Evaluation of Factors Affecting Protein Quality as Well as Lysine and Sulfur Amino Acid Bioavailability of Commercial Enteral Products

114 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1988.Rat bioassays were conducted to evaluate protein quality as well as lysine (LYS) and sulfur amino acid (SAA) bioavailability in three commercial enteral products as affected by the severity of heat processing during sterilization, carbohydrate composition and storage of the products for 1 year. When evaluated fresh, the enteral products Osmolite HN and Ensure were lower in protein quality than casein, as determined by protein efficiency ratio (PER), regardless of heat treatment. With addition of the limiting amino acid, cystine, PER's of both Osmolite HN and Ensure were improved significantly (p $$ 0.05) on PER, even though all had darkened in color. Slope-ratio regression analysis (weight gain regressed on supplemental LYS intake) yielded LYS bioavailability estimates of 94.4% and 105.9%, respectively, for Osmolite HN and Ensure. The most severe heat treatment of Ensure decreased LYS bioavailability by 10% relative to the Ensure control. Partitioning weight gain into that resulting from LYS consumed in the basal diet and that resulting from the LYS supplement per se provided higher estimates of LYS bioavailability (i.e., 100% and 110% LYS bioavailability for Osmolite HN and Ensure, respectively). With storage, LYS bioavailability decreased by 10% in Osmolite HN and Ensure. LYS bioavailability of Ensure Plus was virtually 100% and was not affected by either carbohydrate composition or heat treatment. Storage of the Ensure Plus products for 1 year resulted in a 10% decrease in LYS bioavailability of those products containing greater concentrations of reducing sugars. SAA bioavailability of Ensure and Ensure Plus was 93.9% and 100.0%, respectively, relative to crystalline SAA. SAA bioavailability was not affected by heat treatment, carbohydrate composition or storage. Thus, although there was a 10% decrease in LYS bioavailability with storage of the enteral products evaluated, overall protein quality and SAA bioavailability (the protein quality-limiting factor) were not affected by storage, heat treatment or carbohydrate composition. Therefore, the decrease in LYS bioavailability is of minimal nutritional significance.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD