 1/8” npt male adaptor joining the flow meter to the regulator. The regulator out flow has a male reverse flare fitting.

Unfortunately, I could not locate a female reverse flare to 1/8” npt male adaptor, but the adaptor I used tested negative for leaks. Use the right adaptor instead if you can find one.

The entire setup with the new toilet flange base stabilizes the oxygen tank
and makes operation hassle free.

Where to get the parts and where to use in the build: 
  • From a seller on eBay I bought a Pediatric Flow Meter for $22.00. I highly recommend using a pediatric flow meters because the scale is from 0 to 3 lpm, so measuring my goal flow rate of 1 lpm is easy. The standard flow rate meters I saw for sale have a scale that does from 0 to 8 lpm, so the pediatric meter is much easier to read.
  • From a seller on Amazon I bought a Regulator for a Disposable Oxygen Tank normally used in the jewelry business for $33.00. It comes with a threaded connector, so I would be able to attach the flow meter.
  • Bay Corporation makes a DISS 1240 female to 1/8” npt female adaptor (P/N  1242-8). This is needed for the outflow side of the flow meter so I could then attach a 1/8” npt male to 1/8” barb connector. This special adaptor is hard to find. It’s only available from many medical supply companies. I bought mine for $8.92 from
  • I also bought a 1/8” npt female to 1/8” npt male adaptor to attach the flow meter to the tank regulator. The threads on the regulator are actually 1/8” male reverse flare type. This is nearly identical to npt. The tpi is the same, but the taper is different between the two types of pipe. The reverse flare has nearly no taper at all, so I had to use 2 wraps of gas line Teflon tape and screw the adapter all the way on and give it a good crank to ensure it was down to the narrowest part of the adaptor and was properly sealed. I successfully tested and passed the seal between the fittings using a soapy water test like you would use to find a leak in a bicycle inner tube. Please use the correct female reverse flare to male npt adaptor if one is available so you can be confident your oxygen isn’t leaking out during use.
  • In the end, this setup gives me two valves where I’d prefer to have one. Once the tank regulator is opened up, it’s easy to set the flow rate using the valve in the flow meter.
  • Having the flow meter stick out caused the tall, skinny oxygen tank to be unstable and it wanted to fall over pretty easily. Luckily, a Plastic Toilet Flange from Lowe’s has an ID of 3” which is a perfect fit for the disposable oxygen tank which is 2.9” diameter. Cost was just under $5.
  • I used Gas Line Teflon tape for all fittings. Oxygen is far too flammable to mess around with, so I played it safe.

Total cost for this custom made flow meter for disposable tanks was just over $70. That’s about triple what a “dumb” tank regulator from a homebrew shop costs ($19.99 at Williams Brewing), but without knowing the flow rate it’s is very hard to consistent when oxygenating your wort for those big beers that need more than 8 ppm. 

Friday, February 22, 2013

EisGersteWein – zweiter Teil

When we last looked in on twenty13 it was starting to freeze at about 22° F and just about ready to be extracted into a 3-gallon corny keg. I dropped the temperature of the beer a bit more, driving for the 18 degrees that my calculations told me would concentrate it enough to achieve 20% abv. It got down to 10° F, so I warmed it back up to between 15 & 16° F. This temp worked out just fine though because the keg-to-keg beer transfer was going to happen outside of the freezer chest. If anything I wanted the beer temp. on transfer day to err on the conservative side. If my yield was less than 2.75 gallons, I knew I could always “water down” the beer to reach 20% abv, but it would be a lot more work if I erred the other way around.

Freezing twenty13 to concentrate the alcohol, residual malt and hops was fairly easy, but it wasn't without a couple minor mishaps. After taking the picture of the keg contents that’s in my previous post, I forgot to repressurize the keg and when the temperature was dropped to 10° F, about 1 quart of slushy beer made its way past the lid o-ring and onto the floor of my freezer chest. It smelled great, but was a sticky mess to clean up.

