Abstract
To elucidate the mechanism of softening of Combu fronds by seasonings during the cooking process, calcium release from calcium alginate (Ca-Alg) immersed in a solution of sodium salt of organic acid was examined. Regardless of concentration of seasonings, calcium release from Ca-Alg reached equilibrium following immersion for a few minutes. The effect of immersion temperature on the rate of calcium release was not so significant. The lower the degree of polymerization of Ca-Alg, the greater the degree of calcium release, but differences were not so significant. Sodium salts from organic acids were classified into four groups according to the degree of calcium release. The most effective group consisted of disodium hydrogen citrate and sodium citrate, followed by sodium malate and sodium tartarate and finally by sodium lactate, sodium succinate, sodium hydrogen tartarate and sodium dihydrogen citrate. The least effective group consisted of sodium acetate. Ion exchange selectivity coefficient for exchanging Ca2+ for Na+ was significantly larger in the case of sodiumcitrate, sodium hydrogen citrate, sodium malate and sodium tartarate. These results revealed the type of seasonings and the concentration which were most effective for release of calcium from Ca-Alg.
