Comparison of egg white protein,soy protein isolate and associated Maillard reaction products as coating- films on walnuts lipid peroxidation

The egg white protein,soy protein isolate and associated Maillard reaction products were compared as coating- films on the walnut lipid peroxidation,which was analyzed using walnuts' acid values,peroxide values,MDA contents and iodine values,DPPH radical scavenging rates. The results showed that walnuts' acid values,peroxide values and MDA contents were increased with the extension of heating time( 0 ~8d),while DPPH radical scavenging rates were decreased during heating process,but the iodine values had no obvious change. When heated at 50℃ for 8d,the acid values,peroxide values and MDA contents were higher for the uncoated walnuts than the coated walnuts,while DPPH radical scavenging rates were lower for the uncoated walnuts than the coated walnuts.There was no significant difference in acid values among four film-coated walnuts; the peroxide value of the walnuts coated by EWP film was the highest among four film- coated walnuts,while there was no significant difference among other three films; the MDA contents were lower in four film- coated walnuts than in uncoated walnuts,and inhibitive effects of MDA production were in a descending order of SPI- Xyl film > EWP- Xyl film > SPI film > EWP film.The DPPH radical scavenging rate of the walnuts coated by SPI- Xyl film was the highest,and there was no significant difference among other three films.In conclusion,the walnuts' lipid peroxidation was inhibited by four different protein films with a descending order of SPI-Xyl film > EWP-Xyl film > SPI film > EWP film.