Differences in Amino Acid Digestibility and Protein Quality Among Various Protein Isolates and Concentrates Derived from Cereal Grains, Plant and Dairy Proteins

Abstract

Abstract Objectives The objectives of this research were to use the growing pig as a model to determine the amino acid (AA) digestibility and protein quality by the digestible indispensable amino acid score (DIAAS) for brown rice concentrate (BRPC), pea protein concentrate (PPC), two rapeseed protein isolates (RSP-1 and RSP-2), soy protein isolate (SPI), and whey protein isolate (WPI). Methods Seven ileal cannulated barrows (36.5 ± 1.6 kg) were randomly allotted to a 7 × 7 Latin square design with 7 diets and seven 7-d periods, with ileal digesta collected on d 6 and 7. Each protein ingredient was included in a diet as the only AA containing source, and a nitrogen-free diet was used to measure basal endogenous losses of AA. The DIAAS were calculated for children from 6 months to 3 years and for persons > 3 years according to the Food and Agriculture Organization. Data were analyzed using the PROC MIXED of SAS in a completely randomized design with the pig as the experimental unit. Results The standardized ileal digestibility (SID) of Arg, His, Ile, Leu, and Phe was greater (P < 0.05) for WPI compared with the other proteins, and the SID of Thr and Trp did not differ among WPI, SPI, and RSP-2. The SID of all indispensable AA (IAA), expect Arg and Lys, was greater (P < 0.05) for RSP-2 than for PPC and BRPC, and PPC and BRPC had a greater (P < 0.05) SID of most IAA, expect His, Lys, and Met, than RSP-1. For DIAAS, RSP-2 had a DIAAS greater than 100 for children 6 months to 3 years, whereas, for persons > 3 years, RSP-2 and WPI had DIAAS greater than 100, i.e., 110 and 117, respectively. For both reference patterns, the DIAAS for RSP-2 and WPI was greater (P < 0.05) than for SPI, and the DIAAS for RSP-1 was less (P < 0.05) than the DIAAS for SPI but greater (P < 0.05) than for PPC, and PPC had a DIAAS greater (P < 0.05) than BRPC. Conclusions Results of this research illustrate that WPI is an excellent dairy protein for persons >3 years, and RSP-2 is an excellent quality plant protein for children from 6 months to 3 years and persons >3 years. In contrast, protein concentrates from cereal grains and some plant proteins, i.e., BRPC and PPC, respectively, are lower quality proteins, but soy based plant protein isolates, i.e., SPI, may be considered good quality proteins for children from 6 months to 3 years and persons >3 years. Funding Sources DSM animal nutrition and health.