Impact of sorbitol on the thermostability and heat-induced gelation of bovine serum albumin

The influence of sorbitol (0–40 wt.%) on the thermal denaturation and gelation of bovine serum albumin (BSA, pH 7.0) in aqueous solution has been studied. The effect of sorbitol on heat denaturation of 0.5 wt.% BSA solutions was measured using ultrasensitive differential scanning calorimetry. The unfolding process was irreversible and was characterized by the thermal denaturation temperature (Tm). As the sorbitol concentration increased from 0 to 40 wt.%, Tm increased from 73.0 to 80.9 °C. The rise in Tm was attributed to the increased thermal stability of the globular state of BSA relative to its native state. The dynamic shear rheology of 4 wt.% BSA solutions containing 200 mM NaCl was monitored as they were heated from 30 to 90 °C at 1.5 °C min−1, held at 90 °C for 120 min, and then cooled back to 30 °C at −1.5 °C min−1. Sorbitol increased the protein gelation temperature (ΔTgel ∼+10 °C for 40 wt.% sorbitol), decreased the isothermal gelation rate at 90 °C, but increased the final shear modulus of the gels cooled to 30 °C. The impact of sorbitol on gel characteristics was attributed to its ability to increase protein thermal stability, increase the attractive force between proteins and decrease the protein–protein collision frequency.