| Rice is one of the most important cereal crops in China. Due to its fragility and lack of the processing technology, it will generate a large amount of broken-rice, which was primarily used as feed ingredients. The price of broken rice is much lower than the full grain, but the nutrition of the broken-rice is nearly equal to the rice. If the broken-rice can be appropriately processed and utilized, it would provide the society with infinite profits and value. Starch is a main component of the rice. Due to the physical properties defects of the natural rice starch, the application of starch has been limited and the broken-rice can be applied for preparation of modified starch to enlarge its application scope. Taking rice starch as raw material, the subject researched the carboxymethyl starch preparation. Through optimizing the reaction parameters, we obtained the optimum technology conditions. Meanwhile, the structure and properties of production were analyzed in detail. The effect of carboxymethyl rice starch as thickening stabilizer on ice-cream and the adsorption performance of carboxymethyl rice starch on lead ions were investigated. The whole research aimed to provide theoretical basis and specific methods for comprehensive development and utilization of broken-rice. Concrete study is as follows.The influences of various reaction parameters on synthesis were analyzed, and the optimum process conditions of carboxymethyl starch were got by orthogonal experiment on the basis of single factor experiment. Optimal DS of 0.72 was achieved at when the molar ratio of Na OH/AGU and MCA/AGU were 2.05 and 1.371, alkalization was proceeded at 50℃ for 0.5 h, carboxymethylation was performed at 60 for 3h, the water content was optimal at 4%(v/v), respectively. The s℃ tructure of production was evaluated by some methods such as XRD,FTIR and SEM.The main physicochemical property of carboxymethyl rice starch and rice starch were studied and compared. The result showed that the freeze-thaw stability, Transparency, retrogradation, swelling, solubility, viscosity, anti-aging ability and gel stability of carboxymethyl rice starch significantly increased, and its gelatinization temperature, gel strength were reduced. At the same time, the substitution degree of carboxymethyl rice starch has a certain influence to its physical-chemical properties. The performances increased with the substitution degree.The application effect that carboxymethyl rice starch which was prepared in the laboratory as a thickening stabilizer was added to the ice-cream was preliminary explored. The results showed that as thickening stabilizer in ice-cream, carboxymethyl rice starch can significantly improve the quality characteristics of ice-cream. When the addition amount of carboxymethyl starch was 0.3%, the expansion rate of ice-cream was greater than 90%, and the product displayed better anti-melting capacity, appearance and taste.In addition, the adsorption performance of carboxymethyl rice starch on lead ions was investigated by static adsorption experiment. Specific research contents including the effects of solution p H, adsorption time, and initial concentration of the lead ions to adsorption capacity and the adsorption kinetics and isothermal adsorption curve were studied. The results showed that adsorption equilibrium time was 40 min, the suitable solution p H = 7. The fitting result showed that reaction kinetics in the adsorption process could be well described by the equation of the rate of diffusion in the granules. Initial concentration was positively correlated with the adsorption capacity at 298 k, 308 k, and 318 k temperature. Langmuir equation could describe the behavior of carboxymethyl starch on Pb2 + adsorption better. |
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