Study On The Mechanism Of Arabinoxylan Regulating Gluten Thermal Aggregation Behavior Based On Its Structure Oriented Modification

Wheat is the main grain crop in China and the main raw material for making flour staple food.Gluten is the main component of dough with viscoelasticity,which directly affects the processing quality of dough.With the development of society and economy and the improvement of people’s living standard,the market space of functional cereal products with much dietary fiber is expanding.Arabinoxylan(AX)is the main dietary fiber in wheat bran,which can regulate blood cholesterol,reduce cardiovascular disease and diabetes.At the same time,AX can act on gluten and affect the processing quality of flour products.In the process of dough ripening,glutenin and gliadin in gluten will be crosslinked and shaped through heating aggregation to form a framework structure,which ultimately determines the edible quality.However,the structure-activity relationship of AX regulating the aggregation behavior of gluten in the heating process remains to be clarified,.The mechanism of AX induced gluten aggregation is unclear,which hinders the development of AX as a flour conditioner..In this paper,we first modified AX with α-L-arabinofuranosidase(AXH-m,AXH-d3)to obtain four kinds of AX with disubstituted or monosubstituted side chains,which are LM-AX,LD-AX,HM-AX and HD-AX,respectively.On this basis,the aggregation mechanism of AX with different structure on wheat gluten during heating process was studied from the aspects of macro,micro and molecular structure,so as to provide a theoretical basis for regulating the quality of gluten and improving the quality of flour products.The specific research contents and conclusions are as follows:The effects of enzyme modified AX on the rheological and thermal properties of gluten were studied by rheometer,thermogravimetric analyzer and differential scanning calorimeter.The results showed that LM-AX and HM-AX could improve the elastic and viscous modulus of gluten,and the effect was significantly enhanced.After removing Araf from the monosubstituted C-3 side chain,the flexibility of the molecular chain is reduced,and it is not easy for AXto combine and interact with gluten.At the same time,AX also increases the hydrophobicity of gluten,makes the structure of gluten more loose and extended,reduces the aggregation degree of protein,and reduces the thermal stability of gluten.Laser confocal microscope,atomic force microscope,particle size analyzer and capillary viscometer were used to study the effects of enzyme directed modification on the microstructure,morphology,particle size distribution and intrinsic viscosity of gluten.LM-and HM-AX increased the gluten height and the median particle size,especially HM-AX increased the Huggins constant to the peak,because the conformation of LMand HM-AX with the C-3 Araf group removed was denser.Under the high temperature,the ability of forming hydrogen bond with gluten was enhanced,which promoted the aggregation of protein molecules.The effects of AX on molecular weight,subunits,SH,noncovalent forces,secondary structure and hydrophobicity of glutenin were studied by molecular exclusion chromatography,reversed phase exclusion chromatography and fourier transform infrared spectrometer.The results showed that the single substitution distribution pattern of Araf group in AX side chain could significantly promote the aggregation of glutenin and gliadin in glutenin after 90℃.After structural modification,AX mainly affected the degree of α-alcohol soluble protein and γ-gliadin participating in aggregation,and the double substitution distribution mode of side chain Araf group had more significant effect on α-gliadin.LD-and HD-AX can reduce SH content and affect the secondary structure of gluten protein more than LM-and HM-AX.At 70℃,the hydrophobicity of glutenin was reduced by structure modified AX.The single and double substitution modes of Araf group at C-3 position of AX side chain have similar influence.After the enzyme modification,AX reduced the number of side chain groups and reduced themolecular asymmetry.It combined with glutenin molecules to form complex spatial conformation,which affected the aggregation of subunits in glutenin,and promoted the cross-linking between glutenin and glutenin,glutenin and gliadin.