Abstract
Steamed and dried sweet potato is one of the Japanese traditional foods. Since the import of sweet potato products is increasing recently, the quality improvement of steamed and dried sweet potato is required. In recent years, the phenomenon that the central part of the steamed sweet potato becomes white in the manufacturing process of steamed and dried sweet potato came to be seen. In order to solve this problem, two experiments were carried out in the real manufacturing process of steamed and dried sweet potato. When the steam pressure of boiler was raised to 1.1kgf/cm2 from a general level of 0.8kg/cm2, the white spots of steamed sweet potato disappeared within a shorter time. Moreover, under the pressure of general level of 0.8kgf/cm2, by letting sweet potatoes pass through hot water of an iron pot, generating of white spots were able to be prevented and steaming time was apparently shortened. Furthermore, by raising slowly steaming temperature and heating it enough, hydrolysis of sweet potato starch was promoted and retrogradation of the starch was prevented. Based on these numerical analyses, the control technology of steaming which could manufacture the sweet and soft product of excellent in quality was developed. It depended for the manufacturing process of steamed and dried sweet potato on the traditional experiences until now. These results were able to show technologies numerically and it was able to use for preventing of white spots generation. Based on these research results, the processing technology of high value-added of steamed and dried sweet potato was developed.
