Effect of protein oxidation on the structural characteristics of hazelnut protein isolate

Abstract

The oxidation and structural properties of hazelnut protein prepared from a low-temperature cold-pressed hazelnut meal were evaluated using three oxidative modification methods: AAPH (2,2'-azo(2-methylpropionamidine)dihydrochloride), MDA (malondialdehyde), and H 2 O 2 . The three different oxidants gradually increased the carbonyl content of the proteins, MDA from 1.91 to 8.87 nmol/m, AAPH (from 2.13 to 12.18 nmol/mg, and H 2 O 2 from 2.28 to 13.72 nmol/mg, indicating that the hazelnut protein was oxidized. The carbonyl content of H 2 O 2 -modified hazelnut proteins was the highest, implying that the proteins were more susceptible to oxidation by hydroxyl radicals. FT-IR, intrinsic fluorescence spectra, surface hydrophobicity, and protein electrophoresis implied that oxidative modifications altered the secondary structure of hazelnut proteins, and promoted protein aggregation and cross-linking. In addition, the oxidative modification resulted in a larger particle size distribution of hazelnut proteins and a decrease in the zeta potential absolute value, indicating a decrease in the hazelnut proteins stability and the formation of soluble aggregates. Overall, incubation with AAPH, MDA, and H 2 O 2 significantly affected the structure of hazelnut proteins, demonstrating that hazelnut proteins in food processing systems are susceptible to structural and property changes due to different oxidation products.