Separation and characterization of β-lactoglobulin and α-lactalbumin from whey and whey protein preparations

Abstract

The properties of β-lactoglobulin (β-Lg) and α-lactalbumin (α-Lac) prepared from commercial samples of liquid whey (LW), whey protein isolate (WPI), or whey protein concentrate (WPC), using the same fractionation process, were studied. The process was based on β-Lg solubility at low pH in the presence of salt, on the weak calcium binding capacity of α-Lac below pH 3.9, and on the ease of chelating the calcium with calcium sequestrants, causing destabilization and precipitation of the calcium-free form of α-Lac. Sodium citrate (NaC) and sodium hexametaphosphate (SHMP) were more effective for the separation of β-Lg and α-Lac from the whey protein sources than the other tested chelating agents. Recoveries of 47–69% of β-Lg originally present in the whey preparations were recorded, with purities ranging from 84% to 95%, and protein contents ranging from 40% to 99%, depending on the source of whey protein and type of chelating agent. The yields of α-Lac in α-Lac fractions obtained without pH adjustment were 23–89%, with purities ranging from 83% to 90%, and protein contents ranging from 65% to 96%; the yields of α-Lac in α-Lac fractions obtained with adjustment to pH 7.5, were 11–43%, with purities ranging from 68% to 73%, and protein contents ranging from 44% to 81%. The ash contents of some protein fractions were relatively high. Glycation was detected in the proteins, with the highest degree of glycation in the proteins from WPC, resulting in higher molecular weights of the proteins from WPC when compared with those from LW and WPI.