My friend Mark makes his own tempeh and recently documented his latest attempt for me so that I could blog about it. I'm including his instructions and the photos he kindly took to accompany them.
(makes about 2 lbs)
1 lb (2.5 cups) dried, cracked, dehulled soybeans
2 tsp tempeh starter
vinegar (lowers the pH, discouraging growth of competing bacteria)
Method 1 (my way): If you have a grain mill that can be adjusted to crack soybeans to dehull them, then this is the way to go. Once they are cracked (in around two pieces--not much more than that), take them outside on a dry and very windy day and pour the cracked beans back and forth between two large containers. The wind carries away most of the hulls leaving only the cracked soybeans for the next step. (I’ve seen suggestions to use a strong fan or hairdryer if the weather is not cooperating.) Soak these (at least overnight), covering them in water with a tablespoon of vinegar. Proceed to recipe.
Method 2: Buy the soybeans already cracked & dehulled. These are sometimes called ‘full-fat soy grits’. Soak these (at least overnight) covered in water with a tablespoon of vinegar. Proceed to recipe.
Method 3: Cover whole soybeans with boiling water with 1 Tbs of vinegar, and let soak at room temperature at least overnight. Next, pour off the water and rub the beans in the pot vigorously between your hands to slide off the hulls and split the beans into halves manually. Fill the pot with water and stir to allow the hulls to rise to the surface. Skim off the hulls and repeat the process till most of the hulls are gone. (Ugh!) Proceed to recipe
1) Rinse the soaked soybeans, place in large pot with 10 cups of water and 1-1/2 Tbs vinegar. Bring to a rolling boil and cook, uncovered, for 30-45 minutes. Keep an eye on them, as hulls and foam will rise to the surface in the beginning and can overflow. Skim off the hulls/foam as they rise to the top (it gets less touchy after the first 15 minutes or so).
2) Drain beans into colander and then transfer into large clean bowl. Let beans cool uniformly by pressing the beans into the concave shape of the bowl till about room temperature.
3) Sprinkle 1-1/2 Tbs of vinegar and mix thoroughly using a clean wire whisk. Now sprinkle 1 tsp of tempeh starter over the beans and whisk in thoroughly. Add the other 1 tsp of tempeh starter and mix thoroughly again.
4) Press inoculated beans into clean containers or Ziploc bags. Avoid touching the beans with your hands (even though you washed them very well, with soap, before you started all this, right?). Beans can be anywhere from 1/2" to 1-1/2” thick. If pressed into a container for incubation, cover lightly with plastic wrap so top does not dry out before it gets a chance to colonize.
Note: I have made myself plastic tempeh moulds out of old margarine containers. Any clear plastic containers would do (so you can see the progress). Drill small (around 1/8”) holes spaced about an inch apart and in a grid pattern into the container. Perforated Ziploc bags can be used too.
5) Tempeh needs an ideal temperature of 86-88 F. (30-31 C) to incubate. Slightly cooler (down to 80 F / 27 C) will still work, though much slower increasing chance for contamination, and too hot can kill/end the process. The easiest method without building/buying some contraption is to use the oven with just the light on inside, but you have to use an accurate thermometer to figure out how to have the oven temp ‘hover’ around that ideal temperature range. An outdoor thermometer will work fine. Variables include room temperature, which rack inside the oven you're using, how close to the bulb your have your stuff, whether the oven door is closed or propped open more (or less). Do all of this temperature experimenting BEFORE your first batch goes in and you should succeed the very first time!
Incubation takes about 20-24 hours at the proper temp. About 2/3 of the way through, the tempeh starts generating it’s own heat (a lot of it--you can really feel it). At about this time you should a) move the tempeh to a lower rack, or b) prop the oven door open a bit more wider, or c) turn off the oven light altogether to avoid overheating. Sometimes you’ll see the corner of the tempeh closest to the heat source seem more advanced; rotate the tray so that the other side can ‘catch up’.
6) When the tempeh looks all white and firm (pretty much like the store-bought stuff) you can cut it up and use it, refrigerate it, or freeze it. If you let it continue to grow it will begin to produce surface spores (grey to black). This is no problem and is still edible. Ammonia overtones will increase and tempeh will get stronger if allowed to over-ripen and is still safe, within reason (some people even prefer it this way). If it starts smelling foul or turning odd colours or textures, maybe you’ve gone too far and it’s time to toss it and make a new batch.
Note: If unavailable at your local health food store, you can order tempeh starter online from a place like GEM Cultures.