Calculating ABV for Sour Beers

Yesterday I got into a discussion about what adjustments needed to be made to accurately determine the alcohol content of a sour beer. I’d always assumed that the souring process didn’t have much effect on the standard method, using a formula that takes into account the OG of the wort and the FG of the beer, but I’d never spent any time looking into it.

When we calculate the amount of alcohol in a beer we are judging the relative density of the wort before- and after fermentation. This reduction in density (specific gravity) comes from a couple sources (including yeast biomass growth), but most of it is from the conversion of sugars in the wort to ethanol and carbon dioxide by fermentation. I’d always read that the CO2 escaping into the atmosphere was the main cause of the reduction in density during fermentation.

During a clean fermentation a single molecule of glucose is fermented to create two molecules of CO2 and two molecules of ethanol. So our formula is only valid if one molecule of CO2 produced always means the creation of one molecule of ethanol. Luckily alcoholic fermentation is the same regardless of which brewing yeast (Saccharomyces or Brettanomyces) is responsible. However, these aren’t the only microbes at work in a sour beer.

The production of lactic acid by homofermentative strains of lactic acid bacteria utilizes sugar to make lactic acid and essentially nothing else (no CO2 is produced). This could theoretically lead to a higher FG than otherwise as these sugars would not be available for alcoholic fermentation, but it wouldn’t disrupt the calculation of ABV because these microbes don’t generate carbon dioxide as a byproduct. So our original assumption is still valid.

The heterofermentative production of lactic acid produces 1 molecule of lactic acid, plus 1 molecule each of CO2 and ethanol from each molecule of glucose. As a result you’ll still get the same gravity drop for each unit of alcohol produced. The molecule of lactic acid is incidental, similar to homofermentative lactic acid production.

This spurred a question about what was really causing the gravity of the wort to drop as it is fermented: the loss of CO2, or the addition of ethanol? To get a lower density we either need to decrease the mass, or increase the volume (because density is mass/volume). As I’ve never finished with more beer than the amount of wort I started with, I assumed that the loss of weight to gaseous CO2 made sense.

It turns out that fermentation converts sugar into 51.1% ethanol and 48.9% CO2 by weight (a mol of ethanol weighs 46.07 g, a mol of CO2 weighs 44.01 g). A 20 L batch with an OG of 1.050 weighs 21 kg (water weighs 1 kg/L, this wort is by definition 5% denser than water). If fermentation generated 5% alcohol by volume, this would be 1 L of ethanol (which has a density of .789 kg/L). So .789 kg of ethanol. This means that we've fermented 1.544 kg of sugar, and created .755 kg of CO2 in the process. If the total volume remained constant, we'd have 20 L of beer with a weight of 21-.755 = 20.245 kg, divided by the weight of 20 L of water (20 kg) gives us a gravity of 1.0123.

Plugging those numbers (OG=1.050, FG=1.0123) into an alcohol calculator I get 4.95% ABV. Which is almost exactly what we'd expect given that 5% ABV was one of the conditions I specified. This indicates that most the gravity lost is in fact a result of CO2 leaving the beer.

However, it brings up an interesting question, if we are creating 1 L of alcohol, why don’t we see a volume increase as a result of fermentation? When you add rum to a Coke, it certainly seems like it would have the same effect on the volume as adding an equal amount of water. It turns out that when you mix equal parts water and ethanol the volume increases only 1.92 fold. So we’ll only get 92% of the increase from adding the ethanol, .92 L in this case (close enough that we don’t notice a difference mixing spirits with water-based drinks).

If we simply added the same 1 L of pure ethanol to our 20 L of 1.050 wort, we'd have a resulting density of ((.789*1)+(1.05*20))/20.92 = 1.042. So the addition of alcohol is not itself enough to account for much of the drop in gravity we see during fermentation.

In a fermentation we aren’t just adding alcohol, so we’d also need to consider the reduction in volume from the sugar that is fermented (1.544 kg in our case - the sum of the CO2 and ethanol created by our hypothetical fermentation). I couldn’t find similar numbers for maltose, so I’ll treat this sugar as if it were sucrose. When you dissolve sucrose in water, approximately 54% of the volume is added to the volume of the solution. Sucrose weighs about .869 kg/L, so our 1.544 kg of sucrose would take up 1.778 L dry, the loss of which from the wort would result in a .960 L decrease in its volume).