I used my new Spunding Valve to regulate the transfer rate and to make it a closed transfer to avoid any chance of oxidation. It also kept the recipient keg slightly pressurized which helped minimize the foaming that inevitably happens at the end of transferring a beer in this manner. After transferring the contents from both originating kegs I ended up with only 2.25 gallons. I bounced both kegs a few times to get any trapped liquid moving to the bottom of the keg. Within 5 more minutes I was able to transfer an additional quart. About half an hour after, that I was able to get the final few ounces transferred so my final volume was approx. 2.7 gallons.

Once the transfer was finished, the ice in the keg was white and lacked any malt color. It took another day and a half for the contents of the kegs to completely thaw. There was some color and a little flavor to the fluid that I ended up pouring out. I felt really good about how much concentration I had achieved, but I had yet to test the EisGersteWein twenty13 to confirm I’d achieved my goal.

The original beer had an OG of 1.066 and a FG of 1.018 (5.8 Brix), so the original abv was 6.06%. The freezing would increase the alcohol(abv), residual malt (FG) and hops (IBU’s) about 330% so long as I concentrated the original 9 gallons down to 2.70 to 2.73 gallons. The only empirical measurement I could use in my brewery was measuring the FG after all was said and done. I used my refractometer and it read just over 19.0 My calculated goal was 19.1(5.8 x 3.3) to reach 20.21% abv. Short of using a laboratory to confirm the actual alcohol level, I’d say the goal abv was reached. To validate the beer as a success though, the beer had to pass a taste test too.

I belong to a small group of very committed homebrewers – Tao of Brewing. Most of us have been brewing for over a decade, some of us for nearly two decades, but there are some members who've been brewing for only a few years. Our group was formed to give and receive honest evaluation of our beers that don’t any hold any punches. Honest feedback is the goal so that we all make the best beer possible.  

At the meeting this past Wednesday I served the first samples of twenty13 and my fellow brewers said they tasted:
  • Huge London Pride/Fullers ESB malt flavor from yeast esters.
  • Bittering and flavor hops there but no hop aroma.
  • Balanced malt to hop bitterness.
  • Alcohol hidden but hits in aftertaste.
  • British, bready, biscuity.
  • Honey and chamomile.
  • Toffee & medium crystal flavor notes.
  • Irish whisky-like flavor notes as it warms.
  • Definitely beer-like.
  • Can smell alcohol slightly.
  • Dry hoppiness lingers in finish.
  • Strangely dry for a beer with such a high FG
  • Loooooong dry, hoppy finish.
  • Final verdict: intense, balanced and awesome!

Again and again, tasters were surprised at the alcohol level and they commented on how well balanced the beer tasted. Many of them lamented on how bad Sink the Bismarck tasted to them. They found that beer to be unbalanced and commented how overbearing the hops were in it. These guys are no shrinking violets when it comes to hops, but they don’t like BrewDog products in the least. In twenty13 I planned for the concentration of the hop bitterness and flavor, but I was truly surprised at how well that aspect of the finished beer came off.

In any case, I’m very proud of this beer and can’t wait to force carbonate & bottle it so I can share it with friends and family…now if I could just find 187 ml BROWN bottles somewhere!

Thursday, February 21, 2013

As promised, The Spunding Valve explored:

To Spund is the German term for To Bung, To Close Up or To Seal, not some trendy photo pose that’s the next best thing since Planking. A Spunding Valve is a device that has a Pressure Gauge to show vessel Pressure and a Release Valve to vent excess Pressure from that vessel.

    • Spunding, in the brewing sense, refers to the act of closing off a vessel containing beer or wort and allowing Pressure to build inside the liquid.                                - By WortMonger in

While WortMonger’s definition makes a Spunding Valve sound suspiciously like something involved a case of blue balls, not to worry, it’s actually a good thing.

  •  It can be a useful way to naturally carbonate a beer.
  •  It can also be used to help transfer carbonated beer from keg to keg without    losing any carbonation.
  •  In my case, I used one to vent the Pressure that would build up as I transferred the twenty13 EisGersteWein into a 3-gallon corny keg.

