Publication: Effect of osmotic pressure on starch: New method of physical modification of starch
Issued Date
2007-02-01
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ISSN
1521379X
00389056
00389056
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2-s2.0-33847340240
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Mahidol University
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SCOPUS
Bibliographic Citation
Starch/Staerke. Vol.59, No.2 (2007), 78-90
Suggested Citation
Chirdchan Pukkahuta, Sujin Shobsngob, Saiyavit Varavinit Effect of osmotic pressure on starch: New method of physical modification of starch. Starch/Staerke. Vol.59, No.2 (2007), 78-90. doi:10.1002/star.200600509 Retrieved from: https://repository.li.mahidol.ac.th/handle/20.500.14594/24032
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Title
Effect of osmotic pressure on starch: New method of physical modification of starch
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Abstract
A new method of physical modification of starch in the presence of high concentrated salt solution is presented, called "Osmotic Pressure Treatment" (OPT). OPT was introduced in order to produce the same physically modified products as obtained by conventional heat-moisture treatment (HMT) of starch. Potato starch was selected for the comparative study of the two methods. For the OPT method, potato starch was suspended in a saturated solution of sodium sulfate and heated in an autoclave at 105°C and 120°C, which corresponded to the calculated osmotic pressures of 328 and 341 atm (332 and 345 bar, respectively) (assuming sodium sulfate dissociates completely) for 15, 30 and 60 min, respectively. For the HMT method, starch with 20% moisture content was placed in a Duran bottle, then the same heat treatment method in the autoclave was applied. Light and scanning electron microscopy (SEM) showed that OPT of starch changed the shape of the starch granules to a folded structure, while the starches remained unchanged after HMT. The RVA viscogram for the OPT starch exhibited a decrease in the peak viscosity without a breakdown and an increase of the pasting temperature when increasing the temperature and time, which was in an agreement with the viscosity patterns for the HMT starches. X-ray diffraction patterns were altered from B to A+B for the HMT and from B to A type for the OPT starch when treated at 120°C. After OPT, the gelatinization temperatures (To, Tp, and T c) of the starch increased significantly with increasing temperature and time, whereas only the Tc of starch increases after HMT. The biphasic broadening of the peaks (high Tc-To) can be explained by an inhomogeneous heat transfer during HMT. Narrow peaks in the DSC curve can be an indication for a better homogeneity of the OPT samples. However, both methods provide a similar decrease in the gelatinization enthalpy (ΔH). The amylose-amylopectin ratio calculated from the HPSEC patterns was strongly increased for HMT starches at 105°C for 60 min and 120°C for 30 min and decreased after treatment at 120°C for 60 min. For OPT starches the ratio was strongly increased at 120°C for 15 min and decreased after prolong heating. The OPT provides a uniform heat distribution in the starch suspension. This allows the modified starch to be produced on a larger scale. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.