Physicochemical and functional characteristics of Eucommia ulmoides seed meal protein hydrolysates and their isolates

Eucommia ulmoides Oliv. seed meal (ESM) as a potential edible protein source as this by-product is usually underutilized or discarded. This study aimed to isolate antioxidant ESM protein hydrolysates (ESMHs) fractions and investigate their physicochemical properties to explore their potential applications.

Three fractions (F1, F2, F3) were isolated via gel chromatography, showing a positive correlation between the antioxidant capabilities and their antioxidant amino acids composition. Fluorescence spectra revealed a red shift of 3-6 nm in the maximum emission wavelength (λ_max) for the fractions compared to ESMHs, indicating increased exposure of aromatic amino acids on the side chains of F1, F2, and F3 isolates. The surface hydrophobicity (H₀) index for these isolates followed the order: F2 > F3 > F1, aligning with their endogenous fluorescence spectra data. These findings further verified that more hydrophobic amino acid residues were exposed as a result of the structural unfolding of proteins. Thermal stability analysis demonstrated that the isolated fractions with higher H₀ required less energy for denaturation. A distinct taste difference was observed between isolated fractions and ESMHs, tyrosine, phenylalanine, histidine and arginine were closely associated with the taste generation. Additionally, the low molecular weight and high glutamic acid content of the isolated fractions would contribute to their umami taste.

The present study demonstrated that ESMHs and their isolated fractions possessed desirable functional properties, including antioxidant capacity and favorable taste profiles, thereby presenting significant potential as functional ingredients for food, cosmetics or pharmaceuticals industries. © 2025 Society of Chemical Industry.