Abstract
To determine the effects of high pressure and sucrose on improving the quality of frozen-thawed gel, kappa and iota carrageenan gels with 0, 5, 10 or 20% sucrose were frozen at 0.1~686 MP and −20°C. When pressurized at 200~400 MPa, they did not freeze. However, when pressure was released, the gels froze quickly by pressure-shift-freezing. Consequently, ice crystals and syneresis of pressure-shift-frozen κ-carrageenan gel were smaller than gels frozen at other pressures, although rupture stress decreased. Thus, pressure-shift-freezing was effective in improving the quality of frozen-thawed κ-carrageenan gels. Conversely, the trace of ice crystal was not observed in all frozen-thawed ι-carrageenan gels, syneresis was slight, and the quality of gels was the same as non-frozen gel. Thus, freezing tolerance of ι-carrageenan gels was greater than κ-carrageenan gels. The addition of sucrose to both kinds of gels was effective in improving the quality of frozen-thawed gels.
