Study On The Synthesis And Properties Of Hydroxypr-Opyl Tapioca Starch With High Molar Substitution

Using the method of Ethanol hydroxypropyl tapioca starch with high molar substitution was synthesized and the influence factors for the etherealzing reaction such as dispersing agent, catalyst, raw material ratio, reaction temperature and time etc. were discussed in detail; The effect of hydroxypropylation on the properties of tapioca starch paste was studied at different molar substitution(MS). Freeze-thaw stability , transparency and the properties of flocculation of the modified starches were compared. The granule appearance and crystal structure of hydroxylpropyl starch were studied at different molar substitution with scanning electron microscopy and X-ray diffraction. The effect of factors on the apparent viscosity of hydroxypropylated tapioca starch with high substitution solution was studied. The experimental results show that the molar substitution of the product increases as the reaction temperature, time and the dosage of 1,2-Epoxypropane raises, reaction rate quickens with the increase of catalysts concentration but the molar substitution of the final products has no obvious difference, and starting molar substitution of the product increases and after that the molar substitution reduces as dispersing agent content increases . The freeze-thaw stability and transparency of the hydroxypropylated tapioca starch paste were improved. The modified starch weth higher MS, dissolved in water. When the solution was heated, it turned turbid, then flocculated to a curd. The results indicated that the hydroxylpropylation occurred in the amorphous regions from the surface of a granule at the beginning, hydroxylpropylation produced some surface corrosion on the granules , and the gelatinisation temperature decreased with the increase of molar substitution. The effect of high substitution on the apparent viscosity was obvious, but PH value is not. Consistency and temperature influenced the apparent viscosity remarkably, of hydroxypropyl tapioca starch paste with high molar substitution. The apparent viscosity increases as the consistency raises, but the apparent viscosity decreased as temperature raises. The bigger the apparent viscosity of samples is, the bigger the apparent viscosity of it with the increase of temperature is. Hydroxypropylated tapioca starch with high substitution solution had shear-thinning nature. Those factors affecting the apparent viscosity must be considered in processing.