In vitro assay for protein digestibility: interlaboratory study.
True protein digestibilities of 17 protein sources were estimated by 6 laboratories using an in vitro, 3-enzyme digestion system in a pH stat. Samples from animal, vegetable, and mixed food sources were freeze-dried (if not already dried), ground, mixed, and shipped to each collaborator along with a sodium caseinate standard and trypsin, chymotrypsin, and peptidase. The uptake of titrant during enzymatic digestion was used to calculate estimates of digestibility. Digestibilities ranged from 100% for casein to 89.9% for whole wheat cereal. Mean relative standard deviations for repeatability were 1.4% for rolled oats and less than 1% for the remaining 16 samples. Mean relative standard deviations for reproducibility ranged from 5.0 to 0.8%; values were less than 2.5% for 13 of the 17 samples.
U.S. Department of Agriculture, Beltsville Human Nutrition Research Center, Beltsville, MD 20705.
F E
FE
McDonough
G
G
Sarwar
F H
FH
Steinke
P
P
Slump
S
S
Garcia
S
S
Boisen
D000818:Animals; D002364:Caseins / Q000032:analysis; D002918:Chymotrypsin; D004044:Dietary Proteins / Q000032:analysis*; D004527:Egg Proteins / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D008460:Meat / Q000032:analysis; D009584:Nitrogen / Q000032:analysis; D010447:Peptide Hydrolases; D014357:Trypsin; D014675:Vegetables / Q000032:analysis
D002364:Caseins; D004044:Dietary Proteins; D004527:Egg Proteins; D010447:Peptide Hydrolases; D002918:Chymotrypsin; D014357:Trypsin; D009584:Nitrogen