Culturing Yeast

There comes a time in every brewer's life when you just want to do something different. You've experimented with different yeasts, malts, hops, and styles of beer. What comes next? Well, for me it was going a step further than just making my own beer, and experimenting with growing my own yeast. Sure, yeast is cheap to buy, but why not try to culture my own?

One of my pet peeves about American breweries is that there don't seem to be many who make a good, German-style Hefeweizen. Hefeweizen is a notoriously difficult style to brew, both for amateurs and professionals. I've only ever had two Hefeweizens in the US that tasted anything like German Hefeweizen. One was at Bootlegger's Brewery in Fullerton, the other was a Dunkelweizen at Bluejacket in DC.

For homebrewers like me who prefer to use dry yeast, there really aren't too many options for brewing Hefeweizen. I tried Danstar Munich and Safale WB-06, but neither one really provided the flavor I wanted. And I really don't want to experiment with liquid yeast, because the descriptions of their flavor profiles are all over the map. And of course, it doesn't help that brewing advice for Hefeweizen is all over the place too. Some say that if you want the nice, banana-y flavors that you have to keep it cool, while others say it needs to be warm. What to do?

My favorite Hefeweizen is Paulaner, and my favorite Weizen overall is Aventinus Weizenbock by Schneider. The good think about Hefeweizen is that it always has yeast in the bottle, hence the "Hefe" part of the name. In Germany, if you're pouring a bottle of Hefeweizen, you pour out all but a fingerful of beer into your glass, then roll the glass really fast between your hands to stir up the yeast on the bottom, then pour it into your beer. That yeast at the bottom, assuming it's the same strain used at fermentation and not added specifically for bottle conditioning, can be a source for valuable yeast cells that can be cultured to create your own yeast colony.

According to everything I read online, Schneider was one of those breweries who bottle their Weizenbier with the same strain used in fermentation. So buying a few bottles of Schneider should allow one to culture their Hefeweizen yeast. I went ahead and bought three bottles of Aventinus and one bottle of regular Schneider Weisse to try to culture the yeast.

I already had a one-liter Erlenmeyer flask that I had purchased with the intention of using it to culture yeast. In order to provide a good wort in which the yeast could grow, I purchased one pound of light wheat, with the intent to make four ever-stronger batches of wort. The hops I used for their antibacterial properties were Magnum hops off the vine in my backyard (the subject of a future post.)

The first batch of wort I made by crushing two ounces of the light wheat, adding to a quart of water, and heating to 150F. I covered it and checked the temperature every 15 minutes, heating back to 150F if the temperature had fallen. I periodically took small samples of the wort, put them in a glass, and added one drop of iodine to see whether or not the starches had converted. Iodine will turn blue in the presence of starch, but will not change color when no starches are present. Because this batch of wort was so thin, it took over an hour for conversion. Once the starches were converted, I strained the solids out of the liquid and boiled the wort with a few hops cones for 60 minutes. By that time the gravity of the wort was around 1.026, fairly weak, which is a good thing for yeast cells that might be strained from the combination of high alcohol levels in Aventinus and the unknown conditions of transportation and storage.

I poured the hot wort into the Erlenmeyer flask and then placed the flask into a tub of cold water, stirring the flask around to let as much heat escape as possible. Within 15-20 minutes, the wort was cooled to below 80 degrees, thus making it safe to add yeast. After finding a couple willing volunteers to help me consume the contents of the Aventinus and Schneider Weisse bottles, I quickly stirred up the yeast at the bottom of the bottles and poured the yeast slurries into the Erlenmeyer flask. I capped it with a universal bung (which was too small; you need to get a properly sized rubber stopper), added an airlock, and set it on the counter to watch it work.

By the next day, I still hadn't seen much activity. Then I remembered that I had forgotten to add yeast nutrient and yeast energizer into the wort. Doh! If you're trying to culture yeast from such small samples, every little bit of help is needed. So I quickly boiled a small amount of yeast nutrient and energizer and added it to the flask. Voila! Within a few hours I had a very vigorous fermentation.

For the three subsequent batches of wort, I used three ounces, five ounces, and six ounces of wheat respectively. Because of the increased absorption of water by larger amounts of malt, volumes were a little lower in the subsequent batches. The final batch I boiled for only about 45 minutes because I was facing a time crunch, and the starting gravity was around 1.046, roughly what the starting gravity of a standard Hefeweizen.

