Protein quality of high and low saponin alfalfa protein concentrate

The effects of saponin content, methionine content, and digestibility on the protein quality of alfalfa protein concentrates (APC) made from high and low saponin alfalfa were evaluated by chemical analyses and by rat bioassays. The protein quality of the APC both with and without added methionine were measured as protein efficiency ratios and as relative nutritive values (by a slope‐ratio assay). The low saponin APC had a higher crude protein content, a higher protein digestibility, a higher relative nutritive value, and higher protein efficiency ratios at all levels of added methionine than the high saponin APC. With the addition of 0.3% methionine the protein quality of the low saponin APC was as good as casein.