Study On Synthesis,Properties And Application Of Acetate Rice Starch

Rice,one of the most important rations in the world,has a long planting history,a wide planting range,a large area and a high yield.It is a very valuable biological resource.In the rice production process,the bursting waist rate is high,resulting in a large number of broken rice.The structure and chemical properties of these broken rice are same as that of the whole rice,but those utilization rate is very low,resulting in a great waste of resources.In addition,there will be a large number of outdated grain reserves every year,which is also an urgent issue to be solved.With the continuous progress of science and technology,the physical and chemical properties of rice starch cannot meet the needs of industrial production.It is necessary to modify rice starch to produce modified starch with good quality.In this paper,acetate starch was synthesized from rice starch.The properties and applications of rice starch before and after modification were studied in order to provide some theoretical basis and data support for the follow-up research and development of rice starch.Specific research contents and results are as follows:Using rice starch?rice starch oxidized by sodium hypochlorite?as raw material,Na2CO3 and NaOH as alkalinizer,anhydrous ethanol as wetting agent and acetic anhydride as acetylating agent,the synthesis method of acetate rice starch by finite solvent method was discussed.Fourier transform infrared spectroscopy?FTIR?,X-ray diffraction?XRD?,scanning electron microscopy?SEM?,differential scanning calorimetry?DSC?and thermogravimetric analysis?TGA?were used to analyze the structural characteristics of acetate rice starch.Response surface methodology was used to determine the optimum conditions for the synthesis of acetate rice starch by limited solvent method:m?Na₂CO₃?:m?NaOH?=3:7,m?oxidized starch?:m?alkali?:V?acetic anhydride?:V?anhydrous ethanol?=5:1:2.5:1.5,reaction temperature 70 C,reaction time 2.5 h.The conditions for preparing acetate starch with different degrees of substitution are DS=-0.15386+0.20359A+0.074608B+0.11100C+0.10737D-0.08125AB+0.025625AC+0.03437AD+0.016BC-0.001875BD+0.0056CD-0.1412A²-0.036367B²-0.027717C²-0.049557D².The degree of substitu-tion of acetate rice starch can be well controlled by the finite solvent method.FTIR results showed that acetyl group was introduced into oxidized starch by acetylation.XRD and SEM results showed that acetylation caused serious damage to starch granule structure,and high degree of substitution acetate starch had disordered crystalline structure.DSC and TGA results showed that the thermal stability of oxidized starch decreased after acetylation,which was beneficial to the application of acetate starch.By comparing the properties of acetate starch?with different degrees of substitution and raw materials?,such as retrogradation,transparency,freeze-thaw stability,gelatinization and rheology,the properties of acetate starch were analyzed.The results showed that the acetylation of rice starch could effectively reduce the gelatinization and gelatinization temperature,and improve paste transparency,freeze thaw stability,aging resistance,paste thermal stability and gel strength.The properties of acetate starch from different raw materials are different.Acetate starch from cassava and rice is better than corn.Acetate starch and hydroxypropyl distarch phosphate with better freeze-thaw stability and carboxymethyl starch with high transparency and viscosity were selected to be used in combination.The properties of three kinds of modified starch and compound modified starch were compared and their applications in dough were studied.The results showed that compound modified starch could synthesize the advantages of modified starch,and its properties were more comprehensive than single modified starch.Among them,1:2:1 group?acetate rice starch:carboxymethyl starch:hydroxypropyl distarch phosphate?showed the best performance,and the transparency,freeze-thaw stability and other properties were superior to other groups.In the application research of dough,adding compound modified starch can effectively improve the water holding capacity and texture characteristics of dough,and improve the sensory quality of cooked dough.The optimum dosage of compound modified starch is 5%-7.5%.