Table of Contents
Pfaff, G. and B. Shipley. 1996. New technology for
making tempeh: A cultured soyfood. p. 509-211. In: J. Janick (ed.), Progress
in new crops. ASHS Press, Arlington, VA.
New Technology for Making Tempeh: A Cultured Soyfood
Gunter Pfaff and Betsy Shipley
- FUTURE PROJECTS
- Fig. 1
- Fig. 2
- Fig. 3
Tempeh, a soyfood which originated in Indonesia several hundred years ago, is a
valuable source of plant protein. Partially cooked dehulled soybeans are
inoculated with the fungus Rhizopus oligosporus and left to incubate for
about 22 h at 30°C. The white mycelium which develops ties the soybeans
together and improves the nutritional profile, resulting in a semi-firm cake
which can be served in a large variety of dishes.
When tempeh began to be produced in commercial quantities in the United States,
the most prevalent production method was that developed by Martinelli and
Hesseltine (1964). The partially cooked, inoculated soybeans were incubated in
a perforated plastic bag and frozen after incubation was completed.
There are however numerous advantages to incubating tempeh on trays rather than
in plastic bags. The finished tempeh can be pasteurized, cut into various
shapes, and premarinated with different flavors before being frozen. In this
paper we describe a new method for producing tempeh on trays.
The first book on tempeh production (Shurtleff and Aoyagi 1980) reported
problems utilizing stainless steel trays for tempeh incubation because the heat
generated in the heat producing phase of incubation was insufficiently
dissipated. The original experiments by Martinelli and Hesseltine were even
more negative: "Metal trays without perforations, no matter what kind of
covering was used, did not produce a good tempeh, since aeration of the whole
mass of soybeans was insufficient for mold development." We first overcame
this problem by incubating on a specially designed rack which circulated air
under the trays. However this necessitated multiple handling in order to end
up with a pasteurized product. We concluded therefore that it was necessary to
abandon the traditional incubation room concept.
Tests had shown that circulating water was excellent for heat dissipation. A
waterbath incubator would allow pasteurization at the end of the incubation
period by raising the waterbath temperature to 80°C for 15 min (Fig. 1).
The substrate is on a stainless steel tray. This tray sits on a support and is
partially submerged in the waterbath. An insulated lid covers this tray and
seals it from the environment. Air is injected under the lid and drifts over
the incubating tempeh to exit at the opposite end. The temperature of the
circulating waterbath is closely regulated for both heating and cooling.
The utilization of stainless steel trays for this process was important since
food-approved stainless steel is the standard in the commercial food business.
Aluminum trays were not considered since the relation of aluminum to
Alzheimer's disease is not clear at this time. Other metal trays are available
which have a food-approved coating, but this would not stand up to daily use.
Fiberglass trays with a food-approved coating would not hold up to the high
temperatures reached during pasteurization.
We subsequently constructed an incubator/pasteurizer with 14 large stainless
steel trays which has now been operating flawlessly for three years (Fig. 2).
This apparatus and method has been patented (Pfaff 1993, 1994).
Our 14 tray unit has consistently produced high quality tempeh without
overheating or producing premature sporulation (Fig. 3).
A production incubator/pasteurizer for a larger facility might consist of two
waterbath units (one above the other) using a total of 28 trays and producing
70 kg of tempeh every 24 h. Because stainless steel trays are used, the
product can easily be premarinated with different flavors before being packaged
and frozen. For example, premarinating with a low salt tamari--a wheat free
soy sauce--is suggested as an additional product line.
During our market testing in the regional market, we have sold the product as
unflavored patties and in grated form. We have produced this tempeh on a part
time basis and marketed about 3200 kg/yr. Acceptance by health conscious
individuals and chefs indicate this product has a very promising future as a
healthy alternative food.
The tempeh we produce (made with organically grown Vinton soybeans and some
barley) has an excellent nutritional profile but has 26% calories from fat.
This might be improved by creating a low fat soybean. Modification of the
Rhizopus oligosporus culture (which produces a pure white mycelium) is
suggested. Tempeh with a light brown mycelium would be more acceptable to the
public since it would look more like the customary meat protein.
- Martinelli, A.F. and C.W. Hesseltine. 1964. Tempeh fermentation: Package and
tray fermentations; Food Technol. 18(5):167-171.
- Pfaff, G. 1993 and 1994. Apparatus and method for culturing plant materials as
foods. U.S Patents 5,228,396 and 5,312,630.
- Shurtleff W. and A. Aoyagi. 1980. Tempeh production; The book of tempeh, Vol.
II. Center, PO Box 234, Lafayette CA.
Fig. 1. Simplified diagram of waterbath incubator.
Fig. 2. A 14 tray waterbath incubator/pasteurizer for tempeh production; lid raised, trays filled with substrate; each tray will produce approx. 2 kg of tempeh every 22 h.
||Fig. 3. (Left) Incubated and pasteurized tempeh cake from one tray cut into 26 patties; the four corners will be made into grated tempeh.
||(Right) The mycelium is fully developed throughout the tempeh because of unrestricted aeration and accurate temperature regulation.
Last update August 24, 1997