Effects of ultrasound-assisted alkaline extraction on the physiochemical and functional characteristics of chicken liver protein isolate
This research investigated the physiochemical and functional characteristics of chicken liver protein isolate, which was extracted by alkali (CLPI) and ultrasound-assisted alkali (UCLPI), respectively. Protein yield of UCLPI was increased by 55.4% over that of CLPI (P < 0.05). Several amino acids were significantly higher and methionine was lower in UCLPI (P < 0.05). Ultrasound treatment reduced the particle size and prolonged the stability of the protein isolate during 7 d storage. Lower pH and a higher amount of total solubilized proteins (68.5%) were found in UCLPI by comparison with CLPI (61.8%). Surface hydrophobicity increased greatly by 63.0% compared with CLPI, but the total/reactive sulfhydryl groups and the primary structure molecular weight profile between them were not significantly different (P > 0.05). However, the enthalpy of denaturation in UCLPI decreased by 41.7%, which was related to the changes in its second structure. This resulted in better water/oil holding capacity and emulsifying properties for UCLPI. The changed physiochemical characteristics and improved functional properties of UCLPI demonstrated the potential utilization of ultrasound-assisted alkaline extraction in the food industries.