| V-type granular starch(VGS)has a unique V-type single helical structure,can be rapidly swelled into paste in cold-water.VGS modified by ethanol-aqueous heat treatment has complete granular morphology and high crystallinity,which is a potential excellent microcapsule carrier.However,the current research on VGS focuses on the cold-water solubility,with little reference to its formation mechanism,paste properties and loading capacity.Therefore,firstly the formation mechanism of VGS in ethanol-aqueous system was studied,the preparation conditions of VGS in three ethanol concentrations(50%,60% and 70% ethanol)were optimized,and the physicochemical properties of the three optimized VGS were compared.At last,monoglycerides were embedded with the three optimized VGS.The research results are as follows:Firstly,the gelatinization process of normal maize starch(NMS)in different ethanol was simulated by Differential Scanning Calorimeter(DSC).It was found that with the increase of ethanol concentration,starch gelatinization enthalpy decreased gradually,when the ethanol concentration was 70%,the gelatinization enthalpy totally disappeared,indicating that the starch gelatinization and swelling might be completely suppressed under that condition and VGS with complete granular morphology was most likely to form.Therefore,the amplification reaction was carried out in 70% ethanol,and the changes of granular morphology,crystal transformation,short-range molecular order,ethanol residue,cold-water viscosity and molecular weight of starch in 70% ethanol aqueous solution were studied at different temperatures.Results showed that the dispersion of starch was inhibited and the granular morphology could be retained under 80℃～160℃ in 70% ethanol,as the reaction temperature increased,the Maltese cross of starch disappeared gradually,the A-type crystal transformed to V-type,and short-range order of modified starch was reduced.That showed 70% ethanol did not inhibit the gelatinization of starch,the melting of the double helix structure(endothermic reaction)occurred simultaneously with the formation of ethanol-amylose V-type crystal structure(exothermic reaction),which led to no observed heat flux change in the DSC.When the reaction temperature exceeded 150℃,starch began to degrade.The cold-water viscosity of VGS reached maximum at 140℃(1932.00 c P),and it was also found that cold-water viscosity was positively correlated with the crystallinity of VGS.Then,the effects of amylose and ethanol on the formation of VGS were investigated by comparing the control group of waxy maize starch without amylose in 70% ethanol and the control group of NMS in ethanol-free water system,the effect of ethanol washing before drying on the formation of VGS was also investigated.Results showed that the waxy maize starch without amylose exhibited an amorphous structure and the granular morphology was disappeared after modified by ethanol-aqueous heat treatment,which showed the waxy maize starch could not form the VGS.The granular morphology of NMS disappeared after modification of ethanol-free water heat treatment,but there was a weak V-type crystal structure,which was formed by ethanol washing before drying,and ethanol washing before drying could reduce the agglomeration of VGS granules and enhance the crystallinity of V-type crystal,the VGS washed with ethanol had more complete granular morphology and better paste properties.It could be found that in the process of the formation of VGS,on the one hand,ethanol helped to inhibit the swelling of starch granules to maintain the integrity of the starch granules,and on the other hand,ethanol could form the V-type crystal with amylose.Next,VGS was prepared from NMS in 50%,60% and 70% ethanol,respectively.The preparation conditions of VGS were optimized by using cold-water viscosity and V-type crystal crystallinity as indexes.The results showed that the V-type crystal started to form at 90℃,100℃and 110℃ in 50%,60% and 70% ethanol,respectively.The optimal VGS preparation temperatures were 100℃,130℃ and 140℃,and the starch concentration was 20%.The coldwater viscosity and V-type crystallinity of VGS obtained in 50%,60% and 70% ethanol were2078.00 c P/24.88%,2507.33 c P/28.41% and 1932.00 c P/28.71%,respectively.In addition,compared with NMS,the water absorption and oil absorption capacity of the three optimal VGS were significantly improved,and all optimized VGS was easy to regenerate.The optimal VGS formed at 50% ethanol concentration(E50-100℃-20%)had larger specific surface area and pore volume,and had better oil adsorption performance.The granular morphology of the optimal VGS formed at 70% ethanol concentration(E70-140℃-20%)was the closest to that of the NMS,and it was easier to regenerate.Finally,three optimal VGS prepared at three ethanol concentrations were used as carriers for the embedding of monoglycerides.With amylose content,crystallization of V-type crystal and the thermodynamic properties of compounds(melting enthalpy)as indexes,compared the monoglycerides embedding differences in adsorption of three optimal VGS in different ethanol concentrations,temperatures,times,and the embedding ratios,the results showed that the three optimal VGS can be used for rapid embedding of monoglycerides at room temperature,and VGS mainly embedded monoglycerides by forming V-type complex and adsorption.E70-140℃-20% embedded monoglycerides in the form of complex,the adsorption of monoglycerides was weak.E50-100℃-20% embedded monoglycerides mainly through the way of adsorption,forming less complex. |