Spunding Valves can also be used to regulate the transfer of beer from one keg to another while under Pressure. While that is a great convenience for my EisGersteWein, it is downright necessary if transferring carbonated beer from one keg to another.

I didn’t want any chance of oxygen coming in contact with my EisGersteWein, so after purging the recipient keg of oxygen with CO2(@10 psi – twice), I wanted to keep its lid sealed. Instead of manually releasing the Pressure in the recipient keg as it built up during the transfer, I decided to make my own Spunding Valve. 

Here are the parts needed to build your own Spunding Valve.

 The Valve and Pressure Gauge were purchased on

WIKA 9767045 Industrial Pressure Gauge, Liquid/Refillable, 
Copper Alloy Wetted Parts…$15.00

Control Devices CR Series Brass Pressure Relief Valve,
 0-100 psi Adjustable Pressure Relief Valve…$9.95

The Pressure Gauge, Relief Valve and most of the brass fittings used ¼” npt thread. the other plumbing fittings (female flare swivel, male flare to male NPT adapter, and NPT tee) were bought at my local hardware store.

While some homebrew shops offer similar Spunding Valves, their Pressure Gauges only go up to 15 psi. I bought a slightly more expensive Pressure Gauge that had a stainless steel body, with a wider psi range and that was also liquid filled. These are sturdier and I plan to use it for future carbonation projects. You can probably buy a basic Pressure Gauge that will suffice for only $5.00 though. Total cost for my Spunding Valve was approx. $40.

To use a Spunding Valve in a keg-to-keg transfer, make sure the recipient kegs is pressurized at a slightly lower pressure than the originating keg so there’s no chance of having anything flow backwards through the transfer lines. Hook up your CO2 tank to the originating keg and purge the transfer line so it is full of beer. Finally, attach the transfer line to the recipient keg. The beer should start flowing immediately. 

Eventually, the pressure will be equalized between the two kegs, so slowly open the Relief Valve until you hear the hiss of CO2 gas escaping so you can regulate the rate of the beer flowing into the recipient keg. Once everything is equalized, the Pressure Gauge should read about 2 to 4 psi lower than the Pressure Gauge on the CO2 tank hooked up to the originating keg.

As the transfer comes to an end, be careful to cut off the flow between the kegs so only liquid gets transferred. Allowing CO2 through the transfer hose will cause foaming in the recipient keg, and oxidation of your beer will happen if any air makes its way through the line. If any beer, or beer foam, makes its way into the Pressure Gauge or Relief Valve, it will be nearly impossible to clean….not that it happened to me or anything.

The Relief Valve I used show it was set to about 25 psi when the Pressure Gauge clearly showed the pressure in the recipient keg was between 8.5 & 9 psi…lesson learned!  – Follow the reading on the Pressure Gauge instead of the reading on the Relief Valve. Heck, you may want to buy an unmarked Relief Valve instead.

As for using a Spunding Valve to capture enough CO2 to pressurize and carbonate a beer in a corny keg…that will have to wait for a future post.

Friday, January 25, 2013

Twenty13 – EisGersteWein (Ice Barley Wine) – Part 1

          Last year I finally brewed a beer that broke the 1.100 mark. When it finished fermenting, it was my highest alcohol beer yet clocking in at 11.24% ABV. Then I heard all the buzz about Armageddon from BrewMeister (joke of a name!!) which clocks in at a whopping 65% abv. Damn buzz killers!  Envy set in quickly. For those who don’t already know, Armageddon is “freeze distilled” which removes water from the beer in the form of ice and leaves the residual malt sugars, hops and alcohol concentrated. It got me thinking about the time I was cold conditioning a bitter and accidentally froze it. The one gallon I got from the carboy was around 22% abv. !!

