Making Betsy’s Tempeh for a large family or a group :
Get a “5 day or 6 day” cooler that is big enough for a standard food industry pan, which is slightly larger than 20”x12”. (Look on the web under restaurant supplies: 1/1 steam table pan).
We used the full size ( high temperature) poly carbonate pan with a depth of 2.5”. These pans also come in stainless steel and are available with lids. Lids are useful when adding marinade to the finished tempeh (low salt tamari for example) and putting the tray into the refrigerator overnight. Lids are also good for pasteurizing the tempeh after incubation.
The cooler needs to be a few inches longer and wider than these trays. Make sure you double check your measurements before you buy your cooler. The cooler we tested is the Igloo 100 qt 5 day cooler (with wheels).
There are two methods of operation: Occasional Use and Daily Use.
Occasional use: If you want to make tempeh for your family or group once or twice a week, just roll the cooler to where your water is available. When finished, roll the cooler to a drain or use the water for your garden, then let the incubator dry out until the next time you want to make more. In the 100 qt Igloo with a full size pan you need at least 8 gallons of water, that makes the water level only about 4.5” deep. The aquarium heater we used has a digital readout and is easily adjustable from the outside. We also recommend working with a Ground Fault Circuit Interrupter.
For daily use you might want to use a small aquarium pump to circulate the water through a UV Sterilizer (see our Notes). That way you can operate the incubator for quite a while without having to drain the water each time. You will still want to occasionally empty the water and clean the cooler with a sponge soaked in vinegar. At this point nobody knows how long a cooler will stay clean - please let us know your results. What we do know is that it is very important to keep the underside of your pan clean before putting it into the cooler to incubate.
How much water to use? Because tempeh starts generating heat half way through the incubation period, a certain amount of water is used to keep it from getting too hot. The little red cooler ( in the DVD) had about 5 gallons and at the end brought the temperature up to 93∘ F (in an 85∘ F climate). In a cooler climate the temperature might not rise very much.
By using more water or less water you can fine tune the end temperature; we would not recommend letting it get above 93∘ F. With more water you can pretty much hold the temperature level at 89 - 90∘ F.