Influence of the surface/volume ratio on the rheological properties of starch dispersions

Abstract

This study aims to evaluate the influence of the surface/volume granule ratio of amaranth, corn, and potato starches on the rheological properties of pastes and gels obtained at 5 and 10% solids concentration through granulometry, scanning electron microscopy, rotational, and dynamic rheological measurements. The granule size distribution and the surface/volume ratio drove the rheological behaviour as a function of temperature and concentration. At a concentration of 10%, the consistency index of corn starch (CS) paste was 147.25 Pa.sn (n - flow behavior index), a higher value compared to pastes from potato starch (PS), 86.54 Pa.sn, and amaranth starch (AS), 44.48 Pa.sn. The lowest values of the loss angle tangent (Tan δ) in CS (0.052 and 0.035) at both solids concentrations suggested a better gel conformation. Noticeable changes in consistency index and storage modulus were observed in CS. A theoretical analysis of the surface/volume ratio change showed that CS reached a 2.2 value, much lower than the 4.5 and 5.8 values for PS and AS, respectively. These findings provide additional criteria for the food industry when choosing starches with suitable rheological behaviour as a function of surface/volume granule ratio and solids concentration.

Keywords

• granulometry
• pasting properties
• polymer gels
• rheology
• solids concentration