Nutritional evaluation of Japanese abalone (Haliotis discus hannai Ino) muscle: Mineral content, amino acid profile and protein digestibility

[Display omitted] •Abalone muscle protein has high leucine and arginine.•Water-soluble fraction (WF) is rich in essential and umami amino acids.•The score of the first limiting EAA (tryptophan) in WF was more than 100%.•WF is more easily digested than the other fractions from abalone muscle. The chemical compositions and nutritional values of the water-soluble fraction (WF), myofibrillar protein (MP), and stroma protein (SP) from abalone muscle were investigated. The protein, carbohydrate, lipid, and ash contents of abalone muscle were 15.87, 6.36, 0.22, and 1.36 g/100 g, respectively. Most of the carbohydrates in the abalone muscle were released easily into water, and potassium was the most abundant mineral. WF and SP were rich in essential and umami amino acids, and all three fractions had high arginine contents. The essential amino acid index and predicted biological value of WF were 75.84 and 90.96, respectively. These values were considerably higher than those of MP and SP. Meanwhile, the predicted protein efficiency ratio of MP was the highest. Lysine was the first limiting essential amino acid (EAA) in MP and SP, and the score of the first limiting EAA (tryptophan) in WF was more than 100%. The in vitro protein digestibility of WF and SP was approximately 92% higher than that of MP. The in vivo experiments showed that WF was the easiest to digest. The nutritional value and high digestibility of WF can be claimed as a high-quality protein source based on the current findings.