Investigation of Pectin-Water Interactions: A Practical Approach

Pectin-water interactions are crucial for pectin production, transport, storage and application. Pectin is hygroscopic and during dissolution often lumps with a powder core and a gel-like surface are formed which are hardly to dissolve afterwards. Water can be sorbed to the powder also from the environment by gas diffusion during transport and storage or can be added by fluidization in order to induce better dissolution properties by agglomeration. A modified sorption and the capillary sucking method have been tested for several different types of demethoxylated pectins and a significant influence of the modification parameters on pectin-water interactions was found. In general, acidic treated pectins showed low water sorption by gas diffusion but high water uptake and delayed dissolution by capillary sucking. Enzymatically demethoxylated pectins, in contrast, sorbed more water from wet air but showed less water uptake by capillary sucking and started to dissolve earlier. The differences can be explained by the conditions during demethoxylation, especially pH and also enzyme type. The resulting more or less strong intermolecular interactions between neighboured demethoxylated pectin macromolecules were trapped during drying. They determined pectin molecular parameters and particle morphology and, thus, pectin water interactions. The results of the presented investigations are of general importance not only for pectins and their application but also for other comparable food hydrocolloids.