Synergistic effects of UVA irradiation and phlorotannin extracts of Laminaria japonica on properties of grass carp myofibrillar protein gel

Abstract BACKGROUND Oxidized phlorotannin can be used as a protein crosslinking agent to produce high‐quality fish gel products. Phlorotannin can be easily induced to form quinone compounds in an oxidizing environment, while o ‐quinone has been proven to be a reactive, electrophilic intermediate that easily reacts with proteins to form rigid molecular crosslinking networks. The objective of this study was to investigate the synergistic effects of ultraviolet A (UVA) irradiation (1 h, 15 W m −2 ) and various concentrations of Laminaria japonica phlorotannin extracts (PTE) on the gel properties of grass carp myofibrillar protein (MP). RESULTS UVA treatment and PTE could synergistically improve the MP gel properties more than PTE alone ( P < 0.05). At 625 mmol kg −1 MP PTE alone, the gel strength and cooking yield reached 3.10 ± 0.16 g cm and 47.45 ± 0.35%, respectively, while with the same level of PTE plus UVA they became 4.26 ± 0.19 g cm and 53.89 ± 1.54%, respectively. The three‐dimensional network structure of the gel (with PTE + UVA) showed higher connectivity and tightness than that of the control group (no treatment). CONCLUSIONS The synergistic effects of PTE and UVA could effectively induce crosslinking of grass carp MP, which could lead to an improvement of MP gel quality. These findings would provide a new technical approach to produce high‐quality protein gel products in the fish processing industry. © 2020 Society of Chemical Industry