Improved digestibility of β-lactoglobulin by pulsed light processing: a dilatational and shear study

Modifying the protein conformation appears to improve the digestibility of proteins in the battle against allergies. However, it is important not to lose the protein functionality in the process. Light pulse technology has been recently tested as an efficient non-thermal process which alters the conformation of proteins while improving their functionality as stabilizers. Also, in order to rationally design emulsion based food products with specific digestion profiles, we need to understand how interfacial composition influences the digestion of coated interfaces. This study has been designed to investigate the effects of pulsed light (PL) treatment on the gastrointestinal digestion of protein covered interfaces. We have used a combination of dilatational and shear rheology which highlights inter and intra-molecular interactions providing new molecular details on protein digestibility. The in vitro digestion model analyses sequentially pepsinolysis, trypsinolysis and lipolysis of β-lactoglobulin (BLG) and pulsed light treated β-lactoglobulin (PL-BLG). The results show that the PL-treatment seems to facilitate digestibility of the protein network, especially regarding trypsinolysis. Firstly, PL treatment just barely enhances the enzymatic degradation of BLG by pepsin, which dilutes and weakens the interfacial layer, due to increased hydrophobicity of the protein owing to PL-treatment. Secondly, PL treatment importantly modifies the susceptibility of BLG to trypsin hydrolysis. While it dilutes the interfacial layer in all cases, it strengthens the BLG and weakens the PL-BLG interfacial layer. Finally, this weakening appears to slightly facilitate lipolysis as evidenced by the results obtained upon addition of lipase and bile salts (BS). This research allows identification of the interfacial mechanisms affecting enzymatic hydrolysis of proteins and lipolysis, which demonstrates an improved digestibility of PL-BLG. The fact that PL treatment did not affect the functionality of the protein makes it a valuable alternative for tailoring novel food matrices with improved functional properties such as decreased digestibility, controlled energy intake and low allergenicity.