Changes in chemical and sensory properties of migaki-nishin (dried herring fillet) during drying.

Migaki-nishin is a Japanese term that refers to dried herring fillets. It is widely consumed in Japan due to its characteristic flavor enhancing properties. This study was conducted to investigate the changes in chemical and sensory properties of migaki-nishin during drying. Chemical analyses showed that extractive nitrogen and amount of peptides increased significantly (P < 0.05) up to the 8th day of drying and then slightly decreased by the 10th day. Glutamic acid, alanine, glycine, and histidine were the most abundant free amino acids and the largest increase was found in samples dried for 10 d. A decrease in Hunter's L* value (lightness) and increase in b* value (yellowness) as well as browning intensity suggested that nonenzymatic browning occurred in migaki-nishin during drying. Fluorescence spectrophotometric determination also revealed that Maillard reactions progressed throughout the drying period. In addition, available lysine content and free amino groups decreased significantly (P < 0.05) as drying progressed. Sensory evaluation showed that addition of water-soluble extracts to Japanese noodle soup (mentsuyu) linearly enhanced the flavor characteristics such as thickness, mouthfulness, and continuity with the increased length of drying time. These results suggest that during the drying period, proteolysis as well as Maillard reaction products increased markedly, which might contribute to the characteristic taste and flavor of migaki-nishin.