Determination of cyclic dipeptides in extracts of katsuobushi (Dried Bonito) and other dried fishes
2017
Shimamura, T. (Kochi University, Nankoku, Kochi (Japan). Faculty of Agriculture and Marine Science) | Yamamoto, K. | Otsuka, Y. | Hayashi, M. | Kashiwagi, T. | Ukeda, H.
Cyclic dipeptides, which are also called 2,5-diketopiperazines (DKPs), have been known to occur in heated and fermented foods. Recently, DKPs have attracted attentions as bioactive components. Katsuobushi (dried bonito) is a major source of the traditional soup stock, which is essential to Japanese cuisine. It is produced by traditional production processes such as cutting, boiling, smoke drying, and molding. It can be considered as the heated and fermented food. In this study, DKPs in extracts of Katsuobushi and other dried fishes were determined. In addition, the relationship between the DKP content and production processes of Katsuobushi was investigated. The highest total amount of DKPs was recognized in Hongarebushi (Katsuobushi subjected to molding, 13.8ppm), followed by in frigate mackerel (10.8ppm), salmon (9.10ppm), and Arabushi (Katsuobushi dried without molding, 8.22ppm). On the other hand, DKPs were not detected in Japanese anchovy. Cyclo (-Ala-Pro) was the most predominant DKP in all analytical samples. During the production of Katsuobushi, the DKP content gradually increased. Especially, Pro-containing DKPs were contained abundantly. Cyclo (-Asp-Phe) and cyclo (-Leu-Trp) were only detected after molding. These results showed that both heat treatment and molding are responsible for DKP formation in Katsuobushi production.
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