Evaluation of protein quality: comparison of single-point and multi-point assays

The quality of different protein sources having a wide spectrum of potential biological values has been assessed with multi-point and singly-point assays on growing Sprague-Dawley rats weighing 60 g. Values obtained with multi-point assays, expressed goth as absolute and relative values, were well correlated irrespective of the response parameter, i.e. as absolute and relative values, were well correlated irrespective of the response parameter, i.e. body weight change, body water or body nitrogen (r = 0.980). Single-point assay values based on body nitrogen content were also well correlated with the multi-point assays, but some discrepancies were noted for what assays based on body weight change was concerned. The modification of body protein concentration, in particular of rats fed the protein-free diet, was the main cause of these discrepancies. The problem of reference protein, when protein quality was expressed as relative value, was also discussed.