title: Bioavailable level and source of cysteine determine protein quality of a commercial enteral product: adequacy of tryptophan but deficiency of cysteine for rats fed an enteral product prepared fresh or stored beyond shelf life.
abstract: Young rats were used in bioassays designed to assess the protein quality and tryptophan as well as cystine adequacy of the enteral product TwoCal-HN that was either freshly prepared or had been stored (nonrefrigerated) in a warehouse for 10 mo (i.e., beyond shelf life). Based upon supplementation studies, cystine was observed to be the first-limiting amino acid in both fresh and expired TwoCal-HN, and tryptophan was not second limiting. Protein efficiency ratio (PER) of expired, but not fresh, TwoCal-HN was lower than that of the casein control diet, but with cystine supplementation, PER of the TwoCal-HN products was equal to or greater than the PER of the casein control. With a diet containing 10 g protein/100 g that also contained energy-furnishing ingredients simulating TwoCal-HN, maximal growth enhancement occurred with a supplement of 1 g cystine/kg diet. Both glutathione and N-acetyl-L-cysteine were observed to be equivalent to an isomolar level of L-cystine in stimulating growth. Using a chemically defined amino acid diet that was singly deficient in tryptophan, bioavailability of tryptophan was determined for casein, fresh TwoCal-HN, expired TwoCal-HN and D-tryptophan. Slope-ratio bioefficacy values relative to L-tryptophan (weight gain regressed on supplemental tryptophan intake) indicated that none of the experimental sources of tryptophan had bioavailabilities different from 100%. The results indicated that tryptophan did not deteriorate, as measured analytically or biologically, as a result of storing TwoCal-HN beyond shelf life.(ABSTRACT TRUNCATED AT 250 WORDS)
authors: Department of Animal Sciences, University of Illinois, Urbana-Champaign 61801.
authors: D H
authors: DH
authors: Baker
authors: Y
authors: Y
authors: Han
mesh_terms: D000818:Animals; D001682:Biological Availability; D003545:Cysteine / Q000008:administration & dosage* / Q000172:deficiency / Q000493:pharmacokinetics; D004044:Dietary Proteins / Q000592:standards*; D005526:Food, Formulated / Q000592:standards*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D014364:Tryptophan / Q000008:administration & dosage* / Q000493:pharmacokinetics
chemical_list: D004044:Dietary Proteins; D014364:Tryptophan; D003545:Cysteine