Preparation And Performance Research Of Debranching Cross-linked Potato Starch

The debranching potato starch (DPS) and debranching cross-linked potato starch (DCPS)were prepared by using potato starch as the raw materials, pullulanase as the hydrolysisreagent, phosphorous oxychloride as a cross-linking agent and sodium hydroxide as thecatalyst. Response surface methodology based on the Box-Behnken design was employed forthe statistical optimization of the technological parameters for the hydrolysis of potato starchand cross-linking of DPS. Furthermore, the property of DPS and DCPS were studied. Theeffect of factors such as the debranching temperature, debranching time, pH and amount ofpullulanase on the debranching degree of DPS and the influence of reaction temperature,reaction time, pH and phosphorus oxychloride dosage on the substitution degree of DCPSwere investigated, respectively. The debranching degree of DPS was determined by DNSmethod and the substitution degree of DCPS was determined by phosphomolybdenum bluespectrophotometric method. At the same time, the structure, thermal property and particleshape of the DPS and DCPS were characterized, analysed and observed by the infraredspectrometer, thermogravimetric analyzer, differential scanning calorimeter, X-ray diffractionand polarizing microscope.The results showed that the optimal technological conditions for preparing the DPS were:debranching temperature53℃, debranching time2h, pH4.2and amount of pullulanase58U/g (dry potato starch), respectively. The optimal technological conditions for preparing theDCPS were: reaction temperature35℃, reaction time100min, pH10.5and phosphorusoxychloride dosage1%(mass percentage ratio of phosphorus oxychloride to the drydebranching potato starch), respectively.After potato starch was modified by the pullulanase and cross-linking, its acid resistance,alkali resistance and retrogradation enhanced, its transparency and blue value increased, but itsfreeze-thaw stability and expansion capability decreased. After DPS was crosslinked, however,the retrogradation was weakened.The peak of DSC curves of potato starch, debranching potato starch and debranchingcross-linked potato starch were endothermic peaks. Compared with potato starch, the initialdecomposition temperature of debranching potato starch and debranching cross-linked potato starch was reduced, but the termination decomposition temperature increased. The order of thethermal stability from strong to weak was as follows: debranching cross-linked potato starch,debranching potato starch, potato starch. The crystal structure of potato starch belonged to aB-type. After potato starch was debranched by the pullulanase, its crystal structure wastransformed into a A-type. The polarization cross of potato starch granules was distinctlyobserved. However, the polarization crosses of debranching potato starch and debranchingcross-linked potato starch were disappeared, and the particle shape and size were changed.