Improving the functionality and biological properties of Iranian date palm (Phoenix dactylifera L) seeds protein with different proteases

Abstract

In this study, date seeds as a major agricultural by-product were utilized for production of antioxidant peptides with techno-functional properties. Date seeds protein (DSP) was extracted and hydrolyzed by different enzymes (Alcalase, trypsin, pancreatin and pepsin). Then, the degree of hydrolysis (DH), amino acid composition, functional characteristics (e.g., solubility, and water- and oil-holding capacity), free radical inhibiting activity, reducing power, total antioxidant activity (TAA) and metal ion chelating activity of the hydrolysates (DSPHs) were examined. Chemical analysis of the obtained protein concentrate (∼ 65 %) indicated the presence of amide A and B regions. Also, amide I to III regions and secondary structures (α-helix, β-sheet, β-tern and random coils) were observed in the extracted DSP-protein. The DH and essential amino acids content of DSPHs were affected by enzyme type. The hydrolysis treatments resulted in a significant increase in the solubility of DSP, particularly in acidic pH levels and around its isoelectric point. In comparison to DSP, DSPHs also exhibited higher inhibitory activity against free radicals such as DPPH (72.5 %), ABTS (92.5 %), OH (64.5 %), and NO (57.9 %). Furthermore, DSPHs demonstrated greater reducing power (1.84), TAA (2.3), and enhanced chelating activity towards iron (73.2 %) and copper (40.1 %) transition ions. Various factors, including DH and the composition of amino acids, especially the amount of charged, hydrophobic, and antioxidant types, have played a crucial role in these outcomes. With their significant nutritive, functional, antioxidant, and metal ion chelating activities, DSPHs can serve as a natural additive to enhance the nutritional value and stability of various food products.