Alginate-gelatin systems are used in a wide range of applications, e.g., foods, cosmetics, drugs, and medicine. To target the techno-functionalities of alginate-gelatin systems such as texture, stability, or appearance it is necessary to understand the structure formation of gel systems, which is influenced by the molecular interactions and the phase behaviour. Therefore, the aim of this study was to characterise the molecular interactions and phase behaviour of dilute alginate-gelatin systems. For this purpose, we analysed alginate, gelatin A and their mixtures at pH 7. First, we characterised the effect of the sodium chloride concentration on the single polymer solutions by measuring the critical overlap concentration, the zeta potential, intrinsic viscosity, the Huggins coefficient as well as the molecular weight and the second virial coefficient. To gain a better understanding of the molecular interactions between alginate and gelatin, we determined the Huggins coefficient and the interaction parameter by Wolf as a function of mixing ratio, NaCl and urea concentration. Additionally, we calculated the second cross-virial coefficient. Lastly, we characterised the influence of the interactions on the secondary structure of gelatin by Fourier-transform-infrared-spectroscopy. The attractive interactions between alginate and gelatin potentially enabling the formation of soluble complexes, were demonstrated as deviations from additivity of intrinsic viscosity and negative cross-virial coefficients. Interestingly, the Wolf interaction parameter was affected by the NaCl concentration and the mixing ratio, whereas the presence of urea showed no impact. This indicates that the attractive interactions of alginate and gelatin A at pH 7 is rather caused by electrostatic interactions than hydrogen bonds. The present study clarifies the relevance of hydrogen bonds and electrostatic interactions as well as the impact of mixing ratio and solvent properties on the phase behaviour of alginate-gelatin systems. The insights contribute to a better understanding of the structure formation of concentrated alginate-gelatin systems, levelling the path to specific modifications of functionality.

藻酸盐-明胶系统用于广泛的应用，例如食品、化妆品、药物和医药。为了针对海藻酸盐-明胶系统的技术功能，如质地、稳定性或外观，有必要了解凝胶系统的结构形成，这受分子相互作用和相行为的影响。因此，本研究的目的是表征稀藻酸盐-明胶体系的分子相互作用和相行为。为此，我们在 pH 7 下分析了藻酸盐、明胶 A 及其混合物。首先，我们通过测量临界重叠浓度、zeta 电位、特性粘度、哈金斯系数以及分子量和第二维里系数。为了更好地了解藻酸盐和明胶之间的分子相互作用，我们确定了 Wolf 的 Huggins 系数和相互作用参数，作为混合比、NaCl 和尿素浓度的函数。此外，我们计算了第二个交叉维里系数。最后，我们通过傅里叶变换红外光谱表征了相互作用对明胶二级结构的影响。藻酸盐和明胶之间的有吸引力的相互作用可能导致可溶性复合物的形成，这被证明是与特性粘度的可加性和负交叉维里系数的偏差。有趣的是，Wolf 相互作用参数受 NaCl 浓度和混合比的影响，而尿素的存在则没有影响。这表明藻酸盐和明胶 A 在 pH 7 下的有吸引力的相互作用是由静电相互作用而不是氢键引起的。本研究阐明了氢键和静电相互作用的相关性以及混合比和溶剂性质对藻酸盐-明胶体系相行为的影响。这些见解有助于更好地理解浓缩海藻酸盐-明胶系统的结构形成，为功能的特定修改铺平道路。本研究阐明了氢键和静电相互作用的相关性以及混合比和溶剂性质对藻酸盐-明胶体系相行为的影响。这些见解有助于更好地理解浓缩海藻酸盐-明胶系统的结构形成，为功能的特定修改铺平道路。本研究阐明了氢键和静电相互作用的相关性以及混合比和溶剂性质对藻酸盐-明胶体系相行为的影响。这些见解有助于更好地理解浓缩海藻酸盐-明胶系统的结构形成，为功能的特定修改铺平道路。