YeastCulture

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Yeast Culture for Dummies

Here are some of the means we've used over the years for culturing our yeast. We have since returned to using the dregs from a regular bottle of brew since it is effective and requires no extra work really, unless you keg. See the links below for lab-grade culturing tutorials.

Materials Nothing Culture FAQ Like A Pro Almost Pro The Rest of Us

Materials for Culturing

When culturing your own yeast, depending upon which method you use, you will need some special materials. Although some methods require nothing more than beer bottles and a cigarette lighter, other methods require special laboratory equipment. One good source of this special equipment is the Yeast Culture Kit Company. Another good source would be your favorite laboratory supply house. There are a few good places listed in the Brewing Yeast Stock FAQ, as well.

Instead of petri dishes, however, one can substitue 125ml (1/2 cup) mason jars. The only disadvantage of these is that they take up more space than a petri dish. Otherwise, however, they'll serve the purpose admirably. The same mason jars can also be used instead of testtubes, saving even more money.

Like a Pro

The Brewing Yeast Stock FAQ, written by Pete Womack and HTML'ized by Alan, gives in-depth details on how to maintain your own yeast bank. Almost Like a Pro

Here's a really nice method given to me by Jim Overstreet. Note that some agar (like the stuff I just bought) comes in flakes. In this case use 4 to 6 Tablespoons of flakes per litre (quart) of wort. Also note that tiny 125ml (1/2 cup) Mason jars can be used instead of the baby food jars. Of course, the baby food jars are cheaper (unless you count the cost of the baby, itself ).

Thanks a lot, Jim.

-Alan Using Baby Food Jars for Cultivating Yeast

The current price of new culture tubes in bulk is over $3.50, and these are fairly small tubes to boot. Also, you are usually required to order in very large quantities to lessen the "sticker-shock" price. By using baby-food juice jars, Pedialite jars, etc you can make the process of yeast culturing a fairly inexpensive affair. Actually, any small glass jar with an autoclavable vacuum-sealable lid will work.

First step is to locate a neighbor or relative with a new baby, and ask them to save the juice/food jars for you. Depending on the previous contents of the jars some are better than others, due to the fact that some will pick up the odors of the previous contents. I try to use the juice jars if I have to buy them, as you can drink the juice, and have a good culture jar for under .25 cents. Stores regularly run specials of 4/$1.00 to 6/$1.00. The brewmaster at a local brewery uses Pedialite jars, which he says are designed to be autoclavable.

Second step, is to locate the culture medium. I use a mixture of wort, agar and yeast nutrient. Wort is easily obtained by making an extra gallon or two during your next brewing session, use 1 quart for the medium, and the rest for canning starters. Yeast nutrient can be obtained by mail order, and it is a white rock-candy like substance (diammonium phosphate),you only need 1/8 tsp of this, and it's not absolutely necessary. Wort should be of normal gravity, say 1.040 and clear of trub/bugs/hops. You could also make this from extract or dme. Agar is best obtained at a Chinese grocery store. It comes in a clear pack similar to spaghetti, but the agar looks like spaghetti-sized clear strings of cellophane. My pack was labled in Chinese, but had "AGAR AGAR" in English on the label. It is put up by Hang Loong Marine Products in Hong Kong, weight is 4 oz (a lifetime supply), cost $3.00. Compare this price with agar purchased at a lab supply house.

Your culture jars should be absolutely clean. I use a solution of ELECTRASOL dishwashing detergent (available in bulk at wholesale clubs) and perhaps a little bleach in very hot water. Let the tops and jars soak, then rinse in hot tap water, then set aside to dry. After drying, discard any with lids that retained a smell or show signs of bacterial infection (black marks inside the lid). After drying upside down, cover and place on shelf somewhere till you are ready to make the "slants". Technically, it will not be a slant, as the jar will not be lying on it's side (usually done in narrow tubes to increase surface area).

Place the quart of clean wort in a stainless pot, an slowly heat. While heating, take about 10 to 15 of the Agar strings, and cut them in small pieces into the wort. Continue heating till a very slow boil, continue stirring as the agar is somewhat difficult to dissolve. Keep boiling and stirring, and as soon as agar is dissolved, take a tablespoon of the mixture and pour it on a cold dish or plate. Wait till it cools to room temperature, and see if it jells like a good firm Jello. If not, add another 5 strings of the agar, and try again, till you get a firm jell. Maintain a very slow boil in your pot.

