Relationship between the Turbidity of Dashi (Soup Stock) Made from Fushi (Boiled, Smoke-dried Fish Fillet) and the Chemical Components Present, and the Component Mainly Responsible for the Turbidity

摘要

Turbidity in dashi (soup-stock) made from some different kinds of the fushi (boiled, smoke-dried fish fillet) poses serious problems for the fushi shavings industry, because turbidity in dashi reduces the commercial value of the shavings of fushi to make clear soup, which is essential in Japanese dishes that usually required transparency. This study aimed to elucidate the relationship between the dashi turbidity and the chemical components of the dashi and the fushi. We also sought to determine the component mainly responsible for the turbidity. It was clear that the more crude fat the fushi contained, the more turbid the dashi became. The correlation coefficients (r = 0.886) between the turbidity and the crude fat content of dashi indicated that the lipid were the main causative component of the turbidity. Observing the shaving with scattering electron microscopy, lipids of the fushi were found as granular fat globules between the dried muscular fibers in the fushi. These globules dispersed into the dashi during extraction. We also determined that the main lipid component in the dashi turbidity were triglycerides and phospholipids.