Effects of ultra high hydrostatic pressure on the structure and properties of starches
The structures and physical properties of ultra high hydrostatic pressurized starches were investigated. Six starches were used: normal maize, waxy maize, high amylose maize (70%), tapioca, potato, and rice. Each starch was pressurized in powder form, in 1:1 (v/w) ethanol:starch suspension, in 1:1 and 2:1 (v/w) water:starch suspension, for 5 minutes and 1 hour dwelling time at 100,000 Psi. Pasting and thermal properties were measured by using a rapid visco analyzer and a differential scanning calorimeter, respectively. The molecular weight distribution was analyzed using gel permeation chromatography with Sepharose CL2B gel followed by detecting using dual channel autoanalyzer. The crystalline pattern was studied using an X-ray diffractometer. The starch granules were observed using scanning electron microscope and polarized light microscope.;Starch, which pressurized in the presence of water, gelatinized and the amount of water controlled the degree of gelatinization. The ultra high hydrostatic pressure did not change the molecular weight distribution of the starch. X-ray diffraction studies showed that A-type diffraction pattern changed to B-type-like pattern by the pressure treatments. The DSC thermograms suggested crystalline structure changed during high pressure treatment since a new peak that resembled the retrogradation peak appeared. This agreed with the X-ray diffraction pattern change. The pressurization of powder starches resulted in higher counts of cracking on the surface of starch granules.