Stringent microbiological standards and surveillance programs should be established to prevent illness from tofu, point out Southern Illinois University (SIU) researchers. A voluntary standard developed by the Soyfoods Association of North America (SANA) is the only guideline currently in place.

The high protein and moisture content of tofu make it a favorable medium for microorganism growth, say researchers. And, since it's also precooked, it may be eaten without further cooking.

In food-safety terms, tofu is classified as a potentially hazardous ready-to-eat food.

Six brands of tofu in an SIU research project were purchased from eight stores and analyzed for temperature, pH, total aerobic bacteria and the presence of coliforms. Relationships between remaining shelf life, temperature, pH of tofu and total aerobic bacteria were tested.

Of the tofu samples tested:

* 55% fell within the SANA excellent range for freshness.

* 6.7% were within the acceptable range.

* 6.7% fell within the marginal range.

* 28% were in the unacceptable range.

The majority of the tofu was displayed at unsafe temperatures for potentially hazardous foods, say the Illinois scientists. Sixteen percent of the samples contained coliform bacteria. High numbers of E. coli were detected in bulk tofu and were associated with a lower pH.

The U.S. has little culinary tradition with tofu, and many consumers are unable to judge its spoilage. Outdated tofu and displays of gassy packages indicated the food handlers' and consumers' lack of knowledge about the nature of tofu. Thus, there is a need to educate store employees and consumers about its perishability, say the researchers.

(Hea-Ran Ashraf, Mary White and Brian Klubek, Southern Illinois University)