Pregelatinized starch is made by heating starch, then drying and grinding it. This creates a starch that dissolves in cold water and can thicken or gel. Pregelatinized starches are often made using drum drying or extrusion cooking in industry, but other methods are being researched. The starch slurry used in drum drying can have up to 42% solids, but it’s recommended to use a moisture content greater than 70% and a temperature of 90-95°C to get the best results.
Pregelatinized starch particles look different from regular starch particles and have less of their original structure. Even though some ungelatinized particles may be present in commercial preparations made through drum drying, they generally have fewer properties that swollen particles have. During drum drying, the starch particles go through depolymerization and lose some of their weight. Drum-dried products have slightly less viscosity compared to their original starch form. Paste made with pregelatinized starch may look dull or grainy. Heating a dispersion of pregelatinized starch can create thicker paste. Modified starch can be used to enhance the properties of pregelatinized starch.