Effect Of Dietary Fiber Modified By Dynamic High Pressure Microfluidization On Physicochemical Properties Of Rice Starch

Dietary fiber had received widespread attention for its important physiological function, in order to further improve the biological activities of dietary fiber,many scholars did a lot of research about modification of dietary fiber. The modified dietary fiber was considered a great significance to the development and application of new type fiber fortified foods. In the present research dynamic high pressure microfluidization(DHPM)which is a promising high pressure technology was introduced to modify the main components of soybean dietary fiber which were soybean soluble dietary fiber(SDF)and insoluble dietary fiber(IDF). The changed of properties and structure of dietary fiber samples before and after DHPM treatment were determined. Investigated the effect on the properties of rice starch(RS) with addition modified soluble dietary fiber(MSDF)and insoluble dietary fibre(MIDF). The relationship between the structure changes and properties of change of modified dietary fiber would be clarified to provide basic data and theoretical basis.For the application of modified dietary fiber in starchy foods.The structure changes of IDF and SDF by DHPM treatment were:The particle size distribution of IDF was narrowed, and the average particle size decreased significantly when IDF was broken by80MPa、120MPa with DHPM treatment. The average particle size appeared increased trend when the pressure reached170MPa. When the IDF treated with DHPM, the water holding capacity increased remarkably while Weight-average molecular weight Mw was reduced. There was no new absorption peak showed in the infrared spectrograms of SDF and IDF after DHPM modification. Compared with infrared spectrograms of IDF and MIDF samples, we can see that the hydrogen bonding between molecules decreased with the increasing pressure during DHPM modified. With the increase of DHPM treatment pressure, the β-D glucoside of the sample molecules hydrogen bond fractured and absorption peak decreased. The infrared absorption peak intensity increased which was stand for adsorption in water. The infrared spectrogram of MSDF trended basically identical compared with infrared spectrum of MIDF. The microstructure of IDF and SDF before and after DHPM treatment were observed. IDF had a dense structure, internal support main body structure composed of fibrous materials, amorphous organizations were embedded in other fiber network, the form had certain thickness of the block structure. MIDF had loose structure, could obviously see that outside surface was torn, serious internal also appeared puffed and cavity and had a large cavity in cellular structure. SDF also had serious destroyed.It was investigated that swelling power, solubility, clarity, syneresis and hardness of rice starch (RS) were influenced by adding different content of these modified dietary fiber (5%,7.5%,10%, and20%; dry starch basis) with different modified pressure. The results indicated that swelling power, solubility and freeze-thaw stability of starch samples after added different content of MSDF were increased compared to that of SDF group. It was obvious that the solubility and freeze-thaw stability of rice starch with addition of SDF was significantly affected by modified pressure. The swelling power, solubility and freeze-thaw stability of RS also presented the same change trend after added MIDF. The clarity of RS increased much significantly after added MSDF than that added SDF. But the more addition of SDF or MSDF, the lower clarity value of RS. Under the same add proportion, the negative impact of the starch paste transparency significantly reduced when added with MIDF compared with which added nature IDF, with the increased content of MIDF or IDF, starch paste transparency declined significantly. The hardness of RS decreased (p<0.05) with addition SDF after7days storage under4℃, and with the content increased, the hardness fell remarkably. The hardness of RS decreased much significantly after added MSDF than that added SDF. When the amount of addition increased, the hardness of RS with IDF increased and the hardness of RS with MIDF decreased, especially MIDF treated with170MPa.It was found that added MSDF or MIDF reduced the final viscosity and setback of starch. Setback data proved that the MSDF and MIDF could inhibit the starch retrogradation behavior, and MSDF inhibited the short-term retrogradation more than MIDF. The retrogradation enthalpy value and the peak height ratio of1047cm-1to1022cm-1absorption peak of long shaped rice starch decreased with addition MSDF or MIDF. It was proved that added MSDF and MIDF inhibited the effectiveness of the long shaped rice starch retrogradation, and MIDF inhibited the long-term retrogradation more than MSDF. Added the MSDF and MIDF RS after lyophilization gel hollow cavity wall thinning, obviously the cavity becomed larger, honeycomb-like structure. It also from micro-structure to prove the freeze-thaw stability of RS was increased with addition MSDF or MIDF, and inhibited retrogradation of RS.