So the loss of volume attributed to the destruction of sugar (.96 L) during fermentation completely cancels out the volume gained (.92 L) from the resulting ethanol, which is why we don’t see a noticeable volume increase (or decrease) during fermentation!

When trying to determine the ABV of a sour beer specifically, there are four other factors you might consider.

1. Highly acidic beers are around 1% lactic acid. As the formation of lactic acid doesn’t directly lead to anything entering or leaving the fermentor, we know the mass of the beer will remain constant regardless of how much lactic acid is created. Any change in the beer’s density would purely be the result of a change in the total volume.

1 molecule of glucose goes to create 2 molecules of lactic acid in homofermentative lactic acid production. Glucose has a density of 1.54 g/ml, and a molar mass of 180.16 g/mol. Lactic acid has a density of 1.2 g/ml and a molar mass exactly half that of glucose, 90.08 g/mol (which makes sense). In a 20 L batch of beer, 1% lactic acid by volume, would be 200 mL of lactic acid. The equivalent of 240 g of lactic acid, or 2.66 mol. This would require the fermentation of half that number of glucose molecules, 1.33 mol, which is 155.59 mL.

If we assume glucose behaves similarly to sucrose when dissolved in water, the loss of wort volume attributed to 155.59 mL of glucose converted to lactic acid would be 84.02 mL. I can’t find a number for what happens to volume when you mix lactic acid and water, but even if we assume the entire volume of lactic acid goes to increasing the beer’s volume, we’d be increasing the volume of the beer by 115.98 ml, just .58%. This is the equivalent of causing the 5% ABV calculated to be .03% too high (the larger volume with the same mass would indicate a more substantial reduction in gravity than would have been actually caused by alcoholic fermentation).

2. Acetic acid production by either Acetobacter or Brettanomyces consumes a molecule of ethanol along with a molecule of oxygen. This reduces the alcohol content, but also raises the mass slightly as the oxygen comes from the atmosphere. It seems like without the carbon atom of the CO2 released during fermentation the gravity would rise slightly less than what is lost during fermentation, causing an infinitesimally small over-estimate of the ABV. Acetic acid is legally limited to.15%, so it shouldn’t play a major role anyway (even if flavor wasn't a consideration).

3. Ester formation by Brettanomyces could have a small impact on alcohol content because esters are formed by combining an alcohol with an acid (e.g., ethyl lactate is a combo of ethanol and lactic acid). However, all of these are present in parts per million at the most, making their presence too low to substantially impact ABV calculations.

4. While not specific to sour beers, evaporation from a barrel reduces the amount of both water and ethanol a beer contains. As ethanol has a lower boiling point than water, it would tend to evaporate at a faster rate. The humidity in the room apparently plays a role in the relative evaporation rates as well (higher ambient humidity reduces the evaporation rate of water). At 70% humidity, the loss of alcohol and water is supposedly about equal.

In relation to these various areas, when compared to the errors in calibration and measurement I don't think it is necessary to make special considerations for the ABV calculations of mixed fermentation sour beers. This has been one of those things I spend hours thinking about only to come to the conclusion that I was better off ignoring the whole thing.

That said, this isn't exactly my area of specialty, if anyone sees any issues with my assumptions, data, or math, please let me know! I'm sure I've oversimplified some things, like the sugars, or how a water molecule is added when some polysaccharides are split, but I think I'm close enough to prove the point.

Simcoe & Sons Pale Ale Tasting

After posting earlier this week about the IPA I have fermenting with Conan, it seemed like a good time to knockout the tasting notes for the American pale ale I fermented with the pitch initially. This is a beer in the “new” American mold of Hill Farmstead Edward, Half Acre Daisy Cutter, and Tired Hands HopHands. As my friend Nathan refers to them, aromatic pale ales. That is to say: hopped for gigantic aroma, without excessive bitterness. He’ll have his own version on tap at Right Proper when they finally open their doors in a few weeks.

Simcoe & Sons Pale Ale

Appearance – Hazy. Conan is not a flocculant yeast strain apparently. Blonde body supports a small, tight, snowy head with fine retention.

Smell – Ripe summertime peaches. Wow! One of the most unique aromas I’ve had in a clean/hoppy beer. This is the sort of nose I strive for. While I enjoy the “nose in the hop bag” effect that some hoppy beers exhibit, I’d rather get the volatile aromatics without all the vegetable matter.

