Effect Of Tea Polyphenols On Processing Characteristics Of Brown Rice, Its White Rice And Rice Starch

Rice processing products is single in our country, and the main form of consumption is the white rice (rice), causing the waste of a large number of edible food resources. Tea polyphenols as a safe, nontoxic, and multi-functional food additive, which has been used in the study of rice starch anti-aging properties, found that it can effectively restrain the ageing of rice starch. Therefore, the study of rice, its by-product and nutritional additives application of tea polyphenols, is favored by domestic and foreign researchers and attention increasingly. In this paper the brown rice, its white rice and rice starch of two indica rice (Huang Huazhan and Xiang late indica 13) as the research objects, research its gelatinization viscosity, freeze-thaw stability, thermal characteristics and dynamic viscoelastic effects with tea polyphenols in different conditions. These features will contribute to the development of deep processing of rice products and relevant products processing properties improved. At the same time, TPLs will be also appled to brown rice cake which is the development of new products. Main conclusions of this paper are as follows:Firstly, this paper study the pasting viscosity characteristics of brown rice, white rice, and rice starch with the tea polyphenols (TPLs) under different conditions, found that TPLs could reduce the peak viscosity, setback decreases with TPLs increasing, This suggests that TPLs could inhibit the raw material retrogradation. Adding NaCl, peak viscosity, trough and final viscosity of raw materials increased; but the breakdown of brown rice and white rice reduced, and reduced with the increase of NaCl concentration. This suggests that the NaCl can not only improve the stability of hot paste of brown rice and white rice, can also inhibit the retrogradation. On the basis of NaCl, add TPLs can make the change trend weakened, and as the TPLs increasing, the resistance to the viscosity change caused by NaCl is more obvious, that is to say, adding TPLs can keep the original viscosity features of raw materials. In rice starch samples, adding NaCl makes the viscosity curve of the rice starch irregular, this phenomenon may reflect the NaCl physical interaction with the starch in the process of heating. Adding sucrose, peak viscosity, trough and final viscosity of raw materials increased. Adding TPLs, which can change the breakdown caused by sucrose, make the breakdown of the raw material value increased, and make hot paste stability weakened. The effect of TPLs during pH 3～9 on the gelatinization viscosity properties of material is little.Secondly, the freeze-thaw stability, thermal characteristics and dynamic viscoelasticity of brown rice, its white rice and rice starch are studied. The freeze-thaw stability of raw materials increased significantly with adding TPLs, NaCl or sucrose. On the basis of NaCl, adding TPLs, the concentration of NaCl and TPLs have synergy in certain scope can improve the freeze-thaw stability of raw materials. On the basis of sucrose, adding TPLs, the freeze-thaw stability of brown rice raise, then down; the freeze-thaw stability of white rice and rice starch significantly increased with the increase of concentration of TPLs. PH value in 3～9, the freeze-thaw stability of raw materials did not change significantly. On the basis of pH, adding TPLs, the freeze-thaw stability of brown rice and rice starch raise, then down; the freeze-thaw stability of white rice increased significantly with the increase of concentration of TPLs.Thermal characteristic results of raw materials show that adding TPLs can reduce gelatinization temperature and enthalpy of three kinds of materials significantly, and the lower level is proportional to the amount of TPLs addtion. For brown rice, the TPLs provides a convenient and feasible solution for hard cooking of brown rice which is the problem restricting its use. Retrogradation characteristics analysis, found that tea polyphenols can reduce the retrogradation enthalpy and retrogradation rates significantly, and with the increase of adding amount, its inhibition effect is more apparent. The synergy of NaCl or sucrose and TPLs to the starch molecules of the samples, can inhibt the retrogradation.The dynamic viscoelastic results of raw materials show that G’ is always greater than G" in the whole test process, suggesting that the gel elasticity is greater than viscosity, it is tend to be similar to the solid gel. With the TPLs increasing, the G’ and G" of rice starch all decrease, suggesting that TPLs can reduce the elasticity and viscosity of rice starch paste. On the basis of 10%TPLs, adding 3%NaCl or 10%sucrose, G’ and G" of raw materials increase. Adding 20%TPLs, G’ and G" of all raw materials are minimum, suggesting that 20%TPLs can reduce the viscoelasticity of the raw materials.Finally, study the application of tea polyphenols in brown rice cake by single factor and orthogonal test, make sensory score and structure evaluation as indicators, to determine the optimum formula of tea polyphenols brown rice cake is:cake powder 20%(the basis is the total weight of brown rice and cake powder), tea polyphenols 0.8%, sugar 80%, milk 40%, egg liquid 180%, oil 10%, baking time for 19 min, according to the formula, producing a cake has smaller hardness, longer shelf life and stronger chewiness than ordinary.Above all, TPLs applied in brown rice, white rice and starch is feasible and beneficial. The research provides a new way for the comprehensive utilization of tea resources, also provides the theoretical basis for brown rice by-products processing.