The effects of two types (energy-divergent/gathered) of ultrasound pretreatment of protein on the Maillard reaction of protein-hydrolysate from grass carp (Ctenopharyngodon idella) were studied. The test and analysis of Fourier transform infrared spectroscopy, surface hydrophobicity and atomic force microscopy of protein, peptide concentration, molecular weight distribution and free amino acid content of protein-hydrolysate were performed to reveal the mechanism. Also, the sensory characteristics of Maillard reaction products were evaluated. Results showed that Maillard reaction products presented higher absorbance value at 294 and 420 nm after pretreated by two types of ultrasound compared to that of control. The grafting degree value of products pretreated by energy-divergent ultrasound increased by 13.87%. Both of these two types of ultrasound pretreatment showed higher (p < 0.05) value of grafting degree compared to that of positive control (thermal denaturation). The random coil content and surface hydrophobicity of protein improved significantly (p < 0.05), and the depth distribution of protein molecules narrowed down after pretreated by ultrasound, especially energy-divergent type ultrasound. The change of protein structure increased small molecular peptide/amino acid content in protein-hydrolysate, so that it promoted the Maillard reaction process of protein-hydrolysate and glucose. The mouthfulness and overall acceptance of Maillard reaction products increased after pretreated by two types of ultrasound. Results indicated that ultrasound, especially energy-divergent type ultrasound pretreatment of protein was an effective method to promote Maillard reaction evolution of protein-hydrolysate from grass carp protein and improved the flavor of Maillard reaction products.

中文翻译：

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蛋白质超声预处理对草鱼蛋白水解物的美拉德反应的影响及其机理。

研究了两种超声（能量发散/聚集）蛋白质预处理对草鱼（Ctenopharyngodon idella）蛋白质水解产物的美拉德反应的影响。通过傅立叶变换红外光谱，蛋白质表面疏水性和原子力显微镜，肽浓度，分子量分布和蛋白质水解产物的游离氨基酸含量进行了测试和分析，以揭示其机理。此外，评估了美拉德反应产物的感官特性。结果显示，与对照组相比，经两种类型的超声波预处理后，美拉德反应产物在294和420 nm处呈现出更高的吸光度值。能量发散超声预处理的产品的接枝度值增加了13.87％。与阳性对照（热变性）相比，这两种类型的超声预处理均显示出较高的接枝度值（p <0.05）。蛋白质特别是能量发散型超声波处理后，蛋白质的无规卷曲含量和表面疏水性显着提高（p <0.05），蛋白质分子的深度分布变窄。蛋白质结构的改变增加了蛋白质水解物中小分子肽/氨基酸的含量，从而促进了蛋白质水解物与葡萄糖的美拉德反应过程。经两种类型的超声波预处理后，美拉德反应产物的口感和总体接受度有所提高。结果表明，超声