Physical Basis for Separation of Rice Starch using Various Density Gradient Systems and its Effect on Starch Recovery, Purity, and Pasting Properties
| Main Authors: | , , |
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| Format: | Article |
| Language: | English Slovak |
| Online Access: | http://www.viks.sk/chk/star_10_03_450_456.doc |
| Abstract: | Summaries. A 32% waxy and non waxy rice flour slurry containing starch-protein agglomerates was physically disrupted in presence of water by use of high pressure homogenizer called Microfluidizer(R). Microfluidized rice flour slurry from passes 2 and 4 was collected followed by isolation of starch using three different density gradient solutions/systems (CeCI, NaCI/sucrose and ZnSO4-7H2O). Complete deagglomeration was obtained after passing the rice flour slurry four times through the Microfluidizer(R). The recovery of isolated starch varied from 76.28% to 91.20% for different density gradient systems. The degree of deagglomeration did not seem to affect recovery but affected the purity of the isolated starches. All starches produced from pass 4 rice slurry resulted in starches with residual protein below 0.5%. Higher density of the gradient solution resulted in higher recovery and purity of starch. The isolation method had a significant effect on the pasting properties of the isolated starch. Residual protein in isolated starch had a negative correlation with peak viscosity and setback of pass 2 waxy and non-waxy starches. The salts were retained in purified starch despite rigorous washing (at least 75 times greater than the control) and could affect starch properties. Conclusions. Density gradient systems could be used to isolate starches with low protein content from deagglomerated rice flour slurry. Density gradient separation of rice starch and protein is directly dependent on the density of the gradient system/solution. A higher density of the density gradient system/solution will most likely improve starch recovery and purity. Salts are retained in the starch granules and affect the separation of protein and starch. Absorption/adsorption of heavy metal salts increases the density of the starch granule, thereby increasing the difference between density of starch and protein. This allows for efficient separation of starch with high recovery and purity. Cesium chloride resulted in highest recovery of starch. This absorption/adsorption could affect starch pasting properties and also the starch structure. Density gradient system can only be used to conduct preliminary physical studies regarding recovery and purity of starch or level of deag-glomeration until more conclusive data is obtained on its effect on starch structure. Density gradient system/solution can be used to screen rice varieties coming for processing. |
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| ISSN: | ISSN 0038-9056 |
