Shrimp Cultured in Low-Salt Saline–Alkali Water has a Better Amino Acid Nutrition and Umami─Comparison of Flavors between Saline–Alkali Water- and Seawater-Cultured Litopenaeus vannamei

The advantages of Litopenaeus vannamei farming in saline–alkali water have gradually attracted attention, but few studies have focused on its flavor. In this study, L. vannamei cultured in saline–alkali water (SS) and ordinary seawater (CS) (both have a breeding time of 120 days) were selected for analysis (n = 5). High-performance liquid chromatography (HPLC) was used to measure free amino acids and flavoring nucleotides in the muscles of L. vannamei, while the taste activity value (TAV) and equivalent umami concentration (EUC) were used to analyze the degree of umami. The total essential amino acids (TEAA) in the SS group were 238.41 ± 46.24 mg/mL, significantly higher than that in the CS group (107.06 ± 15.65 mg/mL). The total amount of flavor nucleotides in the SS group was 2948.51 ± 233.66 μg/mL, significantly higher than those in the CS group (2530.37 ± 114.67 μg/mL). The content and TAV of some free amino acids (Glu, Cys-s) in the SS group were significantly higher. Meanwhile, due to the significant increase in IMP, the synergistic effect of free amino acids and flavored nucleotides leads to higher EUC. The significant separation of SS and CS samples in principal component analysis (PCA) indicates a significant difference between the two groups. Our results indicate that shrimp cultured in saline–alkali water has a stronger umami. This study enriches the basic theories related to the flavor of salt–alkali water crustaceans.