1984 Volume 31 Issue 2 Pages 92-103
The thermal processing for soymilk, which was capable to inactivate spore-forming microbes and to ensure the favorable consistency, was tested in order to facilitate the manufacture of Tofu products with satisfactory keeping quality. HGU method, an advanced thermal process for soymilk by means of UHT process with preceding germination subsequent to heat activation, was developed in the present study. The results obtained were summarized as follows; (1) Stimulation of germination of externally-added Bacillus subtilis ATCC 6633, to a rate of 74%, was achieved by heat activation of soymilk at 80°C for 10min while the rate of germination without the heat activation was 63%. Subsequent germination process at 37°C for 30min led to a higher germination rate up to 86%. (2) In order to inactivate spore-forming microbes in soymilk which were migrated from the soybean or externally contaminated during soymilk production, the heat activation and the germination processes were prerequisite and the practice of these two processes in sequence was observed to be more effective for the production of Tofu having satisfactory keeping quality. (3) The period for keeping quality was significantly prolonged by holding the soymilk, prepared by subjecting to heat treatment at 100°C for 4min, at 5 to 15°C for 17h prior to heat activation process as compared with the case of immediate heat activation of the soymilk omitting an intermediary cooling process described above. (4) The effect of the practice of the sequential heat activation and the germination processes upon the germination of spore-forming microbes, was more convincing when the subsequent UHT process was conducted at 125°C as compared with the case of UHT process at 130°C. (5) The soymilk, prepared by the HGU-method, ensured a more favorable flavor persistence in resulted Tofu than in those which were prepared by the traditional method. Tofu prepared by the former procedure was equivalent to those prepared by the latter one with respect to physicochemical properties such as color, and consistency, in addition to the improved keeping quality.
