Influence of salts in the Hofmeister series on the physical gelation behavior of gelatin in aqueous solutions

The effect of various inorganic salts on the physical gelation behavior of the gelatin solutions was investigated by Fourier transform infrared (FTIR) spectrometer, polarimeter, rheometer, X-ray diffraction and differential scanning calorimetry. It was found that strongly hydrated anions, such as SO42− and H2PO4−, facilitated the gelation of the biopolymer solutions, evidenced by the increases of the length and content of triple helices. On the contrary, weak hydrated anions like Cl− and SCN− hindered the coil-helix transition of gelatin. Additionally, the gelling temperature (Tgel) of protein was directly correlated to the hydration entropy of anions, demonstrating that the elevation of Tgel was attributed to the strong hydration effect of kosmotropic anions. On the other hand, chaotropic anions lowered Tgel, due to the direct interactions of weak hydrated anions with polypeptide backbones which were confirmed by the FTIR results. These observations indicate that the gel structure can be modulated by Hofmeister salts. [Display omitted] •SO42− and H2PO4− enhance the gelation of gelatin through a hydration effect.•Cl− and SCN− hamper the gelation due to the binding of anions to polymer.•The effect of anions on Tgel followed the order of SO42− > H2PO4− > Cl− > SCN−.•The phase state of the polymer matrix remains unchanged with Hofmeister salts.