Dietary <i>Phaffia rhodozyma</i> ‐Synthesized 3S, 3′S‐Astaxanthin Promotes Body Coloration and Muscle Quality in Pacific White Shrimp <i>Litopenaeus vannamei</i>

The focus of people on the yield of aquatic products has gradually shifted to superior quality. Astaxanthin is well-known for its superior antioxidant capacity, while research on its regulatory effect on muscle quality is limited. This study aims to investigate whether dietary <i>Phaffia rhodozyma</i>-synthesized 3S, 3'S-astaxanthin (L-AST) could promote the body coloration and muscle quality of <i>Litopenaeus vannamei</i>. Experimental diets with L-AST levels of 0, 30, 60, and 90 mg/kg were fed to <i>L. vannamei</i> (IBW: 2.72 ± 0.03 g) for 8 weeks. The results revealed that the shrimp fed L-AST diets presented better body coloration with decreased L ^<i>∗</i> values whereas increased a^∗ values and possessed higher levels of muscle astaxanthin. Dietary supplementation with 60 mg/kg L-AST significantly enhanced muscle texture (hardness, chewiness, resilience, and gumminess), which could be attributed to an increase in alkaline-insoluble collagen content and a decrease in myofiber diameter. Interestingly, dietary supplementation with 60 or 90 mg/kg L-AST markedly increased the content of glycine (a sweet amino acid) and total flavor amino acid (glutamic acid, aspartate, alanine, glycine). Further study showed that dietary supplementation with 60 or 90 mg/kg L-AST significantly improved free fatty acid profile by increasing contents of some monounsaturated fatty acids (C17:1n7, C18:1n9t and C24:1n9) and polyunsaturated fatty acids (C20:02 and C22:6n3). Taken together, dietary <i>P. rhodozyma</i>-synthesized L-AST considerably promoted muscle quality in <i>L. vannamei</i> by promoting histological and texture properties, elevating alkaline-insoluble collagen content while improving the profile of free amino acids and fatty acids.