Recovery of essential amino acids in protein mineral concentrates at electrophysical processing of whey

Abstract

High biological or nutritional value of whey proteins is due to an elevated content of such amino acids as essential, conditionally essential or functional ones. It is known that whey proteins make up about 20% of milk proteins. The remaining 80% is casein. But comparing the amino acid profile of these two milk protein fractions shows that whey proteins contain a higher amount of essential amino acids and branched-chain amino acids that are physiologically extremely important and confer whey proteins an important biological value. More than 50% of amino acids in whey proteins are essential or conditionally essential ones. The study of the former ones was the purpose of this work. The variations in the content of amino acids in protein-mineral concentrates (PMCs) at different processing regimes have been investigated by the authors. Two types of whey were the objects of study: after the manufacture of the granulated cottage cheese „Grauncior‖ (called whey with high protein content, or HWPC) and that after the manufacture of the ―Cottage cheese‖, 2% fat content (called whey with medium protein content, or MWPC), in the membrane electrolyzer EDP-4, at j=10 and 20 mA/cm2, at the stationary regime. All PMCs were collected every 5 minutes; the ratio of the volume of the processed whey (V) to the surface of the electrodes (S) V/S is 1. The level of recovery of each essential amino acid in the PMCs depends on the time of electrophysical processing, on the current density, on pH and temperature values. The parameters for the optimal isolation of each amino acid are: for HWPCs Tre (threonine), Val (valine), Ile (isoleucine), Leu (leucine), Phe (phenyalanine), and His (histidine) - current density j=20 mA/cm2, for 10 min., pH=11.6 and tºC=29.5 ºC; for HWPC Trp (tryptophan) - current density j=10 mA/cm2, for 5 min., pH=12.1 and tºC=28ºC; for HWPC Lysine (Lys) - current density j=20 mA/cm2, for 5 min., pH=8.5 and tºC=24.5 ºC; for HWPC Arg (arginine) – current density j=20 mA/cm2, for 15 min., pH=11.6 and tºC=35 ºC. As to MWPC Met (methionine), the most appropriate parameters are – current density j=10 mA/cm2, for 20 and 25 min., pH=11.8 and tºC=25 ºC. To sum up: the established parameters for the optimal isolation of the studied amino acids are necessary to highlight the nutritional importance of essential amino acids, which makes whey protein a premier protein for a variety of food formulations to meet or exceed dietary recommendations for essential amino acids.