Taste – Similar to the aroma, saturated with juicy peaches and apricots. To the point that I could probably pass it off as a fruited pale ale. The hops become more resiny through the sip, lingering as a firm bitterness. The malt stays out of the way for the most part, adding an ever so faint toastiness. Very bright, crisp, and balanced.

Mouthfeel – Medium body, doesn’t taste the 1.015 FG I measured it at. Carbonation is about where I like it, medium-ish.

Drinkability & Notes – Like a good Belgian beer the yeast combines, not with spices in this case, but with the hops to create a profile that is difficult to attribute to one or the other. I’m officially a Conan believer (although I want to try the other isolates out there). Interested to see if the IPA fermented with the yeast harvested from this batch exhibits a similar aroma, or if different hops radically change the perception.

Conan the IPA (and Yeast)

There are too many ale yeast strains to count. While they’re all members of the same species (Saccharomyces cerevisiae), they contribute a huge assortment of flavors and aromas. This is because over millions of fungal generations, brewers around the world have placed selective pressures on them based on their own preferences, process, and equipment. One strain that is rapidly gaining popularity is named Conan. Its sudden spike in popularity is in large part thanks to the reputation of a beer fermented with it, Heady Topper from The Alchemist.

Conan is rumored to have an English origin, and gained a foothold in New England thanks to its use by Greg Noonan at Vermont Pub & Brewery. The general description of the yeast is appealing, mostly clean, but with a citrusy/apricot character. A more flavorful alternative to the straight-ahead Chico strain (WLP001/WY1056) favored by many breweries for their “American” style beers.

Heady Topper is an IPA that is completely saturated with hop aromatics, while not being gratingly thin or overly-bitter. In a beer with that much aromatic punch, how much difference could the yeast possibly make? The amazing thing about aroma is that small additions can greatly influence the overall perception. For example, the same four oils account for most of the aromatic compounds in every hop variety, but small fractions of other compounds create each hop's unique impression.

In his book IPA, Mitch Steele reports that The Alchemist uses a relatively low pitching rate (less than a .5 million cells per ml per degree Plato), fermenting at 68 F for a few days then up to 72 F. Elsewhere it has been reported that as the generation count rises, the attenuation drops. This is a larger concern for craft breweries, as few homebrewers reuse yeast for more than a couple of generations. A yeast which requires a bit of special attention.

Several small yeast labs, including GigaYeast (GY054 Vermont IPA) and The Yeast Bay (Vermont Ale), have cultured the strain to allow us to pitch Conan without the effort of growing it from a can of Heady Topper. I got a vial of East Coast Yeast's version, Northeast Ale, and decided to try it in a pale ale, and then repitch into an IPA. For whatever reason, reports have been that the ECY culture isn’t as attenuative as many brewers expect it to be. I experienced only 71% AA in the pale ale, and have yet to take a final reading of the IPA. Luckily the pale ale doesn’t taste overly sweet or thick.

In his article Vermont Cult Clones in the October 2013 issue of BYO, Dave Green mentions that "[I]n my conversations with the brewers it was indicated that Conan is no longer the strain that is being used." However there isn’t an explanation of whether this means that The Alchemist is no longer using the original isolate because it mutated, or if they have switched to a different yeast strain. (Luckily down in the comments, Art filled me in on his conversations with the author of the BYO article and John Kimmich of The Alchemist. Apparently they are still using Conan for Heady Topper, it is Hill Farmstead that is no longer using Conan, something I wasn't aware they did in the first place).

The IPA recipe below was tossed together with what I had on hand. Apollo and Pacific Jade hops purchased for Modern Times test batches never brewed, and CaraRed left-over from my Red Rye IPA. I’ll be interested to see how it all comes together!

