Study On The Preparation And Application Of Sweet Potato Slowly Digestible Starch

Slowly digestible starch(SDS)is provided with a lot of special physiological functions.It can slow down the rate of digestion and absorption,maintain postprandial glucostasis,release energy persistently,prevent and cure chronic disease associated with diet.Preparation of SDS by using heat-moisture and organic acid complex methods is safe and reliable,and the content of SDS is high.The sweet potato starch was the raw material in this paper.We used heat-moisture and organic acid complex methods to improve the content of slowly digestible starch.And the physicochemical properties and applications of the sweet potato slowly digestible starch were researched.The main research contents and results are as follows:1.Based on single factor experiments,the preparation conditions of sweet potato slowly digestible starch were optimized by using response surface methodology.And the key factors were selected.A mathematical regression model was established for the content of sweet potato slowly digestible starch at different levels of three corresponding factors,that were percentage of moisture content,lauric acid reaction time and lauric acid addition.The optimal preparatory conditions were obtained as follows: moisture content of 47 %,reaction temperature of 100 ?,lauric acid addition of 25 % and heating treatment time of 4 h.Under the optimized conditions,the content of sweet potato slowly digestible starch was 13.03 % and increased by 8.85% compared to that of untreated sweet potato starch.2.The physicochemical properties of the sweet potato slowly digestible starch were studied.The conclusions were listed as follows.Compared with the ordinary sweet potato starch,the pasting temperature of heat-moisture and organic acid treated starch increased.The peak viscosity,trough,final viscosity,breakdown and setback of treated starch all decreased.The surface of ordinary sweet potato starch granules was complete,its shape were spherical or polyhedral with smooth surface.The surface of heat-moisture and organic acid treated starch granules was not complete,and there were signs of damage.There was a phenomenon that the starch granules were closely integrated with each other.X-ray diffraction results showed that the crystalline structure of sweet potato starch was C type,and crystalline of heat-moisture and organic acid treated starch was V+B type.The peak values and enthalpy values of SDS were different with normal starches'.It indicated the formation of starch-lipid complexes that cause the slow digestion.3.The application of sweet potato slowly digestible starch in toughness biscuits was studied.The results were indicated as follows.With the increase of slowly digestible starch content,the moisture content increased relative to control biscuits,the ash content changed little under the same conditions.The hardness of biscuit with different amounts of SDS was compared.We found that the hardness of adding different SDS levels decreased compared with the control group.The hardness of 15% SDS biscuit was minimum.Each group of biscuit's sensory analysis score was not significantly different,but the scores of the appearance,color,taste and total scores were higher than control group.The score of 15% SDS group is the highest.