The effects of limited enzymatic hydrolysis on the physicochemical and emulsifying properties of a lentil protein isolate

The physicochemical and emulsifying properties of lentil protein isolates (LPI) were investigated as a function of their degree of hydrolysis (DH of 4, 9 and 20%) following exposure to trypsin/heat. Specifically, interfacial tension, surface characteristics (charge and hydrophobicity) and intrinsic fluorescence were determined. These parameters were then related to changes in the emulsification activity (EAI) and stability indices (ESI) of unhydrolyzed (u-LPI) and hydrolyzed LPI (h-LPI) in a flaxseed oil–water emulsion. Interfacial tension was found to decrease from ~6.5 to ~6.1mN m−1 for u-LPI and h-LPI (DH 4–20%), respectively. A similar trend was observed for surface hydrophobicity, which declined from ~30 to ~24 for the u-LPI and h-LPI (DH 4–20%), respectively. In contrast, surface charge values were similar for all materials (~−37mV). Intrinsic fluorescence as a function of emission wavelengths (300–400nm) indicated a slight change in the tertiary conformation of LPI upon hydrolysis, where the magnitude of fluorescence intensity declined relative to that of u-LPI. Changes in physicochemical properties upon hydrolysis had a detrimental effect on EAI and ESI values, which declined from ~51 to ~47m2g−1 and ~12 to ~11min for u-LPI and h-LPI (DH 4–20%), respectively. ► Limited hydrolysis of lentil proteins negatively impacted emulsifying properties. ► Limited hydrolysis of lentil proteins led to a decrease in surface hydrophobicity. ► Physiochemical and emulsifying properties were similar over the DH range of 4–20.