Effect of Freezing and Thawing Process on the Surface Color of Alfonsino

Abstract

The process of freezing and thawing causes the discoloration in the body surface of red-colored marine fishes such as alfonsino; which lowers their commercial values. The astaxanthin content and dispersion of erythrophore in the scale of alfonsino were measured to investigate the causes of the discoloration during freezing and thawing. Color measurement of the surface of alfonsino using the computer vision system showed that the discoloration during freezing and thawing was not affected by the storage period at –30 °C. In addition, there was little change in the astaxanthin content in the scale of alfonsino before and after freezing and thawing. The aggregation of erythrophores and damages to iridophores by freezing and thawing were confirimed by microscopic observations. These results demonstrated that the discoloration in alfonsino during freezing and thawing was caused not only by the oxidization and degradation of astaxantin, but also by the structural changes of the chromatophore in the scale.