On the Dispersion and Small-Amplitude Oscillation Measurements of High Amylopectin Potato Starch
| Main Authors: | , , |
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| Format: | Article |
| Language: | English Slovak |
| Online Access: | http://www.viks.sk/chk/star_3_4_03_121_130.doc |
| Abstract: | Summaries. Differential scanning calorimetry (DSC), optical microscopy and turbidity measurements were used to define experimental conditions (time, temperature and shearing) for dissolving high amylopectin potato starch (HAPP) granules. A simple, less time consuming and non-chemical method for preparing starch samples was established. Small-amplitude oscillation measurements were used to characterise the behaviour of the resulting solutions. The DSC, microscopy and turbidity experiments showed that preparing the samples at 140 °C was necessary to dissolve HAPP, with no further detectable granule structures. Rheological measurements showed that the storage (G) and loss (G") moduli increased with concentration. At a HAPP concentration of 2 % G" > G' and the system behaved like a diluted solution. The frequency dependence also decreased with increasing concentration. At 14 % HAPP, the system showed more gel-like properties with G more or less independent of frequency. Conclusion. It has been shown, by DSC, microscopy and turbidity measurements, that 140 °C was the most appropriate temperature for reducing the influence of granules in HAPP samples on the rheological measurements. At this temperature, no granule structures were detected in the microscope. In the small-amplitude oscillation measurements, the system proved to be stable with time, showing no syneresis. In addition, the moduli showed a concentration dependence, and the concentration where G was larger than G" was beyond 10 %. At concentrations higher than 10 %, the system behaved more gel-like than at lower concentrations. For all concentrations, G and G" converged with increasing frequency. At concentrations lower than 14 %, the frequency dependence decreased with increasing HAPP concentration. In addition, G and G" augmented with increasing concentration. In the concentration range 2-14 % HAPP, diluted solution to gel-like behaviour was observed. We have also shown that when the granules or granule structures are eliminated, the frequency of the 2 % HAPP sample is changed from that corresponding to a weak gel (sample prepared at 90 °C) to the one of a diluted solution (sample prepared at 140 °C). |
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| ISSN: | ISSN 0038-9056 |
