Buffering Capacity of Dried Skipjack (Katsuobushi) and the Other Fish Stock (Dashi) Materials and the Compounds Contributed to Them

Abstract

Measurement of buffering capacity (BC) has been tried to apply for checking the qualities of various foods. The compounds contributing to the BC, however, has been scarcely identified hitherto. We determined the BC of dried skipjack (Katsuobushi) and the other fish stock (Dashi) materials in the neutral pH range of 6.0-8.0, and identified the compounds contributing to the BC. Among eight Dashi materials, Katsuobushi showed the highest BC in the pH range 6.0-7.0, followed by dried frigate mackerel, dried sardine, and dried mackerel. Contribution of histidine-related compounds such as free histidine, carnosine, and anserine was as high as 40% to the BC of hot-water extracts from Katsuobushi, while the contribution was almost 20% in the case of dried mackerel and dried sardine. Inorganic phosphate contributed above 80% to the BC of hot-water extracts from dried mackerel and dried sardine, while below 40% in Katsuobushi. Histidine-related compounds and inorganic phosphate accounted for above 80% in total to the BC of the above dried fishes. In umami stock which contained large amounts of nucleotides and glutamic acid, on the other hand, these compounds were responsible for the greater part of the BC.