Study On The Mechanism Of Quality Improvement In Frozen Dough And Its Bread With Magnetic Field

Frozen dough enables the manufacturing process of bread standardization and convenience.However,long-term frozen storage will inevitably deteriorate the quality of dough,and the improvement methods proposed have the limits such as complicated process,hidden safety hazards of using food additives and high cost.While the magnetic field freezing,as a low-cost and free-polluted method,has been proven to delay the quality deterioration of fruits,vegetables and meats.Therefore,this research explored the effect of static magnetic field(2m T)on the frozen dough.One the one hand,the quality of dough and bread under a magnetic field was investigate,and the improvement mechanisms were examined from the behaviors of three major components of dough(water,gluten and yeast).On the other hand,the different effects of magnetic field addition to freezing and frozen storage were studied.The main research conclusions were as follows:(1)The application of magnetic field during freezing process inhibited the formation of ice crystals in the freezing stage(the freezing point is reduced from-3.7°C to-4.4°C,and the phase transition is shortened from 28 min to 21 min)and ice crystallization in the storage stage(compared with the traditional frozen storage,freezable water content in the 60-day was reduced by 1.78%),which in turn affected the gluten network and yeast of dough in a short-term frozen storage(30d).Compared with traditional frozen storage,on the one hand,the magnetic field only significantly reduced the free SH content and delay the increase ofα-helix content during the frozen storage of 30-day,and has little effect on the glutenin macropolymer(GMP)depolymerization and the microstructure of gluten.On the other hand,magnetic field only significantly increased the yeast survival rate and reduce the GSH content in the 30-day frozen storage.Therefore,magnetic field showed little effect on the gassing capacity and gas-holding capacity of frozen dough(after 60-day of frozen storage,the air production and increased proofing volume of dough with magnetic field only numerically increased than that of the traditional treatment).Finally,magnetic field only improve the specific volume of bread product(increased from 2.73 cm~3/g to 2.84 cm~3/g after 60 days).(2)The application of magnetic field throughout the whole frozen storage also inhibited the formation of ice crystals(same as above)and ice recrystallization(compared with the traditional treatment,the freezable water content in the 60-day frozen storage was reduced by5.47%),which influenced gluten network and yeast of dough in a long term(60d).Compared with traditional treatment,on the one hand,magnetic field slowed down the trends of SS bonds breaking,GMP depolymerization andα-helix content increasing(after 60-day frozen storage,the content of free SH content andα-helix were decreased from 1.256μmol/g and 29.19%to1.201μmol/g and 25.65%,respectively,and the content of GMP increased from 11.49%to14.71%),and maintained the integrity of gluten network and its cross-linking with starch.On the other hand,magnetic field inhibited the inactivation of yeast(the yeast survival rate increased from 23.20%of traditional frozen treatment to 51.00%in the 60-day frozen storage)and the release of GSH in a long term.Therefore,magnetic field has a long-term improvement effect on the gassing capacity and gas-holding capacity of frozen dough(after 60-day frozen storage,the air production and increased proofing volume of dough was significantly increased from 99 cm~3 and 78.00 cm~3 in traditional frozen treatment to 141.5 cm~3 and 104.00 cm~3,respectively).Finally,in terms of bread quality,the uniform pore structure,original column,soft crumb and skin of color were better preserved.(3)By comparison,it is found that the magnetic field only applied in storage process,would inhibit ice recrystallization.Then it prolonged the positive effect on the gluten protein and yeast when applying magnetic field only during freeing.Therefore,on the basis of the applying magnetic field in the freezing process,the application of magnetic field in the storage process can further improve the gassing capacity and gas-holding capacity of frozen dough and the bread product quality.