October 7, 2000: Charlotte, NC-- Last time we talked about the preparations for slants. Well now we're going to inoculate those slants. The procedure depends on what the source is for your yeast to be cultured. For simplicity, we'll describe the culturing process from a packet of Wyeast.

Before we start, section off a clean and well lite work area where you can organize all your items. The key is to minimize the amount of movements and ups & downs, throughout the procedure. This will enable you to move quickly and efficiently and reduce the risk of possible contamination (remember: yeast culturing is extremely susceptible to infection).

Next, make sure you can proceed without any distractions (e.i. take the phone off the hook, send the kids out to play). Then wash your hands thoroughly and begin. It may not be a bad idea to quickly rinse your hands with a bit of ethyl alcohol before you dive in.

Presumably your Wyeast pack has been smacked a day or two earlier and it's ready to go. Have your Wyeast pack, slant vials, an unwrapped paper clip, long needle or inoculation loop, a cotton ball or folded up paper-towel, your vial of ethyl alcohol, and your starter vessel laid out on clean paper toweling, along with an empty, unused slant vial that has been sterilized, along with its cap.

1. Have your starter wort ready and waiting for the Wyeast contents.

2. Take a deep breath and hold it. Shake the Wyeast pack well, and then open it using a pair of sterilized scissors. Pour a small bit of the Wyeast solution into your empty vial, and pour the rest into your starter. Cap your vial, and attach your airlock to your starter. Resume breathing. Your starter will be ready to use within t a day or two; the small quantity of solution will be used to inoculate slants.

3. Now repeat the following sequence of actions for each slant vial you wish to inoculate. These steps should take under 15 secs:

a) Take a deep breath and hold it. Wipe your needle/paperclip/innoculation loop with alcohol-moistened cotton/paper towel to sterilize it. If you wish, you may also use a flame source for sterilizing: simply heat the end of the inoculation device in the flame till red hot and then cool on the inside edge of the vial. b) Open the slant vial to be inoculated. c) Then open the vial with the bit of Wyeast solution in it. d) Dip your needle into the Wyeast, and then lightly poke it into the surface of the gelatin + malt growth medium in the slant vial. Poke it in a bunch of places. Smear it around. However, try not to touch the walls of the vial. e) Withdraw the needle, cap the slant vial, and cap the Wyeast vial. f) Resume breathing

You now have a fully inoculated slant vial. Keep doing this for as many vials as you wish to inoculate.

4. When done, leave the vials out at room temperature (20 deg C) for a week. Within a couple of days you will see a cloudy film on the slant surface, and a few days later it will develop into a milky white layer about a mm thick. Sometimes, depending on the strain of yeast involved, the ambient temperature, and the richness of your growth medium, the CO2 evolved from the yeast growing on the slant surface may begin to push the cap up off the vial. No big deal-- just bleed the gas out by cracking open the cap for a moment, and press the cap back down firmly. After the week is over, wrap the tops of the vials (where the caps meet the vial walls) with electrician's tape, and put the vials into a ziplock bag and pop them in the fridge, where they will keep for at least 3 months in a perfectly viable condition. Obviously, if you are keeping more than one yeast type around, you will want to label the vials somehow--masking tape works perfectly for this.

Next time, we'll look at culturing from a bottle!!

Yeast Culturing Kit Components

Starter tube: A small, capped tube containing 10-15 mL of sterile wort. Used for expanding culture size. Flask: A laboratory-grade (Erlenmeyer) flask, narrow at the mouth but wide at the bottom, usually 1/2 or 1 L in size. Used for expanding culture size. Slant: A small, capped tube containing solidified (gelled) sterile wort. Used for long-term storage of yeast samples. Yeast is often supplied on slants when purchased. Plate: A short, wide, covered dish to be half filled with solidified wort. Often called a petri dish. Used for isolating yeast colonies and short-term storage. Inoculation loop: A metal rod with a wire extending axially from one end. The end of the wire forms a small loop. Used for transferring small amounts of yeast. Growth media: Dry malt extract plus nutrients to feed growing yeast. Many specialized media are available, but this combination is easy for craft brewers to obtain, store, and use.

Click here to read Yeast Culturing Part I


References:
CULTURING YEAST AND USING SLANTS
by Dave Draper, Sydney, Australia, January 1995