I cooled the wort in these subsequent batches by covering the pot 15 minutes before the end of the boil to sterilize the cover and then placing the pot in a tub of cold water in the sink. I changed the water once and just let the pot sit covered. After about an hour, I sanitized my temperature probe (also the subject of a future post) and measured a temperature of less than 80 degrees. I then poured off most (not all) of the existing wort and added the new wort to the flask. Make sure to taste some of the old wort. If you have an infection, or if wild yeasts have taken hold, you'll be able to taste it and toss the yeast and start over with a fresh batch. Better to lose some of your yeast culture than to find out after five or more gallons of beer that you have a yeast infection.

If you take a look at the second photograph, taken during fermentation of the final batch of wort, you can see the yeast and sediment at the bottom of the Erlenmeyer flask. I'm still probably a little on the light side in terms of the number of yeast cells I have in that flask, but I've never been one to be afraid of underpitching. A little yeast nutrient in the wort and I should be just fine. Not too much longer now before I get to test this yeast in a five gallon batch and see if it provides the German Hefeweizen flavor I've been looking for.

Equipment Review: Big Mouth Bubbler

Big mouth carboys came out a while back, intended to help homebrewers who dry hopped. With the normal, narrow-necked carboys, dry hopping was very difficult. I've never dry hopped in bags, so I always poured my pellets down the neck of my carboy. The idea of trying to fill a hop bag and stuff it down a carboy neck always struck me as ridiculous. Enter the big mouth bubbler.

The mouth is nice and big, allowing you to get your entire hand and arm inside the carboy. I still went ahead and hopped with loose pellets rather than using a hop bag, but if I ever dry hop again, I think I'll use a bag. Much less likelihood of getting hop residue in the finished beer. The price of these carboys is about the same as normal carboys, and I've read that Korean supermarkets in California sell them for about half of what you'd pay in a homebrew store. I wouldn't be surprised if these were originally intended to be for making kimchi, and some enterprising homebrewer saw a use for them in brewing.

PROS:

• Makes dry hopping much easier.
• Wide mouth allows arms to get inside carboy, so that it can be used for other things like winemaking, or fermenting kimchi and sauerkraut.
• Much easier to clean than normal carboys. Can wash by hand, no need to use bristle brushes.
  

CONS:

• Requires a harness to carry it when full.
• Requires periodic replacement of the lid gaskets.
• Lid tightens very securely, which can make it difficult to unscrew, especially with wet hands.
• Slightly wider than normal carboys, takes up more floor space.
• Requires a smaller stopper than the universal stopper used for normal carboys - if you don't have that size on hand, you'll have to buy new stoppers.

Adventures in Barrel Aging

I'm going to take a brief detour from brewing discussion and talk about my experiment with small batch aging of spirits. For those of who live in areas where it's impossible to distill liquor ourselves, this means purchasing the cheapest, highest-proof alcohol possible from the liquor store, placing it in a small charred oak barrel and letting it age for a few months. The theory is that, because the amount of barrel interior surface area per amount of liquor increases as the barrel size decreases, a smaller barrel could produce in a few months a comparable spirit to what would take years in a standard-size (42 gallon/159 liter) barrel. So I decided to buy a 2 liter barrel and try my hand at improving rot-gut spirits. The 2L barrels are available online for anywhere from $40-60 shipped.

I started by filling my barrel with hot water and letting it sit for a day to ensure that the wood would absorb water and expand, thus ensuring a leak-free experience. Then I filled the barrel with as much 100-proof vodka as I could. It turns out that my little 2 liter bottle had a capacity of about 2.3 liters. And then it was just a matter of remaining patient while the spirits aged. Within a couple of weeks there was already a noticeable improvement in flavor of the vodka, as well as a definite change in color as the liquor darkened from contact with the charred interior of the barrel. The flavor was also very oaky, as you would expect from a new barrel. After about two months in the barrel, I decided to pull the vodka and age some rum, a mixture of both standard proof and 151-proof rum. The 2.3L of vodka had, through evaporation, been reduced to about 1.5L. The angels certainly took their share!

The rum was aged for close to three months and it also improved greatly in taste, but by this point the spigot on the barrel had started to leak pretty severely, so I purchased some replacement spigots. I then pulled the rum, with the idea of aging it again later, and decided to make some Madeira. From a little over two liters of rum I ended up with about 1.25L.

