The rheological properties and gelation kinetics of corn starch/bovine serum albumin blend

Abstract

The rheological properties and gelation kinetics of corn starch (CS)/bovine serum albumin (BSA) blends were investigated using the mass ratio of [CS]/[BSA] of 0, 0.5, 1, 2, and 3. The results from the temperature ramp and time sweep tests within linear viscoelastic regime showed a decrease in the gelation temperature (Tgel) and gelation time (tgel) of the BSA with increasing the mass ratio of [CS]/[BSA]. A significant decrease in the Tgel and tgel occurred at 5 wt.% BSA with [CS]/[BSA] = 3, where about 12 °C and 11 min drops in the Tgel and tgel were recorded. At the molecular scale, the decrease in the Tgel and tgel with increasing the mass ratio of [CS]/[BSA] was attributed to the breaking down of hydrogen bonding sites in the CS molecules with increasing temperature, and thereby allowing the hydroxyl group to engage in intermolecular hydrogen bonding with the BSA polar amino acid residues. The hydrogen bonding in addition to other non-covalent forces appeared to strengthen the microstructure of the CS/BSA gel as confirmed by the dynamic frequency sweep test. The frequency sweep test also showed that the value of the storage modulus (G′) at [CS]/[BSA] = 3 was about 10 to 103 orders of magnitude larger than its value recorded for the pure BSA. Kinetically, the gelation process was well modelled by the temperature dependency of reaction rate constant as represented by the Arrhenius equation. If interpreted in terms of the energy required to attain the gel state, the addition of CS reduced the gel activation energy (Ea) to 153.90 kJ/-mol as against the original value of 268.55 kJ/mol that was observed for the BSA without CS.