Only three soybean product factories in Taiwan use a sterilized vacuum packaging process, the Department of Health said Friday after dried tofu in vacuum-sealed plastic sacks was suspected in a series of botulinum poisoning cases. Citing a survey conducted by the Hsinchu-based Food Industry Research and Development Institute, the department said the three factories are D. E. Chung Hua Foods Co. Ltd. in Gangshan, Kaohsiung County; Fu Che Frozen Food Co. in Lujhu, Kaohsiung County; and Dafang Foods Co. in Dasi Township, Taoyuan County. Only tofu products that are thoroughly sterilized before being vacuum-packed should be stored or displayed in room temperature environments, it said. Products from factories that do not properly sterilize their dried tofu should be refrigerated until eating, health officials said. Although there is no law to forbid factories that do not sterilize their dried tofu from selling their products in vacuum-packed bags, health officials said it could make consumers wrongly think the products are safe for room-temperature storage. The department revealed the results of the survey one day after two new cases of botulinum poisoning were confirmed. Tsai Shu-chen, a Department of Health official, said one of the cases involved a 36-year old teacher from Yunlin who fell ill June 8, one day after eating vacuum-packed dried tofu from a Dasi factory. He was admitted to a hospital and discharged June 30 after recovery. Another case involved a 72-old woman from Kaohsiung who fell ill June 25, one day after eating vacuum-packed dried tofu also produced in Dasi. She remains hospitalized. As an anaerobe, botulinum does not require oxygen to grow and thrives in vacuum sacks if not sterilized thoroughly, posing a serious risk to consumers, a health official said. The Department of Health said it is working on guidelines for the manufacturing of vacuum-packed foods and could publish it as early as next week to seek public opinion. The guidelines could become regulations within three months of publication. Taiwan has seen eight botulinum poisoning cases involving 11 people since April. One person was killed, five remain hospitalized and five others have been discharged from hospitals after treatment. 