Study On The Comprehensive Utilization Of Purple Sweet Potato Residue

In the present thesis，the purple sweet potato residue（PSPR）after beingextracted pigment，as the raw material， was studied for its comprehensiveutilization．The main contents include：the ultrasonic extraction of pigment fromPSPR，the preparation of starch from PSPR，the physicochemical properties ofpurple sweet potato starch（PSPS），ordinary PSPR powder and super-fine PSPRpowder．（1）Study on the ultrasonic extraction of pigment from PSPROn the basis of single factor experiment，the optimum ultrasonic extractionconditions of pigment from PSPR were determined by orthogonal experiment．Theresults were：citric acid concentration3%，ultrasonic temperature60℃，thesolid-liquid ratio1g:40ml and ultrasonic time25minutes．The extraction amount ofpigment was88.391mg／100g in this condition．（2）Study on the preparation of starch from PSPRThe extracting process：PSPR→Drying、crushing→Soaking（solid-liquid ratio1g:10ml，temperature30℃and time2.5h）→Screening（80mesh and200mesh）→Alkaline cleaning（pH value10，stirring time20minutes）→Centrifuging（3000r／min,10min）→Ajusting pH（pH＝6）→Centrifuging（3000r／min,10min）→Drying、crushing（100mesh）→Product．In this condition，starch extraction rate could reach85.09%，the purity ofstarch could be up to93.21%．（3）Study on the physicochemical properties of PSPS，ordinary PSPR powderand super-fine PSPR powderCompared with potato starch，sweet potato starch（SPS），corn starch，thephysicochemical properties of PSPS were as follows． PSPS contains moreamylase．Its particle size and shape are similar to SPS，mostly round andpolygonal，and80%of particles are distributed between7.47μm and33.54μm．The PSPS paste has less transparency，higher sedimentation capacity，worse freeze-thawstability，higher solubility and lower swelling degree．Among the four kinds ofstarches， PSPS has the highest gelatinization temperature and the lowestgelatinization enthalpy，while the thermal stability and the retrogradation capacityare moderate．Its gelling speed is slower and the hardness of PSPS gel is thestrongest while the elasticity is the worst．On the contrast of physicochemical properties of PSPS，ordinary PSPR powderand super-fine PSPR powder，the results were as follows．Among three purple sweetpotato samples，PSPS has the highest transparency， freeze-thaw stability，gelatinization temperature and gelatinization enthalpy，the lowest sedimentationcapacity，the worst thermal stability and is the easiest to retrogradate，the slowestto gel．Its gel has the strongest hardness and the worst elasticity．Super-fine PSPRpowder particle is smaller than the others．Its paste has the lowest transparency，freeze-thaw stability，gelatinization temperature and gelatinization enthalpy，thehighest sedimentation capacity，thermal stability，and is the most difficult toretrogradate，the fastest to gel．Its gel has the best elasticity．When the temperatureis lower，the solubility and swelling degree of the two PSPR powders are higherthan PSPS，while the trend is opposite when the temperature is higher．...