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.

Wheat protein is one of the quality-determining factors of wheat malt. In the present study, wheat protein compositions and malt quality were determined to examine their correlation. During malting, gliadin and glutenin decreased, albumin and globulin increased and the wheat insoluble protein, especially glutelin, determined the dissolved degree of protein. As the wheat insoluble/soluble protein ratio increased, free α-amino nitrogen (FAN) of malt appeared to rise to a peak and then decreased significantly. FAN was the highest when the ratio was 2.23. With the increase in the insoluble/soluble protein ratio, extract, Kolbach index and saccharification time of the malt underwent a significant linear decrease (r=-0.934, 0.973 and 0.950, respectively). The research results indicated that the wheat protein content has to be in the range of 12.72-13.88% to obtain satisfactory wheat malt quality, and the insoluble/ soluble protein ratio should be in the range of 1.44-2.23.