Effects of ultrasound assisted extraction on the physiochemical, structural and functional characteristics of duck liver protein isolate

[Display omitted] •Isolate by ultrasound (UDLPI) increased the protein yield over control (DLPI).•Surface hydrophobicity of UDLPI increased by 39.5% as compared to DLPI.•Particle size of UDLPI reduced by 12.3% with a narrower size distribution.•UDLPI showed partial protein hydrolysis and unfolding by spectroscopy analysis.•UCLPI demonstrated better solubility and foaming expansion than DLPI. This work investigated the impact of ultrasound assisted extraction on the physicochemical, structural and functional properties of duck liver protein isolate (UDLPI). Degreased liver powders were extracted by ultrasound working at a single frequency of 24kHz and a fixed power of 266W by a pulsed on-time of 2s and off-time of 3s for 42min in pH11.2 solution. The results revealed that UDLPI yield and the protein content increased by 67.7% and 4.6% respectively compared to that of the conventional alkaline extraction (DLPI). Ultrasound treatment could cause partial protein hydrolysis and unfolding as suggested by differential scanning calorimetry, circular dichroism and fluorescence spectroscopy analysis, leading to increased surface hydrophobicity, surface net charge and gelling property. The particle size reduced from 177.8nm of DLPI to 156.0nm of UDLPI. Ultrasound also promoted the storage modulus (G′) and solubility of the isolate. Moreover, the foaming expansion was especially strong, compared to DLPI. However, the results of the foam stability, reactive-/total-sulfhydryl groups and sodium-dodecyl sulfate-polyacrylamide gel electrophoresis showed no significant change between UDLPI and DLPI (P>0.05). Therefore, UDLPI with better functional property could be utilized as new materials in the food industry.