For the Madeira, I used one bottle of Charles Shaw Sauvignon Blanc, one bottle of Charles Shaw Chardonnay, and 600mL of the cheapest American brandy I could find. I placed the barrel out on our sun porch, as I had with the previous agings, and largely forgot about it until about two months into aging. When I checked on the barrel, mold was growing around the bung and all over the spigot, so I cleaned those areas off with vodka and monitored for a few days. With no more mold growth, I thought I was out of the woods. That is, until I checked back a few weeks later and found fruit flies swarming all around the barrel. I had previously tried to seal the spigot leak with beeswax, unsuccessfully. However, that beeswax gave the fruit flies a place to lay their eggs, so I found dozens of larvae all over the wax. Not only that, but because the spigot is wood and therefore porous, the wine had penetrated all throughout the spigot. And because wine, unlike liquor, still contains residual sugars, it is even more attractive to fruit flies than liquor. Judging by the vinegary smell coming from the spigot, the fruit flies had been having a good time drinking the wine that had made it to the surface of the spigot.

Because I couldn't risk acetobacter contamination of the Madeira, which would turn the wine into vinegar, I pulled it and bottled it into wine bottles, then replaced the spigot yet again. This new spigot I couldn't get to stop leaking. If the barrel is level, the spigot will leak a shot of liquor in about 10-15 minutes. If I tilt the barrel at about a 30 degree angle I can slow the rate of leakage, but not stop it completely. This is even after filling the barrel with boiling water to ensure that everything is expanded. I put some cheap Scotch into the barrel and, after a week, there's a little puddle on the floor of the sun room, with fruit flies all around. So, I think my little experiment may be over. I had hoped to use this barrel for making vinegar once I was done with spirits, but because of the leakage I don't even trust it to do that. Unless I can get the leak to stop, I'll pull the Scotch and use the barrel for firewood.

For the amount of money I sunk into the barrel, replacement spigots, shipping, and cheap liquor, I probably could have bought myself a bottle of Angel's Envy and a bottle of Lagavulin 16. Instead, I'm left with about a gallon of assorted spirits that are one or two levels up from rot-gut. Maybe good for mixed drinks or eggnog, but not really what I would choose to pour myself a dram of on a cold winter night. I won't call it a failure, since it was definitely a learning experience, but I don't think I'll do this again, unless maybe I can find myself a better cask, one without a spigot. I also now know, from the experience with the Madeira, that I won't be barrel aging any of my beers unless I can find a cask with solid heads.

PROS:

• Liquors that are undrinkable out of the bottle will improve markedly. Flavor becomes smoother and they can actually be sipped without gagging.

CONS:

• Small barrels are made of much thinner wood than larger barrels, thus minimizing the amount of liquor that can be absorbed into the wood pores while also increasing the amount of evaporation through the wood.
• Spigots are very difficult to get to stop leaking. Better would be a small cask with solid heads and only the one bung hole up top.
• Porous nature of spigots will lead to their becoming soaked in liquor, thus attracting mold and fruit flies.

Brewing Primer Part 6 of 12: Boiling Wort

Boiling the wort is necessary to kill any wild yeasts or bacteria that could outcompete beer yeast and spoil the beer. It goes hand in hand with hopping, since most hops will be added in the boil, but that will be covered in the next section.

Boiling wort also drives off dimethyl sulfide (DMS), a compound that forms corn- or vegetal-tasting compounds in the beer. Most worts will be boiled for at least 60 minutes to drive off DMS, but can also be boiled longer. Worts using Pilsner malts are recommended to be boiled for at least 90 minutes since the lightly-kilned malt contains higher amounts of DMS precursors than other malts. Boils should also be uncovered, otherwise DMS that is boiled off will accumulate in water droplets on the lid and fall back into the beer.

When boiling wort, you need to take into account your boiloff rate, the rate at which water evaporates during the boil. Since you'll want to end up with 5 gallons of beer (or whatever size batch you're targeting) you need to ensure that you have a sufficient amount of wort to begin the boil. For the most part you'll have to figure this out through trial and error, but there are some steps you can take to make it a little easier. The first thing you'll want to do is find out your boiloff rate, the rate at which your wort evaporates as you boil it.

