Phosphorylation Of Soy Protein Isolate And Research On Functional Properties

As one of the main resource of proteins for human being, soy protein has widely applied foreground in food processing industry. To enlarge the application of soy protein isolate (SPI), phosphorylation of SPI with sodium tripoly phosphate (STP) was researched.(1) The reacting equation was y=85.456348-40.791676x₁+ 22.255394x₂ -6.324675x₄ +10.421126x₁² -15.751875 x₁x₂+11.270272x₂² -10.946875 x₂x₃ +8.609375 x₃x₄. The concentrations of SPI and STP had great influence on degree of phosphorylation (p<0.0001 or p=0.0004).(2) The effects of pH and concentration of SPI and NaCl on functional properties of SPI and P-SPI such as aqueous solubility, emulsification properties, foaming properties and viscosity were researched. The results showed that functional properties of phosphorylated soy protein isolate (P-SPI) changed in different degrees. The aqueous solubility of P-SPI when pH was between 2 and 5.5 was improved. The emulsification activity and foaming properties were also increased while the viscosity was minished. It was very favorable for these changes to develop the use of SPI on food industry.(3) The best hydrolyzing condition was determined based on the scavenging percentage of superoxide anion with chemiluminescence. The result showed that the antioxidation activity of hydrolysate from P-SPI was not weakened.(4) The SPI after phosphorylation did not change obviously according to PAGE. But the infrared absorption spectroscopy and stability of P-SPI on different pHs showed that both the hydroxyl group andε- NH₂ of SPI reacted with STP. Circular dichroism atlas proved the structure of P-SPI more compact.