Abstract
One of our authors has found that the dip for buckwheat noodles, a mixture of a cold-water-extract of Katsuobushi and soy sauce at a ratio of 3 : 1, became tasty and soft after aging at low temperature.
This aging effect was proved by sensory tests of a dip before and after aging. The content of formol-N and 5'-IMP in the dip increased slightly and minimally respectively, during aging. The increase of “Umami” taste after aging could be seen neither when the boiling-water-extract was used nor when the cold-water-extract was steamed.
When the 5'-AMP was added to the dialyzed solution of the cold-water-extract and incubated, 5'-AMP decreased markedly corresponding with increase of 5'-IMP. Decrease of 5'-AMP and increase of 5'-IMP was more drastic in the cold-water-extract from the surface layer of the Katsuobushi.
These results suggest the existence of an enzyme in the cold-water-extract of Katsuobushi. This enzyme is assumed to be derived from the surface layer of Katsuobushi, where mold had been inoculated, and to transfer 5'-AMP to 5'-IMP.
We conclude that the “Umami” taste of the dip made from the cold-water-extract was enhanced by the synergistic effect of the components, that is 5'-IMP, free-amino-acids, and peptide during aging, however each component individually showed slight increase.
