Beta-lactoglobulin (b-Lg) was fractionated from whey protein isolate after precipitation of a-lactalbumin, bovine serum albumin, and immunoglobulins on pilot plant scale. The overall b-Lg concentration in the isolate was greater 98% and the average yield amounted to 70%. To improve interfacial properties, partial hydrolysis of b-Lg isolate was performed by trypsin, pepsin or alcalase under pH-stat conditions. Foaming of the b-Lg isolate and hydrolysate solutions with different incubation times was carried out. The studies showed that especially a limited peptic hydrolysis of b-Lg isolate led to both, increased overrun and superior foam stability, while foam drainage decreased by more than 50% in relation to foams produced by trypsin and alcalase treated hydrolysates. The superior foaming properties of peptic treated b-Lg may be due to the presence of large amounts of native, nonhydrolysable protein molecules, and surface-active peptides from a small amount of denatured protein molecules in the proteolysate. Practical applicationsProtein foams are an integral component of many foods. Beta-lactoglobulin (b-Lg) is the major whey protein of cow milk and determines the technofunctional properties of products like whey protein concentrates and isolates, which are available in large quantities on industrial scale. Therefore, it is useful to develop convenient processes of b-Lg isolation and modification of the isolate technofunctional properties. Costly technologies, like membrane filtration or ion-exchange chromatography processes are not needed to perform the convenient process developed. The advantage of peptic hydrolysis of b-Lg is its susceptibility in native state. Therefore, only denatured molecules are hydrolyzed leading to synergistic properties of peptides with strong surface activity and proteins with distinct foam stabilizing characteristics.