Effects Of Branching Enzyme On The Rheological Properties Of Dough And The Physicochemical Properties Of Noodles

To obtain wheat noodles with slow digestibility and low retrogradation properties.In this paper,with different concentrations of BlBE（120 U/g flour,240 U/g flour,480U/g flour）were added to the processing of wheat noodles,BlBE was obtained to explore their effects on the rheological characteristics of wheat dough and the physicochemical properties of wheat noodles,which provided a theoretical reference for production of other wheat flour products with slow digestibility and low retrogradation characteristics in the future.The results are as follows:1.The glg B gene derived from Bifidobacterium longum with the p UBRT-R2 vector and expresses the recombinant plasmid p UBRTAMY-BlBE in Bacillus subtilis WB 600.The results showed that the specific activity of the extract BlBE was 3.5 U/mg,and the specific activity of the purified enzyme BlBE was 16.6 U/mg.The molecular weight of BlBE was 86.1 KDa.2.When the enzyme was added to flour at room temperature,resulting in changes in the rheological characteristics of dough and the texture characteristics of noodles.The storage modulus and loss modulus of the BlBE-modified wheat dough decreased,along with increased pseudo-plasticity.The BlBE-modified noodles’hardness,gumminess and chewiness decreased by 12.1%～45.8%,9.7%～40.4%and 16.0%～42.4%,respectively,but both resilience and cohesiveness increased by 4.0%～14.8%and 1.8%～9.0%,respectively.Pearson analysis revealed a correlation between the noodles’textural parameters and the doughs’power law equation parameters.The results showed that the rheological parameters(K_PLG’and K_PLG")are positively correlated with the hardness,gumminess,and chewiness,and their correlation values varied between 0.89 and 0.95.In addition,the K_PLG’and K_PLG"are positively correlated with the cohesiveness and resilience of the noodles,their correlation values varied between-0.87 and-0.90.3.BlBE modified noodles were measured in vitro starch digestion,retrogradation enthalpy,relative crystallinity,chain length distribution and molecular weight with method of Englyst and the instrument of differential scanning calorimetry（DSC）,x-ray diffraction（XRD）,fourier transform infrared spectroscopy（FT-IR）,high performance anion exclusion chromatography（HPAEC）and high performance size exclusion chromatography（HPSEC）.With the increasing concentrations of BlBE,the amylopectin content of modified wheat noodles increased significantly from 62.19%to 63.71%,and the amylopectin content decreased significantly from 13.28%to 11.30%（P<0.05）.With BlBE modified with a concentration of 480 U/g flour,the content of rapidly digestible starch in wheat noodles decreased significantly by 8.6%.Meanwhile,the content of slowly digestible starch in wheat noodles increased significantly by 12.6%.With the increase of the concentration of BlBE,the starch structure of wheat noodles became more and more disordered,and the relative crystallinity decreased from 33.59%to 10.51%.The retrogradation enthalpy of starch in wheat noodles modified by BlBE decreased significantly from 3.44 J/g to 0.63 J/g.Compared with that of the control noodles,the chain length of starch DP（<6）increased significantly from 3.49%to10.31%,the chain length of DP（6-12）increased significantly from 20.17%to 22.88%,the chain length of DP（13-24）decreased from 42.52%to 36.26%,and the proportion of DP（25-36）decreased from 18.25%to 16.62%.The chain length of DP（>36）decreased from 15.60%to 14.15%.The molecular weight（Mw）also decreased from 2.15×10⁷g/mol to 1.11×10⁷g/mol.The Rz decreased from 129.2 nm to 114.9 nm,the volume of rotation（Svg）increased from 0.31 cm³/g to 0.35 cm³/g,and the molecular density（ρ）decreased from 8.27 g/mol/nm to 7.34 g/mol/nm.