Effect of enzymatic hydrolysis and polysaccharide addition on the β-lactoglobulin adsorption at the air–water interface

Abstract

The effect of enzymatic hydrolysis and polysaccharide addition on the interfacial adsorption of β-lactoglobulin (β-LG) was investigated in this work. The enzymatic treatment was performed in the hydrolysis degree (HD) range of 0.0–5.0% using bovine α-chymotrypsin II immobilized on agarose beads. Anionic non-surface active polysaccharides (PS), sodium alginate (SA) and λ-carrageenan (λ-C) were studied in the concentration range of 0.0–0.5 wt.%. The adsorption process at the air–water interface was evaluated by means of tensiometry and surface dilatational rheology. Biopolymer interactions in solution were analyzed by extrinsic fluorescence spectroscopy. The enzymatic hydrolysis improved β-LG interfacial properties. On the other hand, at low HD (1.0%), PS addition enhanced surface and elastic properties of β-LG hydrolysate films probably due to a higher repulsion between biopolymers in solution. However, at high HD (3.0–5.0%), SA addition caused a deterioration of surface and elastic properties of β-LG hydrolysate films probably due to the segregation and hydrolysate aggregation in solution, whereas λ-C addition could promote the formation of soluble complexes leading to a better control of elastic properties of β-LG hydrolysate films.