Retrogradation Properties Of Maize, Waxy Maize And Proso Millet Straches Gelatinized By Ultra High Pressure

Starches can be modified chemically or physically or both and enzymatic to accentuatetheir positive characteristics, diminish their undesirable qualities, or add newattributes.Considering the food safety, physical modification means has become a new hotspot.Compared to other physical modification means, the ultra high pressure (UHP) technology issafer, more stable and energy-saving. In this paper, maize, waxy maize and proso milletstarch–water suspension (50%) was submitted to different levels treatment for15min, andchanges in the structure, morphology and some physicochemical properties of starch wereinvestigated. Additionally, the retrogradation properties of the three kinds of starchesgelatinized by UHP stored for0h,3h,6h,12h,24h,2d,4d and8d have been observed. Themain results indicated as follow:1. The particle morphology of maize, waxy maize and proso millet starch is mostlyspherical and polygonal. The particle size of waxy maize starch was maximal, and the particlesize of millet starch is minimal. Under lower pressures, there was no significant change inmorphology, polarization cross and the crystal structure. indicating changes caused mainlyinternally. The changes caused by600MPa were including a complete loss of birefringence,the ordered crystallite structural disruption of the starch granules and the transformation fromthe A–type X–ray patterns to B–type–like pattern. Meanwhile pressure of600MPa caused100%of gelatinization for maize, waxy maize and proso millet starch.2. Under the same conditions, the most obvious aging phenomenon was detected in themaize starch, and the degree of retrogradation of wazy maize starch was the least. The kineticequation showed that recrystallization of three high-pressure gelatinized starch was oncegrown nucleation (n <1), and the aging rate of maize starch was highest, followed by prosomillet and waxy maizestarch, which matched with the measurement results of X-raydiffraction and DSC methods.3. In the aging process, peak viscosity, viscosity and final viscosity of threehigh-pressure gelatinized starch were significantly reduced, while there was no significantunified changes in the setback, pasting temperature and peak time of high-pressure gelatinizedstarch were significantly higher than those of native starch; the solubility and swelling power increased with aging time, but the amplification in the early time was not significant.4. The transparency of maize and proso millet starch gelatinized by UHP wassignificantly reduced with the extension of storage time, which of waxy maize starchgelatinized by UHP was decreased at first and than increased; there was no significant changein syneresis of waxy maize starch during aging time, while the syneresis of maize and prosomillet starch increased fast after24h; RS3starch content of three high-pressure gelatinizedstarch were increased with aging time, and the amplification(6.11%) of high-pressuregelatinized proso millet starch was biggest.