Fermentation - Tempeh

Introduction

Originating on the island of Java, in present-day Indonesia, tempeh is quickly gaining in popularity in North America as a versatile and delicious meat substitute.  Traditionally, it is made from soybeans, but the same culture and fermentation process can be used with other legumes.  The result is a hearty patty with a mild flavor of mushrooms that's low in fat and packed with nutrition.

The Basics: Boiled and cracked soybeans are inoculated with a culture of tempeh spores and incubated for at least 24 hours, during which time a web of white mycellium envelopes the beans and binds them together.

Quick Reference
Materials
  • Hulled soybeans (If you can't find pre-hulled soybeans for purchase, you can remove the hulls yourself with one of the methods described here.)
  • Tempeh Culture
  • Vinegar
  • Strainer
  • Clean towel(s)
  • Large bowl
  • Ziploc bags or baking pan and aluminum foil
  • Thermometer
Instructions
  1. Boil beans for approximately 1 hour, long enough to soften them, but not to the point you'd want to eat them.  They will continue to soften as they ferment.  Skim off any foam and remaining hulls that float to the surface.
  2. Strain beans and spread them on a clean towel.  Use the towel to pat the beans dry.  Depending on the size of your towel, you may want to do this in several small batches or use more than one towel.  You want the beans to feel dry to the touch; too much moisture can ruin the batch.
  3. When beans are thoroughly dried and cooled to body temperature, place them in a bowl and mix in vinegar.  The acidity of the vinegar keeps potential contaminants at bay until the tempeh spores take over.
  4. Sprinkle tempeh spores over the beans and mix well to evenly distribute them throughout the bowl.
  5. Spoon the bean mixture into Ziploc bags and pierce the bags all over with needle-sized holes for ventilation.  The bags should be 1" to 1.5" thick with beans.  Alternatively, spread the mixture about 3/4" thick on a baking tray and cover with aluminum foil pierced all over with ventilation holes.
  6. Now the tricky part: incubation!  Whereas a fluctuating room temperature will suffice for most ferments, tempeh needs to incubate at 85 to 90 deg. F (29 to 32 deg. C) for 24 to 48 hours.  Some ideas for incubator set-ups: an oven with the pilot light on, a food dehydrator on low setting, a cooler with hot water bottles or a heating pad.  Read more here
  7. After 12 hours, check the tempeh.  Around this time, it will start to generate some heat of its own; you may have to adjust your heat source or remove it completely if the tempeh is getting too warm.  
  8. Continue to monitor the tempeh, checking that the temperature stays in the right range.  During the second half of the fermentation period, you will see white mycellium threads starting to spread throughout the beans
  9. When the mycellium has formed a dense mat that holds the beans together, the tempeh is ready to be refrigerated.  
  10. Remove tempeh from your incubator and allow it to cool to room temperature before refrigerating.  
Frequently Asked Questions

Should I be worried about grey or black spots on my tempeh?

Grey and/or black coloration usually appears around the ventilation holes because it is the result of oxidation.  It is totally normal and safe to consume; in fact, store-bought tempeh usually has grey patches and commercial labeling specifically states that the coloration is a part of the process.  Take it as an indication that the tempeh is done.

What can I use besides soybeans to make tempeh?

The recipe above is for a very basic tempeh, which is traditionally made from soybeans.  However, the same culture and process can be used with fava beans, chickpeas, black-eyed peas... you name it!  You can even make bean-less tempeh with nuts and/or cooked grains like oats, rice, or millet.  

What exactly is a tempeh starter culture?

Powdered tempeh starter culture is a mixture of Rhizopus Oligosporus mold spores and a starchy substrate such as rice flour.  The substrate helps even out the application of the spores to a bean/grain mixture.

Additional Resources

http://www.motherearthnews.com/real-food/how-to-make-and-cook-tempeh-zmaz77sozgoe.aspx?PageId=1.  Detailed article about making tempeh, including extensive how-to and what-if discussion as well as linke to recipes.  Originally appeared in Mother Earth News in 1977.

http://www.npr.org/sections/thesalt/2013/04/05/174847636/journey-to-javas-tempeh-village-where-soybean-cakes-are-born.  A NPR story with pictures showing tempeh-making in an Indonesian Cooperative: not really a how-to article, but wonderful story highlighting the cultural practice and context of tempeh-making.

Katz, Sandor Ellix.  Wild Fermentation.  (2003)  A collection of recipes for a wide variety of fermented foods from around the world, including tempeh and much more.  More then just a culinary reference, this book is sprinkled throughout with anecdotes that make it worth a cover-to-cover read.


Tempeh Supplies