Effect Of Ultrasound,Enzyme And Annealing On The Structure And Physicochemical Properties Of Sweet Potato Starch

Physical modification of starch has attacted much attention recently for its invironmental friendness and safety.Amylase plays a more and more important role in food industry.The effects of annealing treatment(AN),ultrasonic treatment(UL),dual modification of ultrasonic and annealing(UL-AN),dual modification of enzyme and annealing(EN-AN),three modification of enzyme,ultrasonic and annealing(UL-EN-AN)on properties of sweet potato starch was investigated.The main results obtained were as follows:Annealing effects on the structure and properties of sweet potato starch depended on annealing time and annealing temperture.In this work,annealing did not change the granule morphology and crystallie pattern at the proper temperature,however a relatively high annealing temperature(45?,50?)caused severe deformation or breakage of starch granules.There was an increase in the relative crystallinity,short-range molecular order and gelatinization enthalpy(?H)after annealing treatment.Annealing obviously increased the To,Tp and Tc,especially for To.Significant decreases was found in Tc-To,peak viscosity(PV),breakdown(BD)and setback(SB)of annealing starch.Such as,the peak viscosity,breakdown and setback decreased 27.07%,95.16%and 27.59%compared with the native starches after the annealing treatment of 5 days.Annealed starches had a better resistant to high temperuture and strong mechanical shearing force and lower retrogradation than native starches.Anneaing also increased the particle size,transparency and decreased swelling power.Ultrasonic treatment deceased the relative crystallinity,short-range molecular order and ?H.And along wih the incease of the power of ultrasound,the properties were changed more remarkably.Ultrasonic treatment also deceased transparency.However,ultrasonic treatment increased the peak viscosity,breakdown,setback,swelling power.The relative crystallinity,short-range molecular order,?H and transparency were increased after UL-AN teratment and higher than AN and UL trearment,this show that dual modification of ultrasonic and annealing will make the starch crystal structure more perfect.The PV,BD and SB were ranked as:UL>AN-UL>AN.The oil absorption rate of EN-AN starch and UL-EN-ANstarch was higher than native starch,and the more enzyme content,the more increase.Its show that enzymes can form pores on the surface of starch granules,and ultrasonic treatment can promote the action of enzymes to make the cavities in the granules larger and deeper.The relative crystallinity,short-range molecular order and ?H of diffirent modified starch were ranked as:AN>Native>EN-AN>UL-EN-AN.The UL-EN-AN starch had the smallest peak viscosity,breakdown,setback,swelling power and the largest transparency.