Next, line up your super-clean sanitized and covered jars, and you will place enough of the medium in the bottom of each jar to a depth of about 1/16", just enough to totally cover the bottom. Cap immediately, and continue till all jars are finished. Excess mixture can be placed in a super-cleaned pint/quart jar with lid that is capable of being autoclaved. This will be used for further culture sessions. This residue should be placed in pressure cooker, and autoclaved at 15 psi for at least 15 minutes. You shoud place about 1 to 2 tablespoons of white vinegar in your pressure cooker water to prevent the carbonates from clouding your glass. When finished, let this come to room temp, then keep this bulk medium in the fridge for further sessions.

Each of the culture jars has to be autoclaved to provide a sterile medium for inoculation. Place the caps on the jar, but not super-tight, just firm. Place these into your pressure cooker, and give them the same treatment you gave the bulk medium, 15 psi for 15 - 30 minutes. Remove heat, and allow to come to room temp. These sterile "slants" will be your growth medium.

When ready to inoculate, you will need a swollen pack of yeast, some 70% rubbing alcohol, clean paper towels, and a 1 cc or so hypodermic needle (find a diabetic for the disposable type or you can purchase a glass autoclavable one at drug store). Float the yeast pack in a bowl of water containing a fairly strong solution of bleach, along with the scissors you will use to cut open the yeast pack. Let this soak for 15 minutes or so. Have alcohol, paper towels, slants and any flaming device all handy in a clean, non-drafty environment. Some people work inside a glass aquarium which has been sprayed with Lysol or some alcohol to minimize chances of contamination. I have devised a "paper-towel-septum" method which seems to work pretty good for me, but it's a bit messy.

Next step, you have to cut open the yeast pack, about 1/2 way down the pack, so you can easily get the sterile hypodermic in to slurp up some yeast. Shake the pack vigourously before opening, to try to distribute the yeast "paste" throughout the wort. 4 hands are better than one for the inoculation step.

Soak a paper towel in 70% alcohol, then thoroughly wipe/saturate the slant jar and leave covered for a minute or so, to give the alcohol time to work. Keeping the jar covered with the paper towel, open the jar, wipe the rim/cover, place cover down. Stretch the paper towel over the jar mouth, insert the needle through the towel into the jar, and spray about .1 cc of wort onto the agar medium, while moving the needle around to distribute the wort. Remove needle, pick up the cover, then tightly cover the jar, all the while keeping the whole thing under the alcohol-soaked paper towel. In effect, you are making a minature "hood" to help keep airborne contaminants out of the jar. This proceedure is kinda messy and takes a little practice, but common sense is the order of the day. Just try to keep the yeast pack covered when you are not slurping up wort, and keep everything in the near vicinity as sterile/sanitized as possible.

After inoculating all the slants, place them on a dark shelf for about 3 days or so to multiply. After 24 hours you will see the creamy white paste forming on the medium, you can swish it around to make sure the entire medium is covered. After a few days, before refrigerating, take each jar, wipe with alcohol soaked paper towel, keeping the jar completely covered with the towel, crack the lid open very slightly till you hear a slight hiss (allowing the built-up CO2 from the fermenting medium to escape), then tighten down hard on the cover. Wipe with alcohol towel, then place in your fridge in a clean spot, that you have sanitized and cleaned with Electrasol or bleach solution. Some drawer or butter compartment or such is ok, and they should be kept very clean. In fact, you can place them inside a zip-lock bag for extra protection from the many contaminants inside the refrigerator. Refrigerators are notorious breeding grounds for all sorts of unwanted bacteria/fungi. They should be labled with a permanent marker as to date, type of yeast, common name, whatever you like. If you can obtain a separate small dorm-sized refrigerator from some student, this would be a better method of storage. Thoroughly clean the inside of the fridge with a sanitizing solution, and clean it on a regular basis to try keeping the contaminants down.

