Dialysis Cell for the In Vitro Measurement of Protein Digestibility

A dialysis cell was devised to study in vitro digestion of proteins. The inner reaction vessel (surrounded by a tubular membrane with molecular weight cutoff of 1000) was fixed into a cylindrical outer compartment where buffer circulation was provided. The dimensions of compartments, membranes and buffer flow rate were determined with labelled amino acids in order to ensure the most efficient diffusion pattern. For the digestion assay, casein was first hydrolyzed with pepsin (pH 1.9) for 30 min. The mixture was then made alkaline (pH 7.5) and poured into the dialysis tube with pancreatin. Nitrogenous material collected with the sodium phosphate buffer was analyzed without further fractionation for the direct measurement of hydrolysis kinetic or of protein digestibility.