How to make your own tempeh at home
I got my tempeh starter from Cultures of Health and one packet is good for 2 cups of soy beans and so that's the amount I used.
Place 2 cups of soy beans in a large pot. Pour cold water and bring the water to just boil and then turn off the heat and cover. Let it sit for at least 6 hours or up to 24 hours
Drain off the water and fill with more fresh water and use your two hands to rub the beans as if you are washing your hands. This will rub off the skin off the soy beans. The skin will rise to the top of the water and scoop those skins away and pour off the water and fill up with fresh water and rub again. Do this for about 8-10 times, or until you take off most of the skin. You may not be able to take off all the skin, but take off as much as you can, but there's no need to be obsessed about it. This is important because if the beans are still with the skin intact, it won't culture properly. Place the beans back to the pot and fill up with water, bring to a boil and then lower the heat and cover the pot and cook for 1 hour. Just check on the water to make sure it doesn't run out while you are boiling it. Strain off the water after 1 hour
While the beans are boiling, you can prepare three to four 1/2 quart-size ziplock bag that are already poked with needle on both sides (1-inch apart). I don't recommend using too big of a bag (which was what I did when I failed the first time) as it won't culture properly
Spread two to three dry clean absorbent cloth on the kitchen counter or wherever with enough space. Spread the cooked beans on the cloth and use the towel to gently rub the beans to dry it. The beans will slowly cool down, but don't let them turn cold. It should be about body temperature or slightly warmer.
Place the dried but still slightly warmed bean in a large bowl. Pour in 2 Tbsp of distilled white vinegar and sprinkle 1 packet (about 1 tsp) of the tempeh starter. Use your clean hand to mix it thoroughly, to make sure the beans are covered with the starter and vinegar. Fill the bags with the beans, making sure you fill it to the corner but do not over pack it. It shouldn't be more than 3/4-inch in thickness. Seal it. Place them on top of wire rack and place it in a warm place (about 85-90 Fahrenheit). When I made this, it's still winter, so I place this inside whole set-up inside the oven and warm the temperature to around 90 degrees and turn it off. Place a thermometer inside the oven so you know the temperature
How do I maintain the warmth ? I turn on the light inside the oven (figured that out by accident) and it magically help me maintained the temperature inside the oven around 90.
Nothing will happen for the first 24 hours in my case. Some shows result starting at 20 hours. Mine started to grow rapidly after 30 hours. The tempeh is done when it covers with white spores all over and you can pick it up like a block without it breaking apart. It should be firm. Freeze it if you are not going to cook it in a week time. It's good up to 6 months in the freezer and about 1 week in the refrigerator.
If during the process, the spores turn black and the tempeh is soft, you need to discard it. Those have some toxins.