Conan the IPA

Recipe Specifics
----------------
Batch Size (Gal): 5.50
Total Grain (Lbs): 14.13
Anticipated OG: 1.075
Anticipated SRM: 5.0
Anticipated IBU: 74.8
Brewhouse Efficiency: 79 %
Wort Boil Time: 90 Minutes

Grain/Sugar
------------
85.0% - 12.00 lbs. American Pale Malt
7.1% - 1.00 lbs. Wheat Malt
3.5% - 0.50 lbs. Table Sugar
3.5% - 0.50 lbs. CaraRed
0.9% -  0.13 lbs. Sauer(acid) Malt

Hops
------
2.00 oz. Columbus (Pellet, 11.9% AA) @ 45 min.
1.00 oz. Apollo (Pellet. 13.00% AA) @ 0 min.
1.00 oz. Pacific Jade (Pellet, 11.00% AA) @ 0 min.
0.50 oz. Nelson Sauvin (Pellet, 12.00% AA) @ 0 min.
1.00 oz. Apollo (Pellet. 13.00% AA) @ -15 min.
1.00 oz. Pacific Jade (Pellet, 11.00% AA) @ -15 min.
0.50 oz. Nelson Sauvin (Pellet, 12.00% AA) @ -15 min.
1.00 oz. Apollo (Pellet. 13.00% AA) @ Dry Hop
1.00 oz. Pacific Jade (Pellet, 11.00% AA) @ Dry Hop
0.50 oz. Nelson Sauvin (Pellet, 12.00%) @ Dry Hop
1.00 oz. Apollo (Pellet. 13.00% AA) @ Keg Hop
1.00 oz. Pacific Jade (Pellet, 11.00% AA) @ Keg Hop
0.50 oz. Nelson Sauvin (Pellet, 12.00%) @ Keg Hop

Extras
------
0.50 Whirlfloc @ 15 min.
0.50 tsp Yeast Nutrient @ 15 min.

Yeast
-----
East Coast Yeast ECY29 Northeast Ale

Water Profile
-------------
Profile: Washington, Hoppy

Mash Schedule
----------------
Sacch Rest - 60 min @ 153 F

Notes
------
Brewed 11/3/13

Water 50% filtered DC Tap, 50% distilled. 6 g of epsom salt and 6 g of CaCl added total. 2 tsp of phosphoric acid added to the sparge water. Collected 7.5 gallons of 1.055 runnings with a fly sparge, then added the sugar.

Half aroma hops added at flame out, the remainder 15 minutes later. Did not start chilling for another 15 minutes.

Chilled to 70 F. Pitched 3/4 cup of loose slurry from "Simcoe & Sons Pale Ale." 45 seconds of pure O2. Left at 63F ambient to ferment.

Good fermentation by 12 hours.

10/9/13 Raised ambient temperature to 66 F to help it finish out.

11/11/13 Added half of the dry hops to the primary fermentor.

11/16/13 Added three droppers full of BioFine Clear. Dropped temperature to mid-50s to help clear before kegging.

11/26/13 Kegged with the remainder of the dry hops. Still pretty cloudy. Got down to 1.012 (84% AA, 8.3% ABV), happy to see it that low!

1/6/14 Tasting notes, the Pacific Jade (I suspect) added a spicy edge that doesn't mesh well with the fruitiness of the other hops and the yeast. it is still a pleasant IPA, but not my favorite batch.

Focus on Brewing pH - American Pale Ale

It seems like there is always some new aspect of my brewing process to focus on. Most recently it's been getting control of the pH of the wort. I thought I'd walk you through my standard process, and give you a few reasons why you might consider doing something similar. There are plenty of more in depth science-heavy reads out there, but I wanted to do something a bit more accessible.

A day or two before brewing, I use the EZ Water Calculator to make a game plan. I like this free spreadsheet because rather than take into account the SRM (color) of the beer, it uses your recipe, which more accurately predicts the mash pH. The spreadsheet allows me to determine how I'll treat my water. I usually aim for the low end of the pH range for pale beers, 5.3-5.4 when measured at room temperature, a bit higher for anything roasty.

In the case of this hoppy pale ale (and those like it), I prefer to use a combination of methods to lower the mash pH. To halve the ~80 PPM of pH raising carbonate in my filtered DC tap water, I dilute with an equal volume of distilled water. That way I'm not forced to add an excessive amount of salts or acid (either of which can harm the flavor of the beer) to lower the pH into the ideal range. Depending on your water profile, you might need no dilution at all, or an even higher percentage.

I know that some people like to think of the balance between sulfate and chloride as a ratio, but that isn't entirely accurate. Having 10 PPM sulfate and 5 PPM chloride won't have the same flavor impact as 500 PPM sulfate and 250 PPM chloride. Sulfate enhances the perception of bitterness, while chloride boosts body and the perception of sweetness. Normally I'd add gypsum for sulfate, but I was out, so I added  Epsom salt in addition to the calcium chloride.