In order to find out your boiloff rate, you first need to know the volume of your boil kettle. For a 5-gallon batch of beer I recommend at least a 10-gallon boil kettle, otherwise you'll risk a boilover when your wort gets up to boiling temperature. Cleaning up sticky, scorched wort from your stovetop is not fun, it smells pretty bad, and it wastes a lot of what could have been good beer.

Back to calculating the boiloff rate. Fill up your boil kettle with a known amount of water, say 5 gallons. Or fill it with 7-8 gallons, since that's how much wort you'll likely be adding when you brew. Measure the depth of water with a ruler, along the side of the kettle. That gives you a rough conversion for the number of inches or centimeters in the kettle per gallon of water. Then bring the water to a boil. As you pass through the 140-150 degree range, which is where your wort will be when you put it in the kettle, measure again. Water expands as it heats (online calculator to calculate thermal expansion here), not by a lot, but you should take that into account.

Once you're at a good rolling boil, measure the depth again. Boil for 30 minutes and measure the depth again. Repeat this after another 30 minutes, and then again after another 30 minutes, just to make sure that your water boils off at an even rate over the 90 minutes of a possible boil. And if you're really picky, you can even let the water cool back to room temperature and measure the depth again, as a final check. These numbers don't need to be 100% accurate, 98% is fine, as we're dealing with volumes so small that a few ounces of water here or there won't make too much of a difference. You just want to be in the general ballpark. And after a few batches you'll have done enough trial and error to be able to dial things in pretty well.

A 10-gallon boil kettle is large enough that you'll probably need to use two stove burners to get your wort up to boil in a decent amount of time (less than 30 minutes). It helps to know the BTU output of each of your burners. The stove I started on had 4 burners, each at 10,000 BTU rated output, and the grates were fairly low so that the kettle was pretty close to the flame. We just got a new stove a few months ago, with one "turbo" burner rated at 15,000 BTU, one diagonally across from it at 12,000 BTU, and two simmer burners at 5,000 BTU. The new grates make it easier to move the kettle around, but they sit much higher off the flame, which I'm certain leads to significant heat loss. Even using the 15K in combination with a 5K, I have to cover the kettle in order to get it to a boil. And instead of the roiling, rolling boil I had before, I get what looks to be barely a simmer. The benefit is that because the boiloff rate is significantly lower for the new stove, I don't need to use as much water when I sparge. So instead of targeting 8 gallons of wort to begin the boil, I now only need about 7 gallons.

Now that you have your boiloff rate you can figure out how much wort you need to start off with. I keep a detailed spreadsheet of each of my brews, and I calculate the amount of water lost to grain in the mash. Normally it's between 0.115 and 0.125 gallons of water lost per pound of grain you use, but some grains absorb more water and some less. I measure the amount of wort in my boil kettle with a ruler to see how many gallons I've ended up with, and adjust accordingly from brew to brew if I start noticing discrepancies. I have a boiloff rate of 5/6 gallons per hour, or 1.25 gallons over the course of a 90-minute boil. I also generally leave a lot of my trub (sediment) at the bottom of the kettle, so I estimate some loss there. Once fermentation begins I estimate even more loss as the yeast reproduces and absorbs water. And when I transfer and bottle the beer I'm not able to get every last drop out of the carboy, so I estimate 3/4 to a full gallon of liquid loss over the course of that whole post-boil process. In order to end up with 5 gallons of finished beer, I need to account for 2-2.25 gallons of water lost throughout the entire process, meaning that 7 gallons of wort is the bare minimum I need to start with.

With regard to sediment after the boil, you'll have hot break, cold break, and hop solids. Hot break are proteins that coagulate as the wort heats up to a boil. You'll notice the wort starts to get a foamy head as it heats up. This foam expands until the boiling point is reached, at which point air bubbles pierce the foam and the head collapses. This is why you need to use a large kettle, especially if you're covering it while heating, because you don't want this foam or any of the wort to boil over and create a mess.

Once the boil has been reached you will often see little bits of protein solids all throughout the wort. Very often it almost looks like egg drop soup. You'll get even more proteins coagulating once the wort is cooled. And of course when you add your hops, they will absorb water and you'll be left with hop residue at the bottom of your wort. But I'll cover all of that in the next couple of chapters on hopping and wort chilling.