Fermented skim milk is an ideal food for consumers such as diabetic and obese patients, but its low-fat content affects its texture and viscosity. In this study, we developed an effective pretreatment method for fermented skim milk using low-frequency ultrasound (US), and investigated the molecular mechanism of the corresponding quality improvement. The skim milk samples were treated by optimal ultrasonication conditions (336 W power for 7 min at 3 °C), which improved the viscosity, water-holding capacity, sensory attributes, texture, and microstructure of fermented skim milk ( < 0.05). Further mechanistic analyses revealed that the US treatment enhanced the exposure of fluorescent amino acids within proteins, facilitating the cross-linking between casein and whey. The increased surface hydrophobicity of fermented milk indicates that the US treatment led to the exposure of hydrophobic amino acid residues inside proteins, contributing to the formation of a denser gel network; the average particle size of milk protein was reduced from 24.85 to 18.06 µm, which also contributed to the development of a softer curd texture. This work is the first attempt to explain the effect of a low-frequency ultrasound treatment on the quality of fermented skim milk and discuss the molecular mechanism of its improvement.

中文翻译：

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超声波预处理对脱脂发酵乳品质的影响及改进机制


发酵脱脂奶是糖尿病和肥胖患者等消费者的理想食品，但其低脂肪含量影响其质地和粘度。在本研究中，我们开发了一种使用低频超声（美国）对发酵脱脂奶进行有效预处理的方法，并研究了相应质量改善的分子机制。脱脂乳样品经过最佳超声波处理条件（336 W 功率，3 °C，7 分钟），改善了发酵脱脂乳的粘度、持水能力、感官属性、质地和微观结构（< 0.05）。进一步的机理分析表明，美国处理增强了蛋白质内荧光氨基酸的暴露，促进酪蛋白和乳清之间的交联。发酵乳表面疏水性增加表明US处理导致蛋白质内部疏水性氨基酸残基暴露，有助于形成更致密的凝胶网络；牛奶蛋白的平均粒径从 24.85 微米减小到 18.06 微米，这也有助于形成更柔软的凝乳质地。本工作首次尝试解释低频超声处理对发酵脱脂奶品质的影响，并探讨其改善的分子机制。