While I'm heating up the mash water I'll weigh out the salts on a scale with a .1 gram resolution. Only half of the total calculated amount goes into the strike water, I save the rest for the sparge water. I usually leave out the acidulated malt from the grist initially. I'd rather take a pH reading and add the "right" amount if it turns out to be too high, rather than risk having to deal with a pH that falls too low. Municipal water profiles shifts throughout the year, so even a perfect calculator wouldn't always be accurate if it relied on a yearly average profile.

After mashing in, I allow it to sit for between five and ten minutes to allow the various chemical reactions that impact pH to occur (mostly calcium and magnesium reacting with phosphates from the malt lowering the pH). At that point I pull a sample, cool it in a clean/dry ramekin to around room temperature, and measure its pH with my just-calibrated meter (Hanna Instruments HI 98107). When this one dies I'll probably get one with a .01 resolution to get a bit more precision. pH strips aren't very accurate and tend to go bad quickly if not stored with a desiccant, but they are an option.

If the reading does not fall within my targeted range, I jump into action. If the pH is too high, this usually means adding acid malt (~1% of the grist for every intended .1 drop). I'd add additional salts only if I want more minerals and would have added them to the boil anyway. If the pH is too low I add chalk (which should ideally be dissolved in carbonated water first) or baking soda (which can be added directly to the mash).

Having a mash pH in the correct range helps the enzymes responsible for the conversion of starches into sugars, and also gets helps the pH to fall into place further down the line.

With the mash resting, I start heating the sparge water. Adding the reserved minerals, and enough phosphoric acid to lower the pH to under 6.0. Having a lower pH sparge is good insurance to prevent tannin extraction. This is especially important with a fly sparge, and even more so if you aren't monitoring the gravity of the runnings. Even if you batch sparge (like I usually do), acidifying the sparge will help you hit the ideal boil pH.

Having a boil pH around 5.1 enhances hot break formation (which helps produce a clearer beer) and creates a smoother hop bitterness. I know some brewers are more fanatical about this, but I tend to pull a single sample early in the boil, measure it and add acid if warranted. I'm too lazy to track it any more once I start adding hops.

If the pH is kept in line on brew day, and a healthy fermentation ensues, the finished beer’s pH should be in the ideal range (low 4s - flat, room temperature) by the time you are ready to keg or bottle. For a pale beer, having a suitably low pH gives it a crisp and refreshing balance. A low pH also improves the resistance of the beer to unwanted spoilage microbes. For darker beers I find that a slightly higher pH gives a more rounded mellow flavor, canceling out some of the sharper acrid charcoal flavors, shifting the roast perception to smoother coca and coffee flavors.

All of this gets easier as you go, learning what treatment works for your water and the types of beer you tend to brew. You can always experiment adding small amounts of acid to a glass of the finished beer to judge for yourself how it changes the perception.

This batch is pretty representative of where my head is at these days on hoppy beers. Not too strong or bitter, but with loads of saturated hop flavor and a big fresh nose. It was my first time fermenting with East Coast Yeast's North East Ale (apparently their isolate of Conan). Luckily early tastes are much better than my attempt to isolate the strain!

Also a reminder, if you use a plate chiller, recirculate hot water and PBW after flushing with water. I generated two gallons of this greenish water while cleaning up after this batch.

Simcoe & Sons Pale Ale

Recipe Specifics
----------------
Batch Size (Gal): 5.00
Total Grain (Lbs): 11.11
Anticipated OG: 1.058
Anticipated SRM: 5.1
Anticipated IBU: 56.0
Brewhouse Efficiency: 72 %
Wort Boil Time: 95 Minutes

Grain
------
85.5% - 9.50 lbs. American Pale Malt
9.0% - 1.00 lbs. Wheat Malt
4.5% - 0.50 lbs. Belgian CaraVienna
1.0% - 0.11 lbs. Sauer(acid) Malt

