Abstract:Physicochemical study, texture analysis and low-field 1H NMR method were applied to analysis the changes of water holding capacity, texture property and water mobility of Pseudosciaena crocea frozen by different methods，including slow freezing (SF), quick freezing by immersing in ultra-low temperature ethanol (QF-UTE) and in liquid nitrogen (QF-LN). The results showed that the quick frozen samples revealed a relatively lower freezing loss and thawing loss, otherwise a relative higher juice loss and cooking loss, compared to the SF treated samples. Quick frozen samples also showed higher texture properties in hardness, adhesiveness, chewiness and resilience, while the adhesiveness, springiness and cohesiveness of SF samples were relatively closer to those of unfrozen fish. The transverse relaxation time of Low-field 1H NMR indicated that the mobility of bound water, extra-cellular water and free water in Pseudosciaena crocea increased after frozen by three methods , and the mobility increased in order of unfrozen sample, SF, QF-UTE and QF-LN. The content of bound water and extra-cellular water of the quick frozen samples were higher than that of SF treated samples, while free water content was lower than SF. Significant correlations were found between the NMR parameters and water holding capacity indices. The above results suggested that quick freezing caused greater changes in texture property and water holding capacity of fish flesh than SF, thus leading to higher juice loss and cooking loss after thawing, which was probably due to the cracking phenomena in the fish flesh during quick freezing.
