For the purposes of speedup, rationalization and commercialization of extraction methods of kombu soup stock, we studied on a heating extraction method in which ultrasonication was used jointly in the heating process as a new processing method of food. Moreover, the relationship between the extractable components of kombu soup stock and the tastes and the optimum preparation conditions were examined.
1) Slightly larger amounts of the constituents were extracted from kombu and a better soup stock were produced by using the heating method introducing a step of applying ultrasonication than in the control without ultrasonication.
2) Soup stock was obtained in a shorter time. Under the most appropriate condition for preparation of kombu soup stock, the optimum heating times were 8 minutes for the ultrasonication method and 15 minutes for the method without ultrasonication.
There were no significant differences in the soup color between the two methods.
The contents of total extracted components, total nitrogen,5'-nucleotides and minerals in the soup were nearly the same for the two methods, whereas the contents of free amino acids were higher in the soup obtained by 8 minutes ultrasonication, producing a more satisfactory soup, and leading to decrease in the consumption of electric power, compared with the control without ultrasonication.
Therefore, the cooking method involving a step of ultrasonication is considered useful when the soup-stock is used together with the traditional heat applying method or the water extracting method.
