Beyond Covalent Cross-Linking: Drying History Governs the Physicochemical and Textural Properties of Bovine Blood Protein Gels

Abstract

We evaluated how the drying history (DH; freeze-drying vs. conventional oven-drying) of protein fractions from bovine blood affected their structural integrity and, consequently, the physicochemical and textural properties of the resulting heat-induced gels. DH was characterized by using Fourier Transform Infrared (FTIR) spectroscopy, X-ray diffraction (XRD), sulfhydryl (SH) exposure, and disulfide bond (S-S) formation. Functional properties included powder solubility, minimal gel concentration, gel hardness, and spontaneous syneresis. Results showed no correlation between covalent reticulation (disulfide bonds) and physical gel properties, indicating that non-covalent interactions drive the textural outcome. Furthermore, while conventional drying negatively affected cell fraction rehydration, the unexpected crystallization of endogenous NaCl in freeze-dried plasma was associated with superior rehydration and functional properties in the subsequent gels. These findings establish a direct link between the protein´s drying history and the final gel performance, providing essential knowledge for tailoring these sustainable protein precursors for specific food applications.