| Starch phosphate (SP) is one kind of starch derivative produced fromesterification of starch and phosphate. As a kind of multifunctional additive, itcan be widely used in paper-making, textile, food industry and has greatpractical value and market prospect. Because of regular crystalline regions of thestarch, it is difficult for chemical reagent to contact with inner molecular, whichresults in low starch activity in reaction, low reaction efficiency and productswith low degree substitution (DS). So there is great interest in methods tomodify the structure in the crystalline region to improve starch reaction activity.It is also significant to widening application of starch phosphate. In this thesis,the effects of ultrasonic wave on structure and properties of cassava starch andits application in preparation of starch phosphate were investigated, by whichnew preparation technology was studied. The adsorption process of copper ionby starch phosphate and application were also discussed.(1) The ultrasonic effects on functional groups, crystal structure, granularmorphology, amylose content and thermal property of cassava starch wereinvestigated respectively by using Fourier transform infrared spectroscopy, X-ray diffractometry, scanning electron microscopy, analysis of starch-iodinecompound absorption spectrum, titration and differential scanning calorimetry.Structure analysis suggested that ultrasonic wave wouldn't destroy functionalgroups of starch, but damaged crystal structure; crystallinity decreased; reactionactivity was improved; there were dents on starch granules surface; chainsruptured and paste temperature raised.(2) The ultrasonic effects on physicochemical properties of cassava starchwere investigated by analyzing the variation of rheological characteristics,transparency, retrogradation and enzyme resistance. The results indicated thatapparent viscosity, thixotropy and shear-thinning nature of the starch pastesdecreased; starch treated by ultrasonic wave had pseudoplastic characteristicsaccording with the power law. In addition, transparency increased and enzymeresistance decreased because of ultrasonic treatment to some extent. Butlongtime ultrasonic treatment would result in decrease of transparency andincrease of enzyme resistance. Degradation of starch paste was enhanced;transparency descended significantly and paste had strong retrogradation.(3) Starch phosphate was prepared by ultrasonic pretreatment combiningwith traditional semi-dry process. Effects of ultrasonic treatment time (tu), power(P), dispersant and its concentration on DS and viscosity were investigated. Theresults indicated that starch phosphates could be obtained upon such treatmentconditions as follow: 20％ethanol was dispersant, ultrasonic power was 300 w,treatmenttime was 2.5 min, DS of starch phosphate increased by 25％ comparing with that of the products without ultrasonic pretreatment. Viscosity ofproducts decreased and varied with the variation of treatment conditions.(4) The adsorption of Cu2+ by starch phosphate and its application inrestraint of aloe browning were discussed. Single factor experiments ofadsorption indicated that starch phosphate could adsorb Cu2+, adsorptionefficiency reached 97％upon such conditions as follow: concentration of Cu2+was 507.28 mg/L, solution volume was 50 mL, 25℃, pH was 5, amount ofstarch phosphate was 2g, DS was 0.05, adsorption time was 50 min. Whentemperature was below 35℃, adsorption rate increased with temperature'selevation. Apparent activation energy was 18.167 kJ/mol.ΔG＜0 suggestedadsorption of Cu2+ by starch phosphate was a spontaneous process.ΔH＞0indicated it was an endothermal and chemistry adsorption process. According toLangmuir equation, saturating adsorption capacity was calculated, which was12.5455 mg/g. Application experiment indicated that Cu2+ intensified activity ofpolyphenoloxidase and accelerated aloe browning. Starch phosphate couldadsorb Cu2+ desorbed from polyphenoloxidase in low pH. When exogenous Cu2+existed, starch phosphate could adsorb Cu2+, interfere the combination ofpolyphenoloxidase and Cu2+, restrain polyphenoloxidase activity and delay aloebrowning.
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