Abstract The effect of ultrasound pretreatment with mono-frequency ultrasound (MFU) and simultaneous dual frequency (SDFU) on rheology, texture, water holding capacity (WHC) and microstructure of whey protein emulsion gels was investigated. Also, the protein structure was displayed using circular dichroism and fluorescence spectrum. The Results showed that ultrasound could improve mechanical properties and change the microstructure of whey protein emulsion gel compared with the control. It was also found that, ultrasound could lead to decreasing in α-helix and increasing in random coil thereby exposing more tryptophan residues. As storage modulus (G'), texture hardness and WHC were negatively correlated with α-helix content, however, they had positive correlation with random coil content. Simultaneous dual frequency ultrasound exhibited the highest effect among the ultrasound pretreatments. It was indicated that the composite of oil droplet particulate aggregate network and protein aggregate network in the microstructure of emulsion gel might have resulted from enhanced molecular interactions of protein by ultrasound pretreatment. In conclusion, the dual frequency ultrasound was effective in improving the mechanical properties of whey emulsion gel when compared with the mono-frequency ultrasound.

中文翻译：

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单频和双频超声预处理对乳清蛋白乳液凝胶力学性能和微观结构的影响

摘要 研究了单频超声 (MFU) 和同步双频 (SDFU) 超声预处理对乳清蛋白乳液凝胶流变学、质地、持水能力 (WHC) 和微观结构的影响。此外，使用圆二色性和荧光光谱显示蛋白质结构。结果表明，与对照相比，超声可以改善乳清蛋白乳液凝胶的力学性能并改变其微观结构。还发现，超声可导致α-螺旋减少和无规卷曲增加，从而暴露更多色氨酸残基。由于储能模量（G'）、织构硬度和 WHC 与 α-螺旋含量呈负相关，而与无规卷曲含量呈正相关。同时双频超声在超声预处理中表现出最高的效果。表明乳化凝胶微观结构中油滴颗粒聚集网络和蛋白质聚集网络的复合可能是超声预处理增强蛋白质分子相互作用的结果。综上所述，与单频超声相比，双频超声能有效提高乳清乳液凝胶的力学性能。