Hops
------
0.63 oz. Columbus (Pellet, 11.9%AA) @ 60 min.
2.5 ml HopShot (Extract) @ 60 min.
2.01 oz. Mosaic (Pellet 0.00% AA) @ 0 min.
1.75 oz. Simcoe (Whole 0.00% AA) @ 0 min.
2.00 oz. Citra (Whole 10.00% AA) @ Hop Back
1.25 oz. Simcoe (Whole 14.00% AA) @ Hop Back
.625 oz. Citra (Whole, 10.00% AA) @ Dry Hop (Primary)
.625 oz. Mosaic (Pellet, 10.00% AA) @ Dry Hop (Primary)
.75 oz. Simcoe (Whole, 14.00% AA) @ Dry Hop (Primary)
.625 oz. Citra (Whole, 10.00% AA) @ Keg Hop
.625 oz. Mosaic (Whole, 10.00% AA) @ Keg Hop
.75 oz. Simcoe (Whole, 14.00% AA) @ Keg Hop

Extras
-------
0.50 Whirlfloc @ 15 min.
0.50 tsp Yeast Nutrient @ 15 min.

Yeast
-----
East Coast Yeast - ECY29 North East Ale

Water Profile
-------------
Profile: Washington, Hoppy

Mash Schedule
-------------
Sacch Rest - 60 min @ 153 F

Notes
-----
10/15/13 Made a 1.25 L stir-plate starter for the month old yeast vial.

10/16/13 Brewed by myself

Mash water filtered DC tap cut with 50% distilled. Added 3 g of Epsom Salt and 3 g of CaCl. Same deal for the sparge water.

Mash pH = 5.5 at room temperature. Added 1% acid malt to lower the pH to 5.4

Acidified batch sparge water with 2 tsp of phosphoric acid.

Collected 7.5 gallons of 1.044 runnings.

Bitter with 1/2 a HopShot, plus the Columbus.

0 min hops were allowed to hop-stand for 30 minutes.Couldn't get good flow through the HopRocket, so after the first gallon or so, so I dumped the hops back into the kettle along with the trapped wort, and went directly to the plate chilled. Got it down to 70 F.

45 seconds of pure O2, and pitched the whole starter. Left at 64 F to ferment.

Increased to 68 F after three days.

10/20/13 Dry hopped in primary with .75 oz Simcoe, and 5/8 oz each of Citra and Mosaic (2012 harvest). Fermentation appears mostly complete.

11/3/13 Racked to a flushed keg with the same amount of dry hops again (2013 harvest). Only got down to 1.017 (71% AA - 5.4% ABV), but it tastes much drier. After calibrating my hydrometer, it turns out it actually finished at 1.015 (74% AA - 5.6% ABV), which makes a bit more sense.

11/21/13 Tasting Notes. Amazing peach character thanks to the combination of yeast and hop aromatics. Despite the lackluster attenuation, doesn't come off sweet.

North Carolina IPA Tasting

I’ve brewed more IPAs than any other style (so long as you don’t consider “sour beer” to be a style). My standard recipe template is yellow to pale-gold, with a malt bill that gets out of the way of an aroma-drenched hop bill. Sometimes it’s nice to be kicked out of my rut though, so I played along with the Riverbend Malt House Homegrown IPA kit. It included some of their darker grains (similar to Munich and Chocolate), but no crystal malt, so it avoids being sticky sweet.

The hops ended up being all-Chinook after I tossed the less-than-great smelling whole Cascades from Echoview Farms (they have some pelletized Nugget hops available now on their website).

North Carolina IPA

Appearance – The amber-golden body is towards the hazy end of the IPA spectrum, but still appealing. A few weeks in the keg has really cleared this one up. The white head is luscious, creamy, dense, and long-lasting.

Smell – Bright, but not overwhelming, resiny hop aroma. Grapefruit and pine mostly. The grainy malt comes through well, more East Coast than West Coast (unsurprisingly). The US-05 adds its slightly peachy edge, especially as the beer warms. A bit restrained as far as my IPAs go, but probably hoppier than half of the commercial IPAs I try.

Taste – Well balanced. Malty without being sweet. Hoppy without being harshly bitter. The hop flavor is well saturated, thanks to the bonus 5.5 oz of Chinook I added on the hot-side, but the North Carolina hops carry the aroma nicely. Clean otherwise, no issues with the fermentation or sanitation.

Mouthfeel – Medium body, not quite as crisp as my standard IPAs, but that certainly isn’t a bad thing in a beer like this that has more malt character. Medium-low carbonation, judging from the pour rate I think the dry hop sock is partially covering the dip-tube. I won’t do anything about it unless it gets worse.

