| Purple sweet potato(Ipomoea batatas(L.)LAM)is a sort of crops,which contains a great many of nutrients and many active substances.It is not suitable for storage,so it is prone to corruption and mildew.Not a lot of research has been done on its related products.In order to solve these problems,purple sweet potato powder is prepared by different ripening methods.The ripening method with the highest content of resistant starch was selected.Add grape seed proanthocyanidins,stevioside,guar gum and mulberry powder in it.Finally,a nutritious purple potato powder with high content of resistant starch,certain hypoglycemic effect and good taste is obtained.The main research contents are as follows:1.Four ripening methods were studied,including steaming,cooking,microwave and baking.The results showed that there was 17.8%resistant starch in the whole purple sweet potato powder after microwave curing.It is suitable to be used as raw material.SEM showed that the surface of starch granules was full of folds and gullies.The results of XRD showed that there was a strong diffraction peak at the diffraction angle of 17°.It was a typical B-type structure starch crystal.The crystallinity of purple potato powder treated by microwave was the highest.FT-IR analysis showed that-OH absorption peak appeared near 3400cm-1,and C-O-C vibration peak appeared at 1000cm-1.And the way of ripening does not affect the formation of new functional groups.DSC was used to determine the endothermic enthalpy of purple sweet potato powder samples.It is found that they all exhibit endothermic reactions.The endothermic enthalpy of microwave curing is the highest.2.To compare the contents of antioxidant activities and swelling characteristics in different purple sweet potato powder processed by four ripening methods.The results showed that the highest contents of polyphenols were steaming.And cooking had the highest contents of flavonoids and anthocyanins.All of them showed strong antioxidant activity in vitro.When the sample is cooked,the scavenging rates of DPPH and ABTS were 96.3%and 96.7%.The highest OH radical scavenging rate was obtained by microwave curing.The solubility decreases with the change of temperature,and the expansion degree is on the contrary.There was no significant difference in transparency.3.The compound powder was made by adding different proportion of grape seed proanthocyanidins.The digestive characteristics were investigated by using?-glucosidase and?-amylase.The results showed that grape seed proanthocyanidins could enhance the inhibition rate of enzyme activities related to glycemic index.The results of in vitro digestion test showed that,the GI value of compound powder is 51.2,which is a low GI food.It has good functional characteristics.4.The purpose of this chapter is to optimize the formula of nutritious purple potato meal powder.The amount of purple potato powder and grape seed proanthocyanidins remained unchanged,but change the amount of stevioside,guar gum and mulberry powder.Single factor experiments is used as the basis.The results showed that the content of Based on a Box-Behnken design,the dependent variable was the total score of sensory evaluation,were obtained to opti-mize the formula.The optimal formula for determining nutritional purple potato meal powder is as follows:15g microwave-cured purple potato powder,0.6g grape seed proanthocyanidins,0.06g steviol glycosides,4.96g mulberry powder,0.2g guar gum. |
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