Rare sugars are monosaccharides and their derivatives that are not commonly found in nature. d-Allulose is a rare sugar that is C-3 epimer of fructose and presents an alternative to sucrose with potential health benefits. In this study, different amounts of sucrose, d-allulose, and soy protein isolate (SPI) were used to prepare a set of pectin gels. The effect of these ingredients on the gels was studied at both a molecular level, by ¹H nuclear magnetic resonance (NMR) relaxometry, and a macroscopic level, through the assessment of viscoelastic properties as well as hardness and moisture content measurements. The NMR dispersion profiles were analyzed considering relaxation mechanisms associated with rotational and translational diffusion motions of mono- and disaccharides as well as bound water molecules. Significant variations of the local diffusion coefficient for the studied formulations were evidenced by the model fitting analysis. The viscosity trends observed within each group of samples having the same amount of SPI were mostly in agreement with the diffusion coefficients obtained from the NMR relaxometry. The observed discrepancies could be explained considering hardness and moisture content results, which put into evidence the fact that decreasing the moisture (mainly free water) affects the macroscopic properties of the systems, such as hardness and viscosity, but not the local diffusion processes probed by NMR relaxometry. These findings show the importance of combining both micro- and macroscopic information to analyze the different properties of food products.

中文翻译：

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果胶基凝胶的表征：1H 核磁共振弛豫研究

稀有糖是自然界中不常见的单糖及其衍生物。d-阿洛酮糖是一种罕见的糖，是果糖的 C-3 差向异构体，是蔗糖的替代品，具有潜在的健康益处。在本研究中，使用不同量的蔗糖、d-阿洛酮糖和大豆分离蛋白 (SPI) 来制备一组果胶凝胶。这些成分对凝胶的影响在分子水平上进行了研究，通过¹H 核磁共振 (NMR) 弛豫测量法和宏观水平，通过评估粘弹性以及硬度和水分含量测量。考虑与单糖和二糖以及结合水分子的旋转和平移扩散运动相关的弛豫机制，分析了 NMR 分散曲线。模型拟合分析证明了所研究配方的局部扩散系数的显着变化。在具有相同 SPI 量的每组样品中观察到的粘度趋势大多与从 NMR 弛豫法获得的扩散系数一致。考虑到硬度和水分含量结果，可以解释观察到的差异，这证明降低水分（主要是游离水）会影响系统的宏观特性，例如硬度和粘度，但不会影响 NMR 弛豫测量法探测的局部扩散过程。这些发现表明了结合微观和宏观信息来分析食品不同特性的重要性。