Study The Gelatinization Characteristics Of Rice For Different Milling Fractions

Rice has an important position in the world, it maintains the grain ration for most of the Asian. Rice is rich in nutrients, such as sugar, protein, fat, fiber, vitamins and minerals, etc. Brown rice can be obtained after husking off the shell. In rice milling process, according to the quality standards of the finished product we give different levels of the bran layer save. At present, the rice processing of China blind pursuit of "fine, slender, white", ignore the nutrition, environmental protection and energy saving, make the resource consumption and nutrition loss seriously. Presently commercially available white rice grinding to rice bran is in commonly 10%～15%. As a result, the moderate processing of rice is of great significance. Because many of protein, fat and dietary fiber can saved in moderate processing rice, it can influence the gelatinization, cooking quality, texture and flavor of the rice. Therefore, study of the moderate processing rice is imperative.In this paper, we maked early indica rice (De Nong 108), late indica rice (Wai Yin 7) and japonica rice (Kong Yu 131) as raw materials to product rice of various precision. By studying the influence of protein, fat and dietary fiber on the pasting properties, we can discussed and make a comprehensive analysis on the pasting properties of rice in different precision. The results are as follows:(1)Making the late indica rice (Wai Yin 7) as raw material, preparation of grinding the reduction rate was 20% of the rice. Then added some gradient of rice protein (0%,5%,6%,7%,8%,7%) to the rice flour, by measuring its change of swelling power, solubility, viscosity, thermodynamic properties and morphology, we can analysis the effect of rice protein on pasting properties of rice. Results are as follows:With the rice protein adding amount in rice flour increased, the swelling power, solubility, peak viscosity, trough viscosity, breakdown value and final viscosity of rice flour displayed a decreasing trend, on the contrary, the setback, gelatinization temperature, gelatinization enthalpy value and peak time of ice flour presented a increasing trend, morphology as a uniform form became into a mesh structure with holes after the rice flour pasted. All of these showed that in the process of pasting, the rice protein can play a protective role of starch particles, it can not only form a protective film in the surface of starch granules, but also formed hydrogen bond or disulfide bond with amylose, and influenced the gelatinization of rice flour.(2)Making the late indica rice (Wai Yin 7) as raw material, preparation of grinding the reduction rate was 20% of the rice. Then added some gradient of dietary fiber (0%,1%,2%,3%,4%,5%) to the rice flour, by measuring its change of swelling power, solubility, viscosity, thermodynamic properties and morphology, we can analysis the effect of dietary fiber on pasting properties of rice. Results are as follows:With the dietary fiber adding amount in rice flour increased, the swelling power, solubility and gelatinization enthalpy value of rice flour increased first and then decreased, the peak viscosity, breakdown value and final viscosity of rice flour displayed a decreasing trend, on the contrary, the setback and gelatinization temperature of rice flour presented a increasing trend, morphology as a uniform form became into clusters of structures with holes after the rice flour pasted. All of these showed that in the process of pasting, dietary fiber can compete water with starch molecules because it has good water binding capacity and swelling power, inhibited and blocked the reaction of starch with water molecules, thus restricted the expansion of the starch and the associated pasting reaction. At the same time, dietary fiber can also interact with starch, and influenced the gelatinization of rice flour.(3)Making early indica rice (De Nong 108), late indica rice (Wai Yin 7) and japonica rice (Kong Yu 131) as raw materials, preparation of grinding the reduction rate were 0%,2%,4%,6%,8%,10% of the rice. By measuring its change of swelling power, viscosity, thermodynamic properties and morphology, we can analysis the pasting properties of rice for different precision. Results are as follows:For different varieties of rice in different precision, its swelling power, viscosity, and thermodynamic properties all had certain difference. This is due to the different varieties of rice had different composition and structure, then leaded to have different gelatinization characteristics.For the same variety rice of different processing precision, with the increase of grinding rate reduction, its swelling and gelatinization enthalpy increased first and then decreased, the peak viscosity, breakdown and final viscosity presented a increasing trend, and setback and gelatinization temperature presented a decreasing trend, its morphology also had some change. All of these showed that the machining accuracy for rice of same variety, as the grinding rate reduction is different, it contains different protein, fat and dietary fiber content, these compounds have certain influence on rice gelatinization, combination impact make the rice of different machining precision present different gelatinization properties.