Formation Mechanism of Advanced Glycation End Products in Silver Carp Surimi Products during Freeze-thaw and Heating Treatment

Silver carp (Hypophthalmichthys molitrix) surimi was heated after freeze-thaw cycles at different freezing temperatures, and the changes of nonanal, 1-octene-3-alcohol, endogenous fluorescent substances, protein subunits, lysine, α-dicarbonyl compounds (glyoxal, GO and methylglyoxal, MGO), N^ε-carboxylmethyl-lysine (CML) as an advanced glycation end product (AGE) and fluorescent AGEs in surimi during freeze-thaw and heating treatment were determined. The results showed that freezing temperature had no significant effect on any of the parameters measured (P > 0.05). As the number of freeze-thaw cycles increased, the levels of nonanal, 1-octene-3-ol, endogenous fluorescent substances, CML and fluorescent AGEs in surimi increased significantly, the content of lysine increased, and the levels of GO and MGO decreased significantly (P < 0.05). The levels of 1-octene-3-ol, GO, MGO, CML and fluorescent AGEs increased significantly during heat processing, the content of lysine increased at first and then decreased, the level of endogenous fluorescent substances decreased significantly (P < 0.05), and the myosin heavy chain was gradually degraded into smaller proteins. The above results showed that freeze-thaw treatment provided a large number of precursors for the formation of AGEs in surimi. Thermal processing promoted fat oxidation and protein degradation, stimulating the formation of AGEs in surimi through various pathways, which could in turn affect the safety of surimi.