Microstructure Of Gluten Research Articles

Effects of Ultrasound Pretreatment on the Enzymolysis and Structural Characterization of Wheat Gluten

Ultrasound pretreatment of protein could improve the angiotensin-I converting enzyme (ACE) inhibitory activity of hydrolysates and by alerting the structure of enzyme substrates. In this research the effects on ACE inhibitory activity and enzymolysis efficiency were explored under the optimum counter flow ultrasound (CFU) pretreatment conditions which obtained from our previous studies. The mechanism was studied by microstructure, nano-mechanical properties and secondary structures of wheat gluten (WG), which measured by scanning electron microscopy (SEM), atomic force microscopy (AFM), and flourier transform infrared spectrum (FTIR). The results showed that the CFU pretreatment resulted in significantly (P < 0.05) higher value compared with control, the ACE inhibitory activity was increased by 29.8 % and the value of IC50 was decreased by 36.92 %. CFU pretreatment increased the initial reaction rate by 9.58–20.27 % at a substrate concentration of 10–50 g/L, the KA was increased by 2.90 % and KM was decreased by 15.83 % compared to control. The microstructure revealed that the meshwork structure of WG was loosened and the surface roughness values of R a and R q were increased by CFU pretreatment. The nano-mechanical analyses showed that CFU pretreatment redistributed the adhesion map and decreased the stiffness. The secondary structures were less ordered by CFU pretreatment. Intermolecular β-sheet of protein aggregation and random coil were increased, Intramolecular β-sheet, α-helix and β-turn were decreased. It was concluded that CFU pretreatment can remarkably improve the ACE inhibitory activity of hydrolysate and enzymolysis efficiency of WG confirmed by the changes of microstructure, nano-mechanical properties, and secondary structures.

Effects of Gliadin/Glutenin and HMW‐GS/LMW‐GS Ratio on Dough Rheological Properties and Bread‐Making Potential of Wheat Varieties

AbstractThe gliadin/glutenin ratio of 15 diverse wheat varieties ranged from 0.75 to 1.16, whereas the high molecular weight glutenin subunits (HMW‐GS) to low molecular weight glutenin subunits (LMW‐GS) ratio of these varieties ranged from 0.31 to 0.93. Gliadin/glutenin ratio showed a significant negative relationship with specific loaf volume (r = −0.73), dough development time (DDT; r = −0.73), dough stability (r = −0.79) and positive associations with LMW quantity (r = 0.72). Mixolab classified the wheat varieties into two groups on the basis of HMW‐GS located at Glu‐A1 and Glu‐D1. Wheat varieties HI 977 and DBW 16 with subunits 2* and 5 +10 at Glu‐A1 and Glu‐D1, respectively, exhibited the characteristics of “extra strong” doughs with longer DDT of 8.3 and 7.2 min, and higher dough stability values of 9.1 and 8.6 min, respectively. Wheat varieties C 306, HW 2004 with null allele at Glu‐A1 and 2 + 12 at Glu‐D1, in contrast, were weak as they developed quickly, with low dough stability (≤4 min).Practical ApplicationsBread has been one of the principal forms of food for man from the earliest times. Bread quality is determined by the composition and molecular structure of gluten which in turn controls the interactions of gluten subfractions during processing. Rheological properties, microstructure of gluten, gliadin/glutenin ratio and HMW‐GS/LMW‐GS ratio have been found to be associated with bread‐making quality of wheat varieties. The research implications may be utilized both by industry personnel as well as researchers to assess the bread‐making quality of wheat varieties.

Rheology and microstructure of gluten and soya-based o/w emulsions

Highly concentrated oil-in-water (o/w) emulsion stabilised by means of gluten and soya protein isolate (SPI) at low pH have been characterized by means of linear dynamic viscoelasticity and droplet size distribution analysis (DSD). The microstructure of these emulsions has been characterized at a colloidal level by using confocal laser scanning microscopy (CLSM) and light microscopy (LM). These emulsions always exhibited a behaviour characteristic of highly flocculated emulsions with a mechanical spectrum showing a well-developed plateau region. DSD results generally showed log normal bimodal profiles. Microstructure images revealed occurrence of a close packing of droplets with a broad distribution of sizes participating in the formation of a three dimensional flocculated network. The Mason model of elasticity of compressed emulsions has been used to correlate viscoelastic and microstructural parameters giving adequate fitting but underestimating the elastic properties obtained for the highest concentration of gluten. These deviations may be explained in terms of an enhancement of the elastic network formed in the aqueous phase in which the glutenin fraction must play an important role.

In situ observation of the freezing process in wheat dough by confocal laser scanning microscopy (CLSM): Formation of ice and changes in the gluten network

Freezing of bread dough is widely applied in food industry. However, freezing impairs the baking performance of dough, which is largely attributed to structural changes as induced by ice formation. The aim of the present investigation was to image ice formation during freezing of dough and to assess the structural changes in the gluten network. A confocal laser scanning microscope (CLSM) equipped with a freezing stage was used to follow ice formation in the reflection and transmission (bright field) mode. Wheat dough with air inclusions served as a model for fermented dough. The gas pores and the ice crystals could be imaged by confocal laser reflection. Ice formation was initiated at the gas pore interface, where large ice crystals were formed during a freezing time of 4 h at −15 °C. The freezing of gluten samples stained with rhodamin was followed in the fluorescence mode. The cryoconcentration of gluten could be observed, but no irreversible changes in the microstructure of gluten were detected upon thawing. It is concluded that the gas pore interfaces in dough are preferential sites for ice nucleation, favouring the growth of ice crystals in these regions and by this a freeze induced redistribution of water in dough.