Influence of Rice Variety and Freezing on Flour Properties

Abstract

Two rice varieties were used to study the effect of freezing and grinding processes on rice flour properties. The freezing and grinding processes followed by sieving mainly affected the particle size distribution, starch damage, and amylose content of flours. In case of both rice varieties, the percentage of fine particles increased in the flours obtained from frozen rice. Freezing caused the increase of the flour yields from 45.5–50.9% to 54.6–56.5% and the decrease of the flour fineness modules. Moreover, the amylose content and starch damage registered changes when grinding frozen rice, but in case of those parameters, the values are influenced additionally by the native starch properties of variety and most probably by the texture of the endosperm. The swelling power, water solubility index, and gelatinization temperature were higher in flour from frozen rice compared to the flour from non-frozen rice. The modifications generated by rice freezing prior to grinding resulted in increased mechanical properties and decreased thermo-mechanical weakening of proteins. The hardness of the gel was directly correlated with the amylose content, while the freezing process led to the increase of the dough breakdown and starch retrogradation.

Keywords

• rice
• freezing
• grinding
• damaged starch
• hydration properties
• gel texture