Study On Dry Preparation Of Oxidized Starch Using Peracetic Acid Strengthened By Mechanical Activation And Its Property As Builder

Sodium tripolyphosphate(STPP)used in detergent caused the problem of eutrophication in rivers and seas.Recently,STPP has been forbidden to be used in detergent all around the world,and people have been finding a new builder which can take the place of STPP in the detergent industry.When starch is oxidized,its properties and structures are greatly different from native starch.Oxidized starch is widely used in making paper,food,drug etc.As a builder,oxidized starch has the properties of complexing calcium ions,dispersing dirt,restraining the crystallization of calcium carbonate,so it is expected to take the place of STPP.However,the crystal structure in native starch can block the reaction between reagents and starch.Therefore,how to improve the reaction efficiency of starch is an important issue.In this study,oxidized starch was produced by mechanical activation-strengthened dry process with using cassava starch as raw material,peracetic acid as oxidant,CuSO4·5H20 as catalyst,concentrated hydrochloric acid as acidulant,and self-designed stirring-type mill as solid-phase reactor.The influences of reaction temperature,reaction time,dosages of oxidant and catalyst,etc.were investigated respectively by using carboxyl content of oxidized starch as evaluating index.The particle morphology,crystal structure,functional groups,pasting properties,and Brabender viscosity were determined by scanning electron microscopy(SEM),X-ray diff:raction(XRD),Fourier transform infrared spectroscopy(FTIR),differential scanning calorimeter(DSC),and Brabender viscoamylograph,respectively.The solubility and diaphaneity of oxidized starch,and the properties of oxidized starch as a builder such as complexing calcium ions,dispersing dirt and restraining the crystallization of calcium carbonate were also investigated.The conclusions are as follows:(1)The results show that the oxidation reaction of cassava starch was considerably enhanced by mechanical activation-strengthened dry process,resulting to the increase of carboxyl content of oxidized starch.The optimal parameters for the preparation of oxidized starch are:dosage of oxidant 3.84%,reaction time 60 min,reaction temperature 50?,dosage of catalyst 0.03%and dosage of hydrochloric acid 0.34%.Under these conditions,the carboxyl content of oxidized starch was 1.826%.(2)The SEM analysis indicates that starch granules were destroyed by mechanical activation and oxidizing reaction.The FTIR analysis indicates that starch was oxidized successfully,showing that carboxyl was a new group appeared in the product.XRD analysis shows that the starch crystallinity was reduced by mechanical activation,leading to the enhancement of oxidizing reaction between oxidant and starch.The viscosity of oxidized starch was far lower than native starch.The more carboxyl content,the higher solubility and transparency.(3)The results show that the more carboxyl content,the stronger complexing capacity of oxidized starch.When the oxidized starch was blended with 4 A zeolite,the complexing capacity of this mixture was stronger than oxidized starch.The oxidized starch exhibited favorable dispersing property,which was increased with the carboxyl content of oxidized starch.To some extent,oxidized starch could restrain the crystallization of calcium carbonate.