Effects of salt concentrations on the advanced glycation end-products in dried salted spanish mackerel fillets during storage

Contents of protein-bound advanced glycation end-products (AGEs) including Nε-carboxymethyl-lysine (CML) and Nε-carboxyethyl-lysine (CEL), as well as total viable counts (TVC), total volatile basic nitrogen (TVB-N) and thiobarbituric acid reactive substances (TBARS) in vacuum-packed dried salted Spanish Mackerel fillets previously brined with 0‒15% NaCl during storage at 25 °C were determined. In freshly dried fish fillets with increased salt concentration, TVB-N decreased from 39.32 ± 5.39 to 22.35 ± 4.55 mg N/100 g and TBARS increased from 0.18 ± 0.01 to 0.50 ± 0.03 mg MDA/kg. No statistical differences were found in the levels of TVC, CML and CEL of dried fish (P= 0.215‒0.645). TVC and TVB-N levels of the dried salted fish fillets increased during 25 d storage (P= 0.000‒0.036), but reduced with increase of NaCl concentration (P= 0.000‒0.002). TBARS levels of the fillets increased until day15 and then slightly declined (P= 0.000‒0.036). Salt promoted the increase in TBARS in dried fish but showed inhibition effect with higher concentrations (P= 0.000‒0.003). Levels of protein-bound CML and CEL in both unsalted and salted fish fillets increased constantly during storage (P= 0.000‒0.050), whereas NaCl of increased content inhibited the formation of protein-bound CML and CEL in fillets (P= 0.000‒0.119). Positive correlations were observed in the contents of protein-bound CML and CEL with TVC, TVB-N and TBARS (r = 0.445‒0.839, P= 0.000‒0.002), indicating the formation of protein-bound AGEs in dried fish fillets is attributable to protein deterioration and lipid oxidation during storage.