Abstract
BACKGROUND: Salmon products are excellent foods that contain indispensable nutrients including fatty acids and amino acids (AA), but during processing, salmon co-products that cannot be used for the primary purpose are also generated. Examples of such co-products include salmon protein hydrolysate concentrate (SPHC) and salmon protein hydrolysate isolate (SPHI), but there is no information about the protein quality of these co-products. Therefore, the objective of this experiment was to use the digestible indispensable amino acid score (DIAAS) method to test the hypothesis that the protein in SPHC and two sources of SPHI (SPHI1 and SPHI2) can supplement lower-quality proteins. RESULTS: For children from 6 months to 3 years old and individuals older than 3 years, SPHC had greater (P < 0.05) DIAAS than SPHI1 and SPHI2, and SPHI2 had greater (P < 0.05) DIAAS than SPHI1. For children from 6 months to 3 years, leucine was the first limiting AA in SPHC, and tryptophan was the first limiting AA in SPHI1 and SPHI2. For individuals older than 3 years, there was no limiting AA (DIAAS ≥ 100) for SPHC, but for SPHI1 and SPHI2 leucine was the first limiting AA. CONCLUSION: All sources of salmon protein hydrolysates had excellent AA digestibility, and SPHC can be used to compensate for lower protein quality in other ingredients to produce a balanced diet that meets requirements for all indispensable AA for individuals older than 3 years. © 2026 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.