          I thought it would be great to do it right this time aiming to break the 20% abv mark. Most commercial breweries try to extrace 5 to 10% of the water as Ice, but BrewMeister must be extracting about 75%+ to achieve their 65% abv in Armageddon , so I decided to aim pretty high and try to match them with 68% of the water being extracted. It's not as hard as what they do to achieve a 130 proof beer, but it would be a good achievement if I could do it. I started with my Fullers London Pride clone recipe, then I increased all the malts by 60% and cut the hops by one third so the concentrated beer wouldn't be too bitter. Once the beer is frozen and concentrated, I hope the hop profile will measure around 75 IBU so the beer would still be balanced and drinkable.

          On brew day it was only 46 degrees outside. That’s pretty chilly for Orange County, CA.  I mashed at 151, but the day was so cold it dropped to 144 in no time even though the mash tun had a sleeping bag wrapped around it for insulation. Once I got it back up to 151 the conversion completed right away. In the boil I used First Wort Hopping to try and lock in a good amount of hop flavor too. I ended up with 9 gallons with an O.G of 1.065, but the effective OG is around 1.210 because of my plan to freeze the finished beer.
The English Ale (WLP002) yeast did an average job of fermenting the beer down to around 1.016 even though I wanted it to end up at 1.010. WLP002 is a VERY floccuative strain, and the cold-snap we had put it to sleep before I could really push the yeast.

(The twins)

          It looks like I’ll get about 2.75 gallons of beer at 20% abv, 75 IBU with an effective FG of 1.052. This should be a very rich winter warmer if I’ve ever heard of one! Most strong Barley Wines have a little less than half the alcohol and half the FG, but my IBU’s are right in line with the most American Barley Wines.

          Last night I used my Marks Keg Washer for the first time to clean up two kegs. After siphoning the beer into both, I ended up leaving 2 to 3 quarts of headspace. I’ll need this because the water in the beer will expand as it freezes. I hope to get the same chunky ice crystals I had in my accidentally frozen bitter. 

          My chest freezer was set to 20 degrees the day before the kegs were put inside. The kegs were put in the corner to maximize the cooling effect.

          After one day the beer was already a slushy at 23 degrees. According to laws of chemistry I will need to drop the beer to 18 degrees F in order to concentrate the beer to 20% abv. I turned the freezer down 10 degrees and gave each keg a swirl to get more ice to float up and liquid to separate downward.
(Beer Slushy anyone?!?!)

Geek Alert!

In order to figure out how much alcohol you want left in a liquid state you need to calculate how low of a temp the beer needs to reach.

Formula to calculate temp C needed for target ABV is:

=(((Target ABV/1.25)*1000)/46.06844)/(1-(Target ABV/1.25))*1.86*( -1)
Convert the Target ABV% to its decimal equivalent for the above formula.

Some results from this formula tell us how far down we need to drive the temp on our finished beer so the extracted EisBier has the alcohol level we desire.

10% abv   - 3.5 C  or    25.68 F
20% abv    -7.7 C  or    18.16 F
30% abv  -12.7 C  or      9.15 F
40% abv  -18.9 C  or    -2.20 F
50% abv  -26.9 C  or  -48.45 F

Please note that a tiny bit of the alcohol and the hops will be caught up in the frozen water, but the vast majority will make it into the beer you extract.

In the next installment we’ll discuss Spunding Valves….they’re not as kinky as they sound, but they can be very useful when you need to relieve some pressure or used to naturally carbonate when your beer is sitting in secondary in a corny keg.

Monday, January 21, 2013

The new home of The Homebrew Dude

Many years ago I answered brewing questions from around the world on a friend's web site called  I thought it would be fun to start a blog where I could help out fellow brewers again and share the discoveries I've made during my own brewing sessions, so Brewnundrum was started.

In this blog I hope to explain in the scientific cause and empirically observable effect of what we do as brewers. George Fix did that really well in his second book An Analysis of Brewing Techniques. Every brewer needs "skills" in their arsenal so they can brew world class beers. I hope this blog helps explain brewing situations and how to handle them if you don't have an arsenal of scientific instruments at your disposal. I encourage everyone to develop their brewing "skills", know how to use them, recognize when they're needed and understand how they all work together so you can brew world class beers. Simple, right?

