Effects of carrageenan on the molecular weight and microstructure of gluten during freeze- thaw cycles storage

In this paper,the effects of freeze- thaw cycles( frozen at- 18 ℃ with cycling to 0 ℃ for 12 h and then back to- 18 ℃ per 10 days) on molecular weight and distribution,protein subunits,free sulfhydryl group and microscopic property of gluten with carrageenan were studied by the multiangle laser light scattering( MALLS) in combination with size exclusion chromatography( SEC),sodium dodecyl sulfate- polyacrylamide gel electrophoresis( SDS- PAGE) and scanning electron microscopy( SEM).The results showed that during the freeze- thaw cycles,the molecular weight of the gluten was significantly decreased,especially in 105~ 106 u,while the molecular weight of the gluten added carrageenan descreased slightly contrast with the control. The SDS- PAGE profiles revealed that there were no remarkable difference and relative mobilities of band for the gluten protein subunits.The free sulphydryl group content increased during the storage,the 4.89 μmol / g for control compared with4.13 μmol / g for the gluten added carrageenan stored for 120 days,which implying the carrageenan can offer protection to the disulfide bonds.SEM photographs showed that the network was weakened with increasing freeze- thaw cycles storage time,the pore size of the control sample was increased to 50 μm after stored for 120 days,while the gluten added carrageenan was highly uniform in size. These results indicated that the addition of carrageenan could reduce the depolymerisation caused by recrystallization and protect the structure of gluten.