A Study of Starch Granular Aggregation

Abstract

The aggregation behavior of starch granules during cooking was investigated. Granular aggregation was found to depend mainly on water content and degree of conversion (cooking) of starch. There were threshold values of water content and degree of conversion for powdery starch to undergo a phase transition from a nonaggregated to an aggregated state. A method for determining such threshold values of the transition was developed. A mathematical model was also developed to describe the aggregation behavior of cooked starch. Its potential application to food systems, especially to the simulation of starch extrusion process, was discussed.

Modeling Shearing Resistance of Powdery Starch for Simulation Studies of Extrusion Cooking Processes

“…These equations have been used to describe kinetics of starch cooking processes in a single screw extruder, in a capillary rheometer [10][11], and in a twin screw extruder [12]. Recently, the conversion of starch [20] rate 0 to 550 s -1 , starch conversion 0 to 0.36 (36 %), and normal pressure 0 to 83 kPa) parameter values in each functionality were evaluated. A single mathematical model useful for calculating shear stress was obtained by combining these effects in a single relationship.…”

Modeling of transport phenomena and melting kinetics of starch in a co‐rotating twin‐screw extruder

“…Thus, the bulk density of the solid particle bed in the conveying section was determined by (16) As the selected screw had a tapered shape, the volumetric flow rate V z , which was calculated by Equation (14) decreased along the downstream channel, resulting in an increase in bulk density of the solid particles. The screw finally became completely full.…”

“…Rauwendaal 9 reported that a minimum volume of polymer melt has to be available to fill the space between the solid particles before the solid particle flow becomes a non-Newtonian melt flow. Wang et al 16 found that the powdery raw starch became interconnected and behaved like a fluid when the percent conversion of starch reached about 37%.…”

“…The bulk density of the solid particle bed was then determined by Equation (16). The temperature distribution in the particle was predicted by Equations (38), (41), and (43).…”

“…At the beginning of melting, the material was still in a particle form and heat transfer from the hot barrel contributed to the latent heat of melting. When the melt to particle fraction reached a critical value (37% for starch given by Wang et al 16 ), the space between particles became filled by melt and the particle flow becomes a non-Newtonian melt flow. The heat transfer from the hot barrel and the heat of viscous dissipation in the melt matrix continued to melt the remaining part of particles, increasing the melting rate.…”