| Starch is an important component of wheat flour and a natural macromolecular compound.Natural wheat starch is not easy to react with other substances because of its dense crystalline area.In addition,the grain size of wheat flour is an important factor restricting the processing quality of wheat flour.As the main component of wheat flour and the filling material in noodles,the structure and physical and chemical properties of starch have an important effect on the quality of flour and noodles.In this study,a planetary ball-milling was used to treat wheat starch at a speed of 200r/min.After 30 min,60 min,120 min and 180 min,five wheat starches with different degrees of treatment were obtained.The effects of ball-milling time on the structural properties and physicochemical properties of starch were studied.The effect of the change of starch structure and physicochemical properties on the quality of the recombination powder and noodles was studied.(1)Using a laser particle size analyzer,scanning electron microscope(SEM),polarizing microscope(PLM),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FTIR)to investigate the particle size distribution,apparent morphology,polarization cross,crystalline structure and molecular structure of wheat starch,respectively.The results showed that with the prolongation of milling time,the grain size of starch decreased significantly and eventually tended to be stable.Polarized light microscopy and X-ray diffraction analysis showed that the polarized cross of starch after ball milling gradually disappeared,the diffraction peak changed from sharp peak diffraction to dispersion peak diffraction,and the crystallinity decreased from 21.24% to 17.71%,which indicated that the ball-milling treatment caused serious damage to the crystalline structure of starch.Fourier transform infrared analysis showed that no new groups were formed in the starch molecules after ball-milling,but the ordered structure of starch particles was destroyed and the disordered structure increased obviously with the extension of ball-milling time.(2)The damaged starch content,solubility and swelling power,transparency,gelatinization,thermal properties and gel properties of wheat starch were determined.The results showed that the content of damaged starch increased significantly from 26.55% to38.05% after ball-milling 180 min.The solubility,swelling power and transparency of starch were significantly increased because the morphology and crystalline structure of starch were destroyed by ball-milling.After ball-milling,starch is easier to gelatinize,and the gelatinization enthalpy ?H is significantly reduced.The results of gelatinization showed that the peak viscosity,trough viscosity and final viscosity of starch decreased significantly,and the setback value also decreased.With the prolongation of milling time,the hardness,adhesiveness,resilience,springiness and chewiness of starch gel decreased significantly.In conclusion,the physicochemical properties of starch were significantly changed due to the destruction of starch structure by ball-milling.(3)The particle size distribution,color,solvent retention,gelatinization and thermal properties of the recombination powder were analyzed.The results showed that the grain size of the reconstituted wheat flour was significantly lower than that of the original flour,and the grain size of the reconstituted wheat flour showed a bimodal distribution.The reconstituted wheat flour has a whiter and brighter color.Compared with the original flour,the solvent retention of sodium carbonate,sucrose,distilled water and lactic acid increased significantly,indicating that the contents of damaged starch and pentosan in the recombination wheat flour obtained by ball-milling were increased.The variation trend of gelatinization and thermal properties of the recombinant powder was consistent with that of starch.Moreover,compared with the original flour,the gelatinization characteristic values of peak viscosity,trough viscosity and final viscosity of the recombinant flour were significantly reduced,and the setback value was also significantly reduced.The gelatinization enthalpy(?H)for phase transition of the recombinant wheat flour was also significantly reduced.(4)The color,cooking quality,texture and sensory quality of the noodles were analyzed.The results showed that the brightness of the noodles increased significantly with the extension of ball-milling time.The cooking loss rate and water absorption of dry matter of noodles were significantly increased.The texture analysis of the noodles showed that the hardness and chewiness of the noodles increased at first and then decreased with the extension of ball-milling time,and the adhesion of the noodles decreased significantly.Sensory evaluation showed that the highest score was obtained after moderate ball-milling treatment of starch(30 min).In a word,in this paper,the grain structure,surface morphology,crystal structure and molecular structure of wheat starch were destroyed by ball-milling,and the degree of ordering was decreased and the degree of disordering was increased.The change of structure leads to the change of physicochemical properties.With the increase of ball-milling time,damaged starch content,solubility,expansion potential and transparency increased significantly,while,peak viscosity,low viscosity,disintegration value and recovery value decreased significantly,and gelatinization enthalpy also decreased significantly.Correspondently,after recombination of ball-milling starch and gluten powder,the trend of gelatinization properties and gelatinization enthalpy of the recombination powder were consistent with that of starch.The particle size of recombinant powder was significantly reduced.After making the reconstituted noodles,it was found that the reconstituted noodles with moderate ball-milling starch(30 min)had the highest score. |
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