Microscopic insight into the interactions between pea protein and fatty acids during high-moisture extrusion processing

• Fatty acids induced exposure of protein hydrophobic groups during HME processing. • Linoleic acid limited the refolding of protein chains in the die. • Stearic acid enhanced the intermolecular disulfide bonds formation during cooling. • Unsaturated fatty acids inhibited the formation of anisotropic structures. To provide a theoretical basis for the quality improvement of plant protein-based meat substitutes with lipids, the interactions between pea protein and fatty acids (stearic, oleic and linoleic acids) and the effect on protein conformational changes during high-moisture extrusion (HME) processing were investigated using a dead-stop operation. The surface hydrophobicity analysis and Fourier transform infrared spectroscopy results revealed that the fatty acids induced the exposure of hydrophobic groups in the pea proteins, weakened hydrogen bonds, affected the aggregation of legumin subunits and promoted the conversion of α-helix and β-sheet structures to β-turn and random coil during HME processing. In the die, unsaturated fatty acids limited the refolding of protein chains and covalent interactions between proteins. Micromorphology analysis indicated that the coalescence of oleic and linoleic acids in the cooling zone hindered the formation of anisotropic structures while stearic acid promoted the formation of fibrous structures by enhanced disulfide bonds.