Formulation and Characterization of Food Hydrogels: Gelation Mechanisms, Dehydration Pathways, and Effects of Embedded Plant Cells.

The development of sustainable food systems increasingly relies on the valorization of agri-food by-products and circular economy strategies. In this context, food-grade hydrogels represent promising matrices for incorporating biological components and bioactive compounds. This study focuses on the preparation and characterization of four hydrogels formulated with natural biopolymers, such as pectin, an extract obtained from spray-dried by-products generated during the processing of strawberry and blueberry fruit preparations, with potential applications in innovative and sustainable food formulations. A specific formulation was produced by including plant cells. UV-visible spectra, pH, and moisture content of the hydrogels were evaluated. Their morphological, chemical, and hydrodynamic properties were investigated using micro-Raman and FTIR/ATR spectroscopy along with swelling degree and dehydration behavior over time. The analysis clarified gelation mechanisms, confirming the key role of calcium chloride in matrix stabilization and the influence of plant cells on water retention. The developed food-grade hydrogels demonstrated physicochemical stability, even after 20 days of storage at 4 °C. The incorporation of plant cells modulated the hydrogel's hygroscopic behavior, maintaining the fundamental gelation pathways. These results highlight the potential of these hydrogels as sustainable matrices for incorporating biological components and support their application in innovative food formulations based on the valorization of by-products.