Drinkability & Notes – I’m pleased with the way this batch turned out, but that took a bit more effort on my part than a kit recipe ought to. I’ll give both products a tentative recommendation, but I'd be hesitant if you couldn't inspect them before purchase.

Sour Experiment #1 - Two Week Sour

One of the most annoying (and intimidating) aspects of brewing sour beers is how long they take to ferment. Sure there are shortcuts, like sour mashing, but rarely do the results approach the nuances of long-aged mixed-fermentation beers. One of the last things I did while I was at Modern Times in August was to taste the four versions of a beer I brewed with an experimental souring technique two weeks earlier.

Souring a beer before the alcoholic fermentation is a good idea, but a sour mash presents three major issues:

1. After souring the mash, it can be difficult to separate the wort from the spent grain.

2. Exposure to air during souring can lead to the growth of unwanted aerobic microbes that produce off-flavors.

3. Allowing the pH to drop too low can cause fermentation issues for most ale yeasts.

To remedy problem #1, I dipped into my bag of tricks and pulled out the sour worting technique I used a few years ago. After a single-infusion mash, I collected the reddish wort and heated it in the kettle to near boiling to ensure any microbes from the grain were dead. With this method the wort is drained with a standard temperature and pH, so there are no issues lautering as usual.

To address problem #2, I ran the wort through the plate chiller (aiming for 115F), and into four plastic carboys, each of which had been flushed with carbon dioxide (back at home I miss the plumbed CO2 lines at the brewery). Flushed kegs would work equally well.

To achieve the acidity, I pitched one carboy each with a starter of Wyeast Lactobacillus, a starter made from the microbes living on pale malt, a starter from the microbes living on acid malt, and a small hop-sock of crushed acid malt. For the grain starters I followed a similar protocol to the one used for that previous sour worting batch. My goal was to determine which of these microbial sources produced the best results.

To maintain the temperature in Lactobacillus’s ideal range, I placed each carboy in one of the pilot system’s vessels, filled with 120F water. At the start and end of each day for three days I removed the carboys, reheated the water, and replaced them. I also insulated the rig with blankets to help maintain temperature. Usually they'd be down to about 100F by the time I reheated. I didn’t have room for the fourth (pale malt starter) so I left it under the blanket.

The results were surprising. After three days, the least sour of the bunch was the Wyeast Lacto, clean and pleasantly tart. The two grain-starters were next (despite the temperature difference), they were still clean, but a bit more lactic. The grain bag was the most acidic, but also had a slightly stranger aroma that was more in line with what I expect from a sour mash but luckily not as cheesy or intense. With acid production complete (pH 3.4-3.5), I boiled each in turn with a small dose of hops and yeast nutrient. During each boil I cleaned and sanitized the fermentor, refilling it with 68F wort post-boil.

To resolve problem #3, rather than fermenting with pH sensitive Saccharomyces, I opted for a 100% Brett fermentation with the BSI Brett Drie we had on hand for production brews of Neverwhere, Roraima, and Southern Lands. Brett works quickly at a pH as low as 3, and produces interesting flavors too.

My last day working in San Diego I racked each of them to a Corny keg, and shook in carbonation. The pale malt starter and the steeped acid malt were my favorites. Each had a nice acidity with a pleasant Brett character. I had skipped boiling the Wyeast Lacto portion and the result was a subtle raw graininess similar to what I taste in my no-boil Berliner weisses. The acid malt starter had an unpleasant aroma not present before the Brett fermentation, just sort of rough. With that interesting range of characters, we decided to blend the three we liked to make 15 gallons of beer to serve at the Tasting Room Grand Opening.

Reviews were mostly positive on Untappd, "I'm not one for sour beets, but this is fantastic! Tickles the taste buds in the back of your mouth in just the right way." - Stephanie P. "Had it 3 times so far might get another" - Heather H. Both included pictures of the finished beer as well, something I never got to see for myself!

I had a beer at GABF from TRiNiTY Brewing (7 Day Sour) that used a similar technique, but fermented with a mixture of Brett strains post-kettle-souring. The result was terrifically funky, and brightly acidic. I think I’ll have to try something similar, integrating a strain like Brett Drie/Trois which ferments quickly, with others that produce more classic Brett aromatics.