Functional, structural, and physicochemical properties of spray-dried abalone (<i>Haliotis discus</i> subsp. <i>hannai Ino</i>) protein and hydrolysates with varying degrees of hydrolysis

Abstract This study focused on preparing abalone protein hydrolysates from abalone muscle using papain and characterizing their functional, physicochemical, and structural properties. Abalone hydrolysates were stable in solubility across a hydrolysis degree range of 5.95%–14.46%. Hydrolysis notably enhanced foam capacity from 62% (Control) to 138% (APH-3). Emulsifying capacity and emulsion stability also improved significantly, increasing from 19.94 m2/g (Control) to 37.53 m2/g (APH-1) and from 19.59 min (Control) to 40.95 min (APH-1), respectively (p &amp;lt; .05). Moderate hydrolysis reduced protein molecular size, polydispersity index, and zeta potential, while increasing surface hydrophobicity, with APH-3 (DH 9.84%) showing the highest value. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed variations in protein composition with different hydrolysis degrees. Increased hydrolysis led to more disordered protein structures, affecting β-sheet, β-turn, and random coil proportions. Endogenous fluorescence and ultraviolet absorption intensities increased significantly (p &amp;lt; .05), whereas α-helix content and disulfide bonds decreased (p &amp;lt; .05). E-nose analysis indicated that hydrolysis degree significantly affected aromatic, hydride, alcohol, and methane aliphatic compounds. This study provides guidance for developing abalone protein hydrolysates with enhanced properties as potential functional foods.