A little about me: I'm just a homebrewer, but I'm in my 20th year of brewing now. While not an active judge, I attained National Judge ranking with the BJCP. I've attended the Advanced Homebrewers course at the American Brewers Guild, the Introduction to Brewing course at the UCSD Extension, and the Introduction to Brewing Science at the UCR Extension. I've run beginning and intermediate homebrewers' classes, made many presentations at homebrew club meetings, done several all-grain brewing demonstrations for local homebrew supply stores. I am also a past president of the Crown of the Valley Brewing Society. 

Several of my beers have won, or placed 2nd at the AHA National Homebrew Contest (regional round) and at the America's Finest City brewing Contest. While I brew all styles of beer and hard cider too, my current focus is on brewing beautiful, varied Saisons, Trappist style ales and the Soured 7 barrel project which Scott Bennett has mentioned in his blog previously. 

Needless to say, my homebrewing friends think I'm a bit of a brewing geek. My style of brewing is very grounded in the creative craft side of home brewing, but it is also well grounded in scientific and mathematical brewing principals....I brew by the numbers as I say because they tell me a story.

Saturday, January 19, 2013

Original Aeration Presentation


From Wikipedia: Aeration (also called aerification) is the process by which air is circulated through, mixed with or dissolved in a liquid or substance.

Aeration of liquids (usually water) is achieved by:

  • Passing the liquid through air by means of fountains, cascades, paddle-wheels or cones.
  • Passing air through the liquid by means of the Venturi tube, aeration turbines or compressed air which can be combined with diffuser(s) air stone(s), as well as fine bubble diffusers, coarse bubble diffusers or linear aeration tubing. Ceramics are suitable for this purpose, often involving dispersion of fine air or gas bubbles through the porous ceramic into a liquid. The smaller the bubbles, the more gas is exposed to the liquid increasing the gas transfer efficiency. Diffusers or spargers can also be designed into the system to cause turbulence or mixing if desired.

For Homebrewers: Adding dissolved oxygen to cooled wort for the benefit of the yeast.

Why aerate your wort?

Healthy happy (California) yeast make good tasting beer.

o    Too little dissolved oxygen results in
        • Low and sticky fermentation
        • Off flavors
        • Poor yeast crop
        • High ester production, resulting in a fruity-tasting beer
        • Low alcohol production
        • Better opportunity for unwanted wild yeast and bacteria to dominate wort

o    Too much oxygen causes

§  Rapid fermentations, resulting in excessive yeast growth and beer losses

§  Low ester

Yeast need to synthesize sterols (fatty acids) that are not normally available to them in the wort. When they have done this, their outer membranes are permeable thus allowing the sugars in the wort to be digested so alcohol and carbon dioxide can be created. Note: Olive Oil contains the very same fatty acid the yeast are trying to synthesize. Yeast can also use some trub to help in the synthesis of the needed sterols.

Fermentation and propagation\reproduction take energy. The yeast must build up their energy stores and grow\bud until they reach the proper density to start switching from aerobic to anaerobic metabolic pathway usage. Alcohol is a byproduct of anaerobic metabolic activity. Aeration helps yeast build up their initial energy stores to accomplish both of these main tasks.

When is the best time to aerate your wort.
  • After the boil, once the wort has been cooled to pitching temp.
  • Aerating the wort as it enters the chiller increases cold break and darkens the beer.
  • Aerating wort with yeast already pitched into it can be beneficial depending on method of aeration
  • After the wort has been fully cooled for lager fermentation and the settled trub has been removed or minimized.
When is the wrong time to aerate your wort?
  • Aerating hot wort can set off staling reactions – some controversy on this theory
  • After fermentation has already started as this can stall fermentation as the yeast switches back to aerobic metabolic pathways again. Need to be careful if racking to secondary.
  • Aerating fermented wort can cause alcohol molecules to cause stale tasting aldehyde molecules.

