Effect of fatty acid saturation degree on the rheological properties of pea protein and its high-moisture extruded product quality

To provide a deep insight into the application of lipid in plant protein-based meat substitutes through high-moisture extrusion (HME) process, the effect of fatty acid saturation degree (stearic acid, oleic acid and linoleic acid) on the rheological and structural properties of pea protein isolate (PPI), and its relationship with the extrusion system parameters and extrudate qualities were investigated. The oleic acid and linoleic acid significantly decreased the apparent viscosity of PPI dispersion and thus reduced the die pressure and torque during HME processing. Electrophoresis and Fourier transform infrared spectroscopy results revealed that fatty acids inhibited the aggregation of legumin and vicilin subunits at 50 and 20 kDa, and promoted the conversion of α-helix and β-sheet to β-turn and random coil. The macro- and micro-structure observation and texture analysis suggested that the fatty acids with higher unsaturation degree were not advantageous for the pea protein fibrous structure improvement during HME process.