Effect of Soy Protein Isolate on Pasting, Rheological, and Textural Attributes of Potato Starch

The effects of different concentrations of soy protein isolate (SPI) on the functional, rheological, pasting, and structural properties of potato starch (PS) are investigated. The water and oil absorption capacity (OAC) of PS-SPI mix increased significantly with the addition of SPI. Gel strength, peak, final, breakdown, and setback viscosity of PS decreases, whereas the pasting temperature increases with an increase in SPI fraction. Both the Herschel–Bulkley and power law model are found to equally fit in steady state rheology. The PS-SPI blend exhibits pseudoplastic behavior. The addition of SPI decreases the storage (G′) and loss modulus (G″). SPI also lowers the flow stress values in the amplitude sweep test. Frequency sweep confirms the formation of weak gel formation in PS-SPI blend by exhibiting a lower value of G′ and G″ than the pure starch. The microstructure of composite gel appears less dense with greater pore size than starch gel. The hardness of the SPI-PS blend gel decreases from 6.76 to 0.85 N when the SPI content is increased from 0% to 50%. Fourier transform infrared (FTIR) confirms that no chemical groups are formed or destroyed during the composite gel-making process.