Simple freezing and thawing protocol for long-term storage of harvested fresh Undaria pinnatifida

The development of a simple and effective long-term storage protocol for harvested fresh Undaria pinnatifida is required to increase the market for U. pinnatifida products. We investigated the quality of U. pinnatifida after the application of various freezing and thawing methods to establish an optimum storage protocol. Four freezing temperatures (−40, −30, −20, and −10 °C), four freezing conditions (in air without seawater and with 50, 75, and 100 % seawater), and four thawing times (6, 12, 18, and 24 h) were employed. Changes in color value, tensile strength, total bacterial count, and most probable number of coliforms were measured. The best method for preserving the overall quality of U. pinnatifida is freezing at −30 °C with 50 % seawater and thawing in running tap water for 6 h. During retail display, changes in color, odor, tensile strength, and bacterial count of U. pinnatifida that had been freeze-thawed under optimum conditions were also measured, and a sensory evaluation was performed. There was no significant difference compared with the control within two days at 10 °C. In conclusion, we developed a simple and effective long-term storage protocol that led to no significant loss of quality of fresh U. pinnatifida .