 Aeration methods

  • Splashing wort – easy and no cost
  • Use of Venturi device – easy and minimal cost
  • Oxygen stone with air pump in conjunction with a sterile filter – much quicker infusion of DO for a moderate cost.
  • Oxygen stone with tank of pure oxygen - Very quick infusion of DO with slightly higher cost.
  • Household Hydrogen Peroxide – very cheap but cannot be use in wort with pitched yeast Not Recommended! -  See Aeration Revisited

From Wikipedia:

On a given volume of air or liquid, the surface area changes proportionally with drop or bubble size, the very surface area where exchange can occur. Utilizing extremely small bubbles or drops increases the rate of gas transfer(aeration) due to the higher contact surface area. The pores which these bubbles pass through are generally micrometre-size.

Other things to consider
  • One drop of Olive oil will give yeast all the fatty acids needed to develop permeable membranes, but does not help speed the development of energy stores.
  • Aeration can be done multiple times in the first few hours after pitching yeast.
  • Nearly impossible to surpass 8ppm DO unless pure oxygen is used
  • Air is make up of only 21% Oxygen

How much to aerate the wort

·         Target is 8ppm to 12ppm of Dissolved Oxygen (DO). Varies by yeast strain and desired amount of esters contributed to the finished beer. To achieve 8ppm it takes:
    • About 30 minutes of shaking a fermenter manually
    • 15 minutes with air pump and aeration stone
    • 20 seconds with tank of pure oxygen and aeration stone - 15 ppm in 80 seconds
    • 2/3 to 1 ml of hydrogen peroxide per gallon of wort about 20 minutes before pitching yeast. Not Recommended! -  See Aeration Revisited
    • You’ll get about 4ppm just by allowing cooled wort to drain into fermenter using a siphon spray attachment on the end of the hose.

My Recommendations;
  • Clean\non-fruity  Ales (Most English and American ales) High DO (10 to 12),
    • Med. Pitch Rate (1/2 gal. starter / 5 to 6 gallons wort) & Med to Low Fermentation Temp 70 to 64 degrees 
  • Fruity Ales: Med DO, Med Pitch Rate (1/2 gallon starter pre 5 to 6 gallons of wort) &
    • Med to High Fermentation Temp. (72 to 85 degrees
  • Lagers: High DO (12+), High Pitch Rate (1 gallon starter per 5 to 6 gallons wort) &
    • Very Low Fermentation Temp 40 to 50 degrees
  • High Gravity beers; increase DO, increase pitching rate, use highly attenuative yeast strain, and allow fermentation temp to rise as fermentation finished, rouse yeast by swirling wort in fermenter as fermentation slows.
  • Too much DO can actually kill all character from the yeast. Example – WL English Ale yeast with 5ml HO3 in 6 gallons and fermented at 66 degrees is nearly flavorless. Using 3.5 to 4 ml in the same size batch and fermented at 67 to 68 degrees is a nearly perfect balance while fermented at 74 the esters will dominate.

Pitch enough yeast, feed them and aerate them well and keep them in a cool dark place and they’ll reward you with a flavorful beer that has a balance of character from the raw ingredients and your hand in steering the yeast to add just enough of their own special flavors

 Once you master these basic rules you can start bending the rules to make truly unique beers!

Information Sources

  • Books;
    • Principles of Brewing Science (1st ed.) by George Fix
    • An Analysis of Brewing Techniques by George & Laurie Fix
    • How to Brew (1st ed.) by John Palmer
    • Yeast by Chris White and Jamil Zainasheff

 Aeration and beer flavor

                Aeration is part of a pyramid that determines the majority of your beers flavor along with Pitching Rate and Fermentation Temp. These three components determine how your yeast will attenuate the wort and what flavor compounds they will contribute to your beer.

How temperature affects rate of oxygen going into solution from aeration

*You can see that it is nearly impossible to oxygenate very hot wort but the cooler your wort, the more susceptible it is to oxygenation.

How to calculate starter size to get the right pitch rate

750,000 x Volume in liters x Original Gravity in Plato

5.25  gallon of wort in your fermenter is about 20 liters.
If your O.G. is 1.061 that would be about 15 degrees Plato. 

750,000 x 20 x 15 = 225,000,000 yeast cells