Impact of xanthan gum on gluten microstructure and bread quality during the freeze-thaw storage

Xanthan gum (XG) is commonly used as a hydrocolloid in frozen dough to improve the texture and the sense quality of the products. The effects of XG on the molecular weight, secondary structure, microstructure of gluten and bread quality during freeze-thaw storage were studied. As results showed, XG and gluten formed more compact complexs through electrostatic interactions, which relieved the destruction of side chain molecules for gluten. XG protected the molecular weight of gluten proteins from 2 x 10(6) Da-10(8) Da. FTIR showed that XG-gluten mixtures had more alpha-helices (28.98%) and less intermolecular beta-sheets (9.45%) compared with gluten. The secondary structure of XG-gluten remains unchanged under freeze-thaw treatment from 0 to 60 days. However, when the time reached 120 days, there was a decrease in alpha-helices (11.85%) and fl-turns (6.28%) accompanied an increase by beta-sheets (19.13%). CLSM revealed that XG gradually migrated to the centre with moisture after freeze-thaw storage, thereby protecting the gluten network. So the bread, prepared from XG-gluten mixtures, possessed superior colour, volume and visible pore proportion than bread without XG. Overall, the freeze-thaw stability of the gluten was enhance by XG under freeze-thaw treatment from 0 to 90 days.