Keiko Kumeno

Freeze concentration of some foodstuffs using ice nucleation-active bacterial cells entrapped in calcium alginate gel

Cells of an ice nucleation-active strain of Ermnia ananas were entrapped in calcium alginate to prepare an ice-nucleating gel usable as ice nuclei for freeze concentration. The ice-nucleating gel was also adjusted as to specific gravity. When it was placed at a desired position in a liquid material such as egg white, ice formed at this position as the material was cooled. It was possible to put the ice- nucleating gel in liquid foodstuffs such as egg white and lemon juice before their temperatures reached subzero points. Application of this method produced freeze-concentrated foods whose properties were not significantly deteriorated.

High-pressure Sterilization of Ice Nucleation-active Xanthomonas campestris and Its Application to Egg Processing

Xanthomonas campestris INXC-1 is able to freeze water at a subzero temperature higher than -5°C. High-pressure treatment at 300 MPa and 5°C for 5 min killed the cells without affecting their ice-nucleation activity. Egg white containing the pressurized cells began to freeze with a slight degree of supercooling. Ice crystals with a dendritic structure were formed when the egg white froze in the presence of the killed bacterial cells. The frozen egg white thawed more quickly than egg white frozen without the cells.