Study On Preparation And Properties Of Cross-linking Hydroxypropyl Compound Modified Starch

The preparation of cross-linking hydroxypropyl starch with low substitution degree was studied by using corn starch as material, the phosphoryl chloride as cross-linking reagent, the propyleneoxide as ether reagent, sodium hydroxide as catalyst, sodium sulfate as swelling inhibitor in this paper. The effect of factors such as amount of sodium hyhydroxide, amount of propylene oxide, amount of phosphoryl chloride, amount of sodium sulfate, reaction temperature, reaction time, pH value and starch milk concentration on the cross-lingking reaction and etherization reaction was discussed. The substitution degree of cross-linking hydroxypropyl starch measured by the spectrophotometer method, and the cross-linking degree by the centrifugal method. The results showed that the substitution degree of cross-linking hydroxypropyl starch increases with the increase of amount of propylene oxide, but its reaction efficiency decreases. The cross-linking hydroxypropyl starch DS increases with increasing reaction temperature, reaction time and amount of sodium hydroxide under certain conditions. With increasing amount of sodium hydroxide the double modified starch DS increases when its amount is small. Whereas decreases when its amount is big. Raising starch milk concentration and reaction time also increases cross-linking degree of starch. And pH value and reaction temperature influences evidently cross-linking reaction.The properties of corn starch, cross-linking starch, hydroxypropyl corn starch and cross-linking hydroxypropyl compound modified starch with different substitution degree were compared. The results showed that the acid-resisting of starch could be improved greatly by cross-linking reaction. The paste transparence and freeze-thaw stability of starch could be increased by etherization reaction. The cross-linking hydroxypropyl starch has better properties in freeze-thaw stability, paste transparence and acid-resisting than that of original starch. With the increase of cross-linking hydroxypropyl starch DS, itsgelatinization temperature decrease gradually, but its the viscosity, expansion degree, paste transparence and freeze-thaw stability go up gradually.The cross-linking hydroxypropyl compound modified starch was applied in the confiture and beverage as stabilizer and thickener. They reduce greatly the cost of confiture and beverage, and keep flavour, thickness and mouth sense.