When using this method, a good supply of canned "starters" should be kept on hand for propagating the slants up to 1/2 or 1 gallon size. Get a good supply of canning jars, lids, and rings, and lots of shelf space. Get the jars super-clean as above, and place sterile wort right at end of boil into each jar, cap with lid and ring, and set aside to autoclave. I keep 1 quart and 1 pint jars on the shelf for propagating. These starters should be placed in pressure cooker, autoclaved at 15 psi for 30 minutes, then cooled and checked for good vacuum. Thoroughly wipe each jar when finished, and remove the rings, as if the lid pops off you know the jar was contaminated or lost it's seal somehow. I would suggest asking your wife or mother the proper method of "canning" wort, or you can locate a Ball Blue Book of Canning, which goes into great detail the proper steps to insuring a sterile long-lasting product. At this point, you will have your cultures in your fridge, and starters on the shelf.

A few days before brewing, remove a "slant" from the fridge, and let it come to room temp. Also, get a small jar of canned wort ready. Then, maintaining the super-sanitary procedures as above, transfer some of the aerated canned wort to the baby food jar and quickly re-cover. Lots of alcohol/flame can be used to insure no contamination. After a day or so, loosen the cover slightly to allow the gas to escape, as it is now fermenting rapidly. You can use an air-lock, but I use a piece of sanitized and flamed aluminum foil wrapped tightly around the neck of the jar. This allows the gas to escape, but keeps the nasties out, and there is less prospect of contamination than if an air-lock is used. You are on your own to figure a way to aerate the wort, I use an aquarium pump, peroxide/cotton filter, everything being super-clean and sanitized.

After you see a layer of paste forming in the jar, and the activity dies down slightly, you are ready to step up. I usually go to a 250ml flask, with aerated wort. Swirl the liquid in the baby food jar to get the paste in suspension, and pour the liquid into your next step up wort.

As a note on aerating the wort, I usually chill the wort in the refrigerator first. Then while very cold, pour the sterile wort into a sterile flask, with lots of head room to accomidate the many bubbles formed during aeration. Start your pump, and let her rip, and keep aerating while the wort comes up to room temp. Maintain extra-sanitary conditions all this time, as these are prime conditions for nasties sneaking in to your hard-prepared medium. Then, pour your smaller starter into the flask, cover with the sterile foil, and wait till activity starts slowing and you have a healthy layer of creamy white paste on the bottom.

Anywhere along this process, the best method I have found to test for contamination, is to both smell and taste the wort. Pour a small amount into a small sterile glass and sniff it, then taste. If the taste and smell is not "clean" and what you expect from that particular strain, throw the whole thing away and start from scratch. Also, especially before pitching the final 1/2 to 1 gallon starter in your wort, be sure to give it the smell/taste test. No sense wasting your 5/10/15/? gallons of wort to a bad starter.

This method of cultivation is not my idea, it was originally posted as a message in the FIDONET Zymurgy Echo, about 3 years ago, and I have since lost the original message when my hard drive crashed recently. This method of cultivation eliminates the need to re-use the paste from one batch to the next, with its inherent risks of cross-contamination. However, if you have the necessary equipment to wash your yeast at an accurate ph of 2.2 or so, then you can extend the yeast even further. So far, I have never had a contaminated batch using this method.

As to the longevity of these cultures, I would place 2 years as the useful upper limit. Simply take one of the cultures, place 30 ml sterile wort in the jar (using especially super-sanitary procedures), and make another batch from it after you get a healthy layer of paste. I recently started a London Ale slant from February 1994 (2 1/3 years), and although slow starting, it finally revived and made a great ale. I used this to re-inoculate my London Ale stock, so will be ready for another 2 years of brewing. This method of culturing seems to last as long as freezing, and is easier for me.

You are not limited to baby food jars. I happend on some 50 ml "oak ridge tubes" which work great, and one of our club members attended the closing auction at a local high school, and came home with loads of culture tubes, petri dishes, test tubes, stands, brushes, burners, etc. I rigged up one of the burners on my sink by tapping into the stove's natural gas line, so am now set up to flame the jar lids/rims in addition to the alcohol soak.

Our club, the Crescent City Homebrewers, is planning an informal "yeast ranch" for sharing and propagating cultures for the members. I hope you have as good luck as I have with your "ranching", and will find it a natural extension of the homebrewing hobby.

Culturing For the Rest of Us

If you'd sooner try something a little less complicated which still produces good results, try the procedure outlined below.

We used to use the process with a great deal of success until we switched to using mason jars and agar. We got this method from our friend Jean-Pierre Boileau in Montreal, Quebec, who's been using it for quite some time now with a great deal of success. It is based on the method outlined by Charlie Papazian in The New Complete Joy of Homebrewing, and is basically exactly like making a really small batch of beer except for a few minor things (that are very important) :

* don't require hops or grains (though regular beer wort can be used) * bottles must be stored in fridge afterwards * must be extremely anal about sanitation * you want the yeast sediment in your bottles

For a 1 pint starter bottle I just use a glass bottle from juice or something that is about 3 cups, and only fill it up 2/3. I bought a bung to fit it, and just use that. I have lots of different sized bottles and bungs that I've accumulated for doing starters and yeast propagation of various sizes.

If you only ever want to use 1 type of yeast, then it is even simpler because you don't have to bother with lots of different strains. Just boil up 500 grams (1lb) of dry malt extract in 4 litres (1 US gallon) of water. Dump it into a 1 gallon fermenter (that is extremely well sanitized), put on a fermentation lock (an S-type with little liquid so it won't suck back as the wort cools), and allow to cool to pitching temperature. At this point it is best to allow your break material to settle out, then carefully pour your wort off the sediment, leaving it behind. If you don't do this extra step, you'll be encouraging your yeast to spoil faster (although it will still last a long time). An alternative to making a special wort like this is to simply make up an extra amount of beer wort next time your brew. Best to use a lighter concoction, but dark is fine, too. Just draw off your gallon in a sanitary fashion, then use it instead of the specially prepared wort. Of course, this means that your yeast in question won't be able to be used for that brew.

Now, with your wort (minus trub sediment) in your 1 gallon fermenter, take your swollen Wyeast package and pitch it into the fermenter. Aerate the wort well either by shaking, or with an air pump. Let this ferment until it is done, then bottle it. However, before you bottle, you have to give the jug a really good shake to get all the sediment mixed into the beer again. This shaking has to be done extremely slowly and carefully so as to not cause a geiser. Little by little shake to release CO2. Eventually you'll be able to give it a good swirl to mix in all the sediment, without having it foam over. Afterall, the whole exercise is for propagating yeast, and most of that sediment is yeast. Note as well that you really have to soak your bottles well in your sanitziing solution, and make extra sure that all your equiptment is well sanitized. Also note that you can just pour the stuff from the gallon jug through a well- sanitized funnel into the bottles. I don't bother with a siphon as the yeast will gladly eat up any oxygen that gets in this way. Just be careful to clean the mouth of the jug well beforehand with some high-octane (80%) vodka or something, and possibly flame it with a lighter, too. This is the only time I actually bottle prime beer - I use about 3/4 tsp of corn sugar for each bottle.

Now that they are bottled, label them with the date and type of yeast and the GENERATION, and store them in the fridge. Note: they must be stored in fridge. Using a Bottle of Yeast

To use one of these for brewing, just take it out of the fridge and allow it to come to room temperature. Then open the bottle and carefully pour off about 2/3 of the liquid (you can drink it if you like, it's just beer). Now swirl the remaining liquid around to get all the sediment off the bottom, and pitch this into a 500ml (1 pint) starter wort (with airlock and so on). Keep swirling the starter every few hours, and when the airlock is bubbling every 10 seconds or less, then it is ready to pitch. After the first 2 or 3 batches you'll get to know how long it takes the starter to get going so you'll be able to time it better in the future. Each different type of yeast will be different, though.

We've got a page with in-depth details on using liquid yeast that will give you more information. TNG -- The Next Generation

When you are down to your last bottle, use it to make a new 1 gallon batch like above, but label these new ones as 2nd GENERATION. With this method, you should only go to 4 or 5 generations, then start again with a new Wyeast smack pack. But still, you'll be getting a good 30 to 50 batches out of that one pack, so you're still operating pretty cheaply.

-- ChristopherPepe - 12 Jan 2010