凍結乾燥魚肉の変色について

Abstract

The development of discoloration in foods is a serious problem, because such an undesirable change is intimately associated with the chemical reactions resulting in “off” flavor. In an attempt to elucidate the mechanism of the discoloration in fish products, the authors studied on the respective discoloration of lyophilized white muscle and dark muscle of jack mackerel (Trachurus japonicus (TEMMINICK and SCHLEGEL)) during the storage with the view to research myoglobin change, oil oxidation and MAILLARD reaction. The changes of reflectance spectra during the storage indicated that myoglobin change scarcely influenced the discoloration, though myoglobin occurred in the lyophilized muscle (Figs. 1, 2). Comparing the reflectance spectra with each other in model systems where lyophilized and defatted muscle was autoclaved or added with fresh oil, the authors found that the discoloration by MAILLARD reaction and that by oil oxidation were analogous to that of the intact lyophilized muscle during the storage (Figs. 3, 4, 5 and 6). These facts suggested that the evaluation of the discoloration rate in the lyophilized muscle was able to be made by using R410×100/(R450)2, which has been posturated as an indication of the browning rate caused by MAILLARD reaction. By the evaluation, it was concluded that the discoloration of dark muscle was chiefly contributed by oil oxidation, on the other hand, the discoloration of white muscle was largely contributed by MAILLARD reaction, and the rate of the former was much higher than that of the latter (Fig. 7 and Table 1). Concerning to the discoloration by oil oxidation, it is interesting that the reaction between oxidized oil and volatile basic nitrogenous compound such as trimethylamine did not play any important role in the discoloration (Table 1).