Abstract: This study investigated the effect of L-lysine (at 0%–1.0%) on the quality characteristics of composite shrimp balls made from Pacific white shrimp and Antarctic krill. For comparison, 0.3% sodium tripolyphosphate (STPP) served as the control. The results showed that Lys addition significantly improved the sensory acceptability, texture properties, gel strength, water-holding capacity, and microstructure of composite shrimp balls. Shrimp balls with 0.6% Lys had the overall quality: the sensory evaluation score was the highest, at 85.01; the hardness, springiness, and chewiness increased markedly; the gel strength reached 1 213.64 g·mm; the water-holding capacity increased to 92.87%; the cooking loss decreased to 0.25%; the pH rose significantly. Low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) confirmed that adding 0.6% Lys significantly improved the water-holding capacity and proton density of the gel. Moreover, Lys promoted the formation of disulfide and hydrogen bonds between protein molecules, thereby attenuating hydrophobic interactions. Fourier transform infrared spectroscopy (FTIR) analysis corroborated that it enhanced intermolecular associations through affecting hydrogen bonding, thereby establishing a more compact and homogeneous three-dimensional gel network. Rheological analysis indicated that Lys effectively increased the storage modulus (G’) and loss modulus (G”) of shrimp surimi, thereby improving its viscoelasticity. In conclusion, Lys can be used as an effective natural gel modifier to replace STPP in composite shrimp balls, with a recommended addition level of 0.6%.

Key words: Antarctic krill; Pacific white shrimp; quality; gel properties; lysine; sodium tripolyphosphate