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The optimum conditions of enzymatic reaction was discusse,different degrees of hydrolysis (DE) samples were made by using high temperatureα-amylase hydrolyze oat starches. The DE value of oat starch-based fat substitutes was selected. the physicochemical properties and application in high-ratio cake of oat starch-based fat substitutes was studied.Oat starch was prepared by milling, defatting with n-hexane and isolating oat protein by the methed of alkali-solution and acid-isolation.The physicochemical indexes of oat starch met the standard of wheat edible starch-grade product.On the condition of substrate concentration15%, reaction time 20min, temperature 90℃, enzyme additive quantity 3.4, 5.1,6.8, 8.5,10.2,11.9, 13.6, 15.3,17U/g,the different DE values of 2.39, 116, 1.79, 2.93, 3.73, 4.11, 4.83,5.15,5.87 were made.The apparent viscosity decreased as the shear rate and the temperature increased.and the apparent viscosity was too big when the concentration of different DE value samples is high than 30%.the gel strength increased as DE values increased and concentration declined. They can not form gel when the concentration of different DE value samples is lower than 25%.The gelling point decreased as DE values increased.the different DE samples had a better linear relationship when the stress was than 1.907Pa. The gelling point of The samples whose DE value were 1.16 and 1.79 were too high, Under the condition of stress 1.2Pa,temprature 90～0℃.The water (oil) binding capacity,freeze-thaw stability , emulsibility and emulsion stability of samples decreased as DE values increased. the reeze-thaw stability , emulsibility and emulsion stability of the samples whose DE values were 4.83,5.15,5.87 were poor.The hygroscopicity,solubility,transparency of samples increased after enzymolysis.the hygroscopicity, solubility,transparency of samples increased as the DE values increased.the moisture retention was opposite.the second-order model of adsorption kinetic equation could characterize the moisture absorption(RH85%) and retention(RH38%) process very well and the relation coefficients all were higher than 0.999 8.The granule of the Oat starch were geometry contour anomalous shape,assuming the elliptic type and the edges and corners. "+"-shape polarization crosses can be observed apparently,the umbilical point was at the center of starch granules.The crystalline structure is A-type.After enzymolysis,the shape of granule varies, like the anomalous chippings, having the obvious edges and corners, the surface have the cavitypit and the damage.polarization crosses properties was mainly disappeared,A-type crystalline structure was destroyed.OSFS can replace the fat in high-ratio cake well, OSFS whose DE value were 2.39, 2.93, 3.73 were good fat substitute.OSFS whose DE value was 2.39 was the best fat substitute.OSFS of the density is 25% can succeed replace the fat within 40% in high-ratio cake, 20% for best fat substitution quantity,according to Appearance, physicochemical parameters and texture of the cake.
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