Effect Of Polydextrose On The Stability Of Wheat Gluten Protein Under Freeze-Thaw Cycle

Wheat flour is mainly composed of starch and wheat gluten,and gluten determines the main quality of the pasta.In the quick-frozen pasta,the moisture migration of gluten during the process of freezing,the loosening of the spatial network structure and the denaturation of the secondary mechanism affect the quality of the product and restrict the development of the frozen pasta.The gluten-hydrocolloid combination can effectively deteriorate the Wheat Gluten Proteinfrozen,improve product quality and extend the shelf life of the food.There were fewer research on water-soluble dietary fiber used as a new antifreeze added to gluten to study its antifreeze mechanism.In this paper,polydextrose was added to gluten and glutenin which is main component of gluten to investigate the effects of polydextrose on the water molecules state,thermal properties and rheological properties in gluten and glutenin secondary structures at room temperature and freeze-thaw conditions.The effects of polydextrose on the microstructure and macroscopic properties of gluten were studied from microscopic and macroscopic levels,respectively.The main conclusions are as follows:The effects of polydextrose on the functional properties of wheat gluten at room temperature were investigated by using the Nuclear Magnetic Resonance,rotary rheometer,Fourier infrared and scanning electron microscopy.The results showed that the water holding rate of gluten increased with the addition of polydextrose.The bound water content reached the maximum value of 17.05%when the concentration of polydextrose was 6%.The addition of polydextrose increased Elastic modulus G’ and viscous modulus G".The minimum tanδ value and the best degree of polymerization were observed when the concentration of polydextrose was 6%.Adding polydextrose decreased β-sheet,and α-helix reached the maximum value of 15.66%when the addition of polydextrose was 6%.The microstructure showed that the wheat gluten with 6%polydextrose has smaller pore size and more uniform network structure.The addition of polydextrose at room temperature can improve the microstructure of gluten and enhance its functional properties.By measuring the thermal hysteresis of polydextrose,it was found that polydextrose had a good antifreeze mechanism.The effects of polydextrose on moisture migration,viscoelasticity,thermodynamic properties,protein secondary structure and microstructure of gluten under freeze-thaw conditions were studied.It was found that as the number of freeze-thaw cycles increased,the free water content of gluten,the elastic modulus G’ and the viscous modulus G" gradually decreased.Adding polydextrose restricted the moisture migration of gluten protein,slowed down the viscoelasticity of the Wheat Gluten Proteinand enhanced the thermodynamic properties of gluten.As the number of freeze-thaw cycles increased,α-helix decreased and β-turn increased.The addition of polydextrose increased α-helix and weakened the effect of freeze-thaw on the secondary structure of gluten.The three-dimensional network structure of gluten was destroyed by freeze-thaw.With the increase of freeze-thaw cycles,the gluten network structure was broken and the pore size became larger.The more uniform and denser pores were observed after adding polydextrose.The results indicated that the addition of polydextrose effectively reduced the growth and recrystallization of ice crystals,weakened the deterioration of gluten because of freezethaw cycles and significantly enhanced the freeze-thaw stability of gluten.The effects of polydextrose on the freeze-thaw stability of glutenin which is main component of gluten were investigated by using low magnetic field NMR,dynamic rheometer,differential scanning calorimetry,Fourier infrared and scanning electron microscopy.Adding polydextrose reduced the loss of bound water content of glutenin in the freeze-thaw cycle;enhanced the number and force of β-sheet,slowed the depolymerization rate of glutenin and attenuated temperature fluctuations against the secondary structure of glutenin.At the same time,as the number of freeze-thaw cycles increased,the fibrous spatial network structure of glutenin became broken or even agglomerated.The addition of polydextrose kept its network structure in good continuity,which improved the thermodynamic properties and elasticity of glutenin to a certain degree.