a gel. The following molecular associations can occur: amylose-amylose, amylose-amylopectin, and amylopectin-amylopectin. A mild association amongst chains come together with water still embedded in the molecule network. Due to strong associations of hydrogen bonding, longer amylose molecules (and starch which has a higher amylose content) will form a stiff gel. Amylopectin molecules with longer branched structure (which makes them more similar to amylose), increases the tendency to form strong gels. High amylopectin starches will have a stable gel, but will be softer than high amylose gels. Retrogradation restricts the availability for amylase hydrolysis to occur which reduces the digestibility of the starch. Pregelatinized starch Pregelatinized starch (Dextrin) is starch which has been cooked and then dried in the starch factory on a drum dryer or in an extruder making the starch cold-water-soluble. Spray dryers are used to obtain dry starch sugars and low viscous pregelatinized starch powder. Determination A simple technique to study starch gelation is by using a Brabender Viscoamylograph. It is a common technique used by food industries to determine the pasting temperature, swelling capacity, shear/thermal stability, and the extent of retrogradation. Under controlled conditions, starch and distilled water is heated at a constant heating rate in a rotating bowl and then cooled down. The viscosity of the mixture deflects a measuring sensor in the bowl. This deflection is measured as viscosity in torque over time vs. temperature and recorded on the computer. The viscoamylograph allows us to observe: the beginning of gelatinization, gelatinization maximum, gelatinization temperature, viscosity during holding, and viscosity at the end of cooling. Differential scanning calorimetry (DSC) is another method industries use to examine properties of gelatinized starch. As water is heated with starch granules, gelatinization occurs, involving an endothermic reaction. The initiation of gelatinization is called the T-onset. T-peak is the position where the endothermic reaction occurs at the maximum. T-conclusion is when all the starch granules are fully gelatinized and the curve remains stable. See also Dextrin References External links Food Resource, Starch, Oregon State University Corn starch gelatinization, filmed with microscope, Youtube